]> gitweb.stoutner.com Git - PrivacyBrowserAndroid.git/blobdiff - app/src/main/java/com/stoutner/privacybrowser/activities/MainWebViewActivity.java
Update Download with External App summary. https://redmine.stoutner.com/issues/921
[PrivacyBrowserAndroid.git] / app / src / main / java / com / stoutner / privacybrowser / activities / MainWebViewActivity.java
index 45a1de5b1c94e2c9267c6355eeaa8e9ccf113622..1ee31db40a03cb8dfe9996eacfeaa79140aa230e 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright © 2015-2022 Soren Stoutner <soren@stoutner.com>.
+ * Copyright 2015-2022 Soren Stoutner <soren@stoutner.com>.
  *
  * Download cookie code contributed 2017 Hendrik Knackstedt.  Copyright assigned to Soren Stoutner <soren@stoutner.com>.
  *
@@ -99,6 +99,7 @@ import android.widget.RadioButton;
 import android.widget.RelativeLayout;
 import android.widget.TextView;
 
+import androidx.activity.OnBackPressedCallback;
 import androidx.activity.result.ActivityResultCallback;
 import androidx.activity.result.ActivityResultLauncher;
 import androidx.activity.result.contract.ActivityResultContracts;
@@ -118,7 +119,6 @@ import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import androidx.viewpager.widget.ViewPager;
 import androidx.webkit.WebSettingsCompat;
 import androidx.webkit.WebViewFeature;
-import kotlin.Pair;
 
 import com.google.android.material.appbar.AppBarLayout;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
@@ -153,6 +153,7 @@ import com.stoutner.privacybrowser.helpers.BlocklistHelper;
 import com.stoutner.privacybrowser.helpers.BookmarksDatabaseHelper;
 import com.stoutner.privacybrowser.helpers.DomainsDatabaseHelper;
 import com.stoutner.privacybrowser.helpers.ProxyHelper;
+import com.stoutner.privacybrowser.helpers.SanitizeUrlHelper;
 import com.stoutner.privacybrowser.views.NestedScrollWebView;
 
 import java.io.ByteArrayInputStream;
@@ -174,28 +175,28 @@ import java.text.NumberFormat;
 
 import java.util.ArrayList;
 import java.util.Date;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
+import kotlin.Pair;
+
 public class MainWebViewActivity extends AppCompatActivity implements CreateBookmarkDialog.CreateBookmarkListener, CreateBookmarkFolderDialog.CreateBookmarkFolderListener,
         EditBookmarkFolderDialog.EditBookmarkFolderListener, FontSizeDialog.UpdateFontSizeListener, NavigationView.OnNavigationItemSelectedListener, OpenDialog.OpenListener,
         PinnedMismatchDialog.PinnedMismatchListener, PopulateBlocklists.PopulateBlocklistsListener, SaveDialog.SaveListener, UrlHistoryDialog.NavigateHistoryListener,
         WebViewTabFragment.NewTabListener {
 
     // Define the public static variables.
-    public static ExecutorService executorService = Executors.newFixedThreadPool(4);
+    public static final ExecutorService executorService = Executors.newFixedThreadPool(4);
     public static String orbotStatus = "unknown";
-    public static ArrayList<PendingDialog> pendingDialogsArrayList =  new ArrayList<>();
+    public static final ArrayList<PendingDialog> pendingDialogsArrayList =  new ArrayList<>();
     public static String proxyMode = ProxyHelper.NONE;
 
     // Declare the public static variables.
-    public static String currentBookmarksFolder;
+    public static String currentBookmarksFolder = "";
     public static boolean restartFromBookmarksActivity;
     public static WebViewPagerAdapter webViewPagerAdapter;
 
@@ -234,9 +235,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
     // `findNextOnPage()`, `closeFindOnPage()`, `loadUrlFromTextBox()`, `onSslMismatchBack()`, `applyProxy()`, and `applyDomainSettings()`.
     private NestedScrollWebView currentWebView;
 
-    // `customHeader` is used in `onCreate()`, `onOptionsItemSelected()`, `onCreateContextMenu()`, and `loadUrl()`.
-    private final Map<String, String> customHeaders = new HashMap<>();
-
     // The search URL is set in `applyAppSettings()` and used in `onNewIntent()`, `loadUrlFromTextBox()`, `initializeApp()`, and `initializeWebView()`.
     private String searchURL;
 
@@ -273,14 +271,15 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
     private int defaultProgressViewStartOffset;
     private int defaultProgressViewEndOffset;
 
-    // The URL sanitizers are set in `applyAppSettings()` and used in `sanitizeUrl()`.
-    private boolean sanitizeGoogleAnalytics;
-    private boolean sanitizeFacebookClickIds;
-    private boolean sanitizeTwitterAmpRedirects;
+    // Declare the helpers.
+    private BookmarksDatabaseHelper bookmarksDatabaseHelper;
+    private DomainsDatabaseHelper domainsDatabaseHelper;
+    private ProxyHelper proxyHelper;
+    private SanitizeUrlHelper sanitizeUrlHelper;
 
     // Declare the class variables
-    private BookmarksDatabaseHelper bookmarksDatabaseHelper;
     private boolean bottomAppBar;
+    private boolean displayAdditionalAppBarIcons;
     private boolean displayingFullScreenVideo;
     private boolean downloadWithExternalApp;
     private boolean fullScreenBrowsingModeEnabled;
@@ -289,9 +288,10 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
     private boolean inFullScreenBrowsingMode;
     private boolean loadingNewIntent;
     private BroadcastReceiver orbotStatusBroadcastReceiver;
-    private ProxyHelper proxyHelper;
     private boolean reapplyAppSettingsOnRestart;
     private boolean reapplyDomainSettingsOnRestart;
+    private boolean sanitizeAmpRedirects;
+    private boolean sanitizeTrackingQueries;
     private boolean scrollAppBar;
     private boolean waitingForProxy;
     private String webViewDefaultUserAgent;
@@ -370,7 +370,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
     private Activity resultLauncherActivityHandle;
 
     // Define the save URL activity result launcher.  It must be defined before `onCreate()` is run or the app will crash.
-    private final ActivityResultLauncher<String> saveUrlActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.CreateDocument(),
+    private final ActivityResultLauncher<String> saveUrlActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.CreateDocument("*/*"),
             new ActivityResultCallback<Uri>() {
                 @Override
                 public void onActivityResult(Uri fileUri) {
@@ -385,17 +385,36 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             });
 
     // Define the save webpage archive activity result launcher.  It must be defined before `onCreate()` is run or the app will crash.
-    private final ActivityResultLauncher<String> saveWebpageArchiveActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.CreateDocument(),
+    private final ActivityResultLauncher<String> saveWebpageArchiveActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.CreateDocument("multipart/related"),
             new ActivityResultCallback<Uri>() {
                 @Override
                 public void onActivityResult(Uri fileUri) {
                     // Only save the webpage archive if the file URI is not null, which happens if the user exited the file picker by pressing back.
                     if (fileUri != null) {
+                        // Initialize the file name string from the file URI last path segment.
+                        String temporaryFileNameString = fileUri.getLastPathSegment();
+
+                        // Query the exact file name if the API >= 26.
+                        if (Build.VERSION.SDK_INT >= 26) {
+                            // Get a cursor from the content resolver.
+                            Cursor contentResolverCursor = resultLauncherActivityHandle.getContentResolver().query(fileUri, null, null, null);
+
+                            // Move to the fist row.
+                            contentResolverCursor.moveToFirst();
+
+                            // Get the file name from the cursor.
+                            temporaryFileNameString = contentResolverCursor.getString(contentResolverCursor.getColumnIndexOrThrow(OpenableColumns.DISPLAY_NAME));
+
+                            // Close the cursor.
+                            contentResolverCursor.close();
+                        }
+
+                        // Save the final file name string so it can be used inside the lambdas.  This will no longer be needed once this activity has transitioned to Kotlin.
+                        String finalFileNameString = temporaryFileNameString;
+
                         try {
                             // Create a temporary MHT file.
                             File temporaryMhtFile = File.createTempFile("temporary_mht_file", ".mht", getCacheDir());
-
-                            // Save the temporary MHT file.
                             currentWebView.saveWebArchive(temporaryMhtFile.toString(), false, callbackValue -> {
                                 if (callbackValue != null) {  // The temporary MHT file was saved successfully.
                                     try {
@@ -420,29 +439,11 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                                         mhtOutputStream.close();
                                         temporaryMhtFileInputStream.close();
 
-                                        // Initialize the file name string from the file URI last path segment.
-                                        String fileNameString = fileUri.getLastPathSegment();
-
-                                        // Query the exact file name if the API >= 26.
-                                        if (Build.VERSION.SDK_INT >= 26) {
-                                            // Get a cursor from the content resolver.
-                                            Cursor contentResolverCursor = resultLauncherActivityHandle.getContentResolver().query(fileUri, null, null, null);
-
-                                            // Move to the fist row.
-                                            contentResolverCursor.moveToFirst();
-
-                                            // Get the file name from the cursor.
-                                            fileNameString = contentResolverCursor.getString(contentResolverCursor.getColumnIndexOrThrow(OpenableColumns.DISPLAY_NAME));
-
-                                            // Close the cursor.
-                                            contentResolverCursor.close();
-                                        }
-
                                         // Display a snackbar.
-                                        Snackbar.make(currentWebView, getString(R.string.file_saved) + "  " + fileNameString, Snackbar.LENGTH_SHORT).show();
+                                        Snackbar.make(currentWebView, getString(R.string.saved, finalFileNameString), Snackbar.LENGTH_SHORT).show();
                                     } catch (Exception exception) {
                                         // Display a snackbar with the exception.
-                                        Snackbar.make(currentWebView, getString(R.string.error_saving_file) + "  " + exception, Snackbar.LENGTH_INDEFINITE).show();
+                                        Snackbar.make(currentWebView, getString(R.string.error_saving_file, finalFileNameString, exception), Snackbar.LENGTH_INDEFINITE).show();
                                     } finally {
                                         // Delete the temporary MHT file.
                                         //noinspection ResultOfMethodCallIgnored
@@ -450,19 +451,19 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                                     }
                                 } else {  // There was an unspecified error while saving the temporary MHT file.
                                     // Display an error snackbar.
-                                    Snackbar.make(currentWebView, getString(R.string.error_saving_file), Snackbar.LENGTH_INDEFINITE).show();
+                                    Snackbar.make(currentWebView, getString(R.string.error_saving_file, finalFileNameString, getString(R.string.unknown_error)), Snackbar.LENGTH_INDEFINITE).show();
                                 }
                             });
                         } catch (IOException ioException) {
                             // Display a snackbar with the IO exception.
-                            Snackbar.make(currentWebView, getString(R.string.error_saving_file) + "  " + ioException, Snackbar.LENGTH_INDEFINITE).show();
+                            Snackbar.make(currentWebView, getString(R.string.error_saving_file, finalFileNameString, ioException), Snackbar.LENGTH_INDEFINITE).show();
                         }
                     }
                 }
             });
 
     // Define the save webpage image activity result launcher.  It must be defined before `onCreate()` is run or the app will crash.
-    private final ActivityResultLauncher<String> saveWebpageImageActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.CreateDocument(),
+    private final ActivityResultLauncher<String> saveWebpageImageActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.CreateDocument("image/png"),
             new ActivityResultCallback<Uri>() {
                 @Override
                 public void onActivityResult(Uri fileUri) {
@@ -500,9 +501,10 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
 
         // Get the preferences.
-        String appTheme = sharedPreferences.getString("app_theme", getString(R.string.app_theme_default_value));
+        String appTheme = sharedPreferences.getString(getString(R.string.app_theme_key), getString(R.string.app_theme_default_value));
         boolean allowScreenshots = sharedPreferences.getBoolean(getString(R.string.allow_screenshots_key), false);
         bottomAppBar = sharedPreferences.getBoolean(getString(R.string.bottom_app_bar_key), false);
+        displayAdditionalAppBarIcons = sharedPreferences.getBoolean(getString(R.string.display_additional_app_bar_icons_key), false);
 
         // Get the theme entry values string array.
         String[] appThemeEntryValuesStringArray = getResources().getStringArray(R.array.app_theme_entry_values);
@@ -532,15 +534,9 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Enable the drawing of the entire webpage.  This makes it possible to save a website image.  This must be done before anything else happens with the WebView.
         WebView.enableSlowWholeDocumentDraw();
 
-        // Set the theme.
-        setTheme(R.style.PrivacyBrowser);
-
-        // Set the content view.
-        if (bottomAppBar) {
-            setContentView(R.layout.main_framelayout_bottom_appbar);
-        } else {
-            setContentView(R.layout.main_framelayout_top_appbar);
-        }
+        // Set the content view according to the position of the app bar.
+        if (bottomAppBar) setContentView(R.layout.main_framelayout_bottom_appbar);
+        else setContentView(R.layout.main_framelayout_top_appbar);
 
         // Get handles for the views.
         rootFrameLayout = findViewById(R.id.root_framelayout);
@@ -594,6 +590,9 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Initially disable the sliding drawers.  They will be enabled once the blocklists are loaded.
         drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED);
 
+        // Initially hide the user interface so that only the blocklist loading screen is shown (if reloading).
+        drawerLayout.setVisibility(View.GONE);
+
         // Initialize the web view pager adapter.
         webViewPagerAdapter = new WebViewPagerAdapter(getSupportFragmentManager());
 
@@ -603,8 +602,11 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Store up to 100 tabs in memory.
         webViewPager.setOffscreenPageLimit(100);
 
-        // Instantiate the proxy helper.
+        // Instantiate the helpers.
+        bookmarksDatabaseHelper = new BookmarksDatabaseHelper(this);
+        domainsDatabaseHelper = new DomainsDatabaseHelper(this);
         proxyHelper = new ProxyHelper();
+        sanitizeUrlHelper = new SanitizeUrlHelper();
 
         // Initialize the app.
         initializeApp();
@@ -612,6 +614,48 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Apply the app settings from the shared preferences.
         applyAppSettings();
 
+        // Control what the system back command does.
+        OnBackPressedCallback onBackPressedCallback = new OnBackPressedCallback(true) {
+            @Override
+            public void handleOnBackPressed() {
+                // Process the different back options.
+                if (drawerLayout.isDrawerVisible(GravityCompat.START)) {  // The navigation drawer is open.
+                    // Close the navigation drawer.
+                    drawerLayout.closeDrawer(GravityCompat.START);
+                } else if (drawerLayout.isDrawerVisible(GravityCompat.END)){  // The bookmarks drawer is open.
+                    // close the bookmarks drawer.
+                    drawerLayout.closeDrawer(GravityCompat.END);
+                } else if (displayingFullScreenVideo) {  // A full screen video is shown.
+                    // Exit the full screen video.
+                    exitFullScreenVideo();
+                } else if (currentWebView.canGoBack()) {  // There is at least one item in the current WebView history.
+                    // Get the current web back forward list.
+                    WebBackForwardList webBackForwardList = currentWebView.copyBackForwardList();
+
+                    // Get the previous entry URL.
+                    String previousUrl = webBackForwardList.getItemAtIndex(webBackForwardList.getCurrentIndex() - 1).getUrl();
+
+                    // Apply the domain settings.
+                    applyDomainSettings(currentWebView, previousUrl, false, false, false);
+
+                    // Go back.
+                    currentWebView.goBack();
+                } else if (tabLayout.getTabCount() > 1) {  // There are at least two tabs.
+                    // Close the current tab.
+                    closeCurrentTab();
+                } else {  // There isn't anything to do in Privacy Browser.
+                    // Close Privacy Browser.  `finishAndRemoveTask()` also removes Privacy Browser from the recent app list.
+                    finishAndRemoveTask();
+
+                    // Manually kill Privacy Browser.  Otherwise, it is glitchy when restarted.
+                    System.exit(0);
+                }
+            }
+        };
+
+        // Register the on back pressed callback.
+        getOnBackPressedDispatcher().addCallback(this, onBackPressedCallback);
+
         // Populate the blocklists.
         populateBlocklists = new PopulateBlocklists(this, this).execute();
     }
@@ -621,9 +665,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Run the default commands.
         super.onNewIntent(intent);
 
-        // Replace the intent that started the app with this one.
-        setIntent(intent);
-
         // Check to see if the app is being restarted from a saved state.
         if (savedStateArrayList == null || savedStateArrayList.size() == 0) {  // The activity is not being restarted from a saved state.
             // Get the information from the intent.
@@ -674,7 +715,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 }
 
                 // Add a new tab if specified in the preferences.
-                if (sharedPreferences.getBoolean("open_intents_in_new_tab", true)) {  // Load the URL in a new tab.
+                if (sharedPreferences.getBoolean(getString(R.string.open_intents_in_new_tab_key), true)) {  // Load the URL in a new tab.
                     // Set the loading new intent flag.
                     loadingNewIntent = true;
 
@@ -695,6 +736,9 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     drawerLayout.closeDrawer(GravityCompat.END);
                 }
             }
+        } else {  // The app has been restarted.
+            // Replace the intent that started the app with this one.  This will load the tab after the others have been restored.
+            setIntent(intent);
         }
     }
 
@@ -978,12 +1022,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Disable the clear form data menu item if the API >= 26 so that the status of the main Clear Data is calculated correctly.
         optionsClearFormDataMenuItem.setEnabled(Build.VERSION.SDK_INT < 26);
 
-        // Get the shared preferences.
-        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
-
-        // Get the dark theme and app bar preferences.
-        boolean displayAdditionalAppBarIcons = sharedPreferences.getBoolean(getString(R.string.display_additional_app_bar_icons_key), false);
-
         // Set the status of the additional app bar icons.  Setting the refresh menu item to `SHOW_AS_ACTION_ALWAYS` makes it appear even on small devices like phones.
         if (displayAdditionalAppBarIcons) {
             optionsRefreshMenuItem.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
@@ -1061,8 +1099,17 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             // Enable DOM Storage if JavaScript is enabled.
             optionsDomStorageMenuItem.setEnabled(currentWebView.getSettings().getJavaScriptEnabled());
 
+            // Get the current theme status.
+            int currentThemeStatus = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
+
+            // Enable dark WebView if the API is < 33 or if night mode is enabled.
+            optionsDarkWebViewMenuItem.setEnabled((Build.VERSION.SDK_INT < 33) || (currentThemeStatus == Configuration.UI_MODE_NIGHT_YES));
+
             // Set the checkbox status for dark WebView if the WebView supports it.
-            if (WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {
+            if ((Build.VERSION.SDK_INT >= 33) && WebViewFeature.isFeatureSupported(WebViewFeature.ALGORITHMIC_DARKENING)) {  // The device is running API >= 33 and algorithmic darkening is supported.
+                optionsDarkWebViewMenuItem.setChecked(WebSettingsCompat.isAlgorithmicDarkeningAllowed(currentWebView.getSettings()));
+            } else if ((Build.VERSION.SDK_INT < 33) && WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {  // The device is running API < 33 and the WebView supports force dark.
+                //noinspection deprecation
                 optionsDarkWebViewMenuItem.setChecked(WebSettingsCompat.getForceDark(currentWebView.getSettings()) == WebSettingsCompat.FORCE_DARK_ON);
             }
         }
@@ -1688,7 +1735,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             return true;
         } else if (menuItemId == R.id.user_agent_custom) {  // User Agent - Custom.
             // Update the user agent.
-            currentWebView.getSettings().setUserAgentString(sharedPreferences.getString("custom_user_agent", getString(R.string.custom_user_agent_default_value)));
+            currentWebView.getSettings().setUserAgentString(sharedPreferences.getString(getString(R.string.custom_user_agent_key), getString(R.string.custom_user_agent_default_value)));
 
             // Reload the current WebView.
             currentWebView.reload();
@@ -1742,13 +1789,19 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             return true;
         } else if (menuItemId == R.id.dark_webview) {  // Dark WebView.
             // Check to see if dark WebView is supported by this WebView.
-            if (WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {
+            if ((Build.VERSION.SDK_INT >= 33) && WebViewFeature.isFeatureSupported(WebViewFeature.ALGORITHMIC_DARKENING)) {  // The device is running API >= 33 and algorithmic darkening is supported.
+                // Toggle algorithmic darkening.
+                WebSettingsCompat.setAlgorithmicDarkeningAllowed(currentWebView.getSettings(), !WebSettingsCompat.isAlgorithmicDarkeningAllowed(currentWebView.getSettings()));
+            } else if ((Build.VERSION.SDK_INT < 33) && WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {  // The device is running API < 33 and the WebView supports force dark.
                 // Toggle the dark WebView setting.
+                //noinspection deprecation
                 if (WebSettingsCompat.getForceDark(currentWebView.getSettings()) == WebSettingsCompat.FORCE_DARK_ON) {  // Dark WebView is currently enabled.
                     // Turn off dark WebView.
+                    //noinspection deprecation
                     WebSettingsCompat.setForceDark(currentWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
                 } else {  // Dark WebView is currently disabled.
                     // Turn on dark WebView.
+                    //noinspection deprecation
                     WebSettingsCompat.setForceDark(currentWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                 }
             }
@@ -1905,19 +1958,19 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             // Consume the event.
             return true;
         } else if (menuItemId == R.id.add_or_edit_domain) {  // Add or edit domain.
+            // Reapply the domain settings on returning to `MainWebViewActivity`.
+            reapplyDomainSettingsOnRestart = true;
+
             // Check if domain settings currently exist.
             if (currentWebView.getDomainSettingsApplied()) {  // Edit the current domain settings.
-                // Reapply the domain settings on returning to `MainWebViewActivity`.
-                reapplyDomainSettingsOnRestart = true;
-
                 // Create an intent to launch the domains activity.
                 Intent domainsIntent = new Intent(this, DomainsActivity.class);
 
                 // Add the extra information to the intent.
-                domainsIntent.putExtra("load_domain", currentWebView.getDomainSettingsDatabaseId());
-                domainsIntent.putExtra("close_on_back", true);
-                domainsIntent.putExtra("current_url", currentWebView.getUrl());
-                domainsIntent.putExtra("current_ip_addresses", currentWebView.getCurrentIpAddresses());
+                domainsIntent.putExtra(DomainsActivity.LOAD_DOMAIN, currentWebView.getDomainSettingsDatabaseId());
+                domainsIntent.putExtra(DomainsActivity.CLOSE_ON_BACK, true);
+                domainsIntent.putExtra(DomainsActivity.CURRENT_URL, currentWebView.getUrl());
+                domainsIntent.putExtra(DomainsActivity.CURRENT_IP_ADDRESSES, currentWebView.getCurrentIpAddresses());
 
                 // Get the current certificate.
                 SslCertificate sslCertificate = currentWebView.getCertificate();
@@ -1935,28 +1988,28 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     long endDateLong = sslCertificate.getValidNotAfterDate().getTime();
 
                     // Add the certificate to the intent.
-                    domainsIntent.putExtra("ssl_issued_to_cname", issuedToCName);
-                    domainsIntent.putExtra("ssl_issued_to_oname", issuedToOName);
-                    domainsIntent.putExtra("ssl_issued_to_uname", issuedToUName);
-                    domainsIntent.putExtra("ssl_issued_by_cname", issuedByCName);
-                    domainsIntent.putExtra("ssl_issued_by_oname", issuedByOName);
-                    domainsIntent.putExtra("ssl_issued_by_uname", issuedByUName);
-                    domainsIntent.putExtra("ssl_start_date", startDateLong);
-                    domainsIntent.putExtra("ssl_end_date", endDateLong);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_TO_CNAME, issuedToCName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_TO_ONAME, issuedToOName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_TO_UNAME, issuedToUName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_BY_CNAME, issuedByCName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_BY_ONAME, issuedByOName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_BY_UNAME, issuedByUName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_START_DATE, startDateLong);
+                    domainsIntent.putExtra(DomainsActivity.SSL_END_DATE, endDateLong);
                 }
 
                 // Make it so.
                 startActivity(domainsIntent);
             } else {  // Add a new domain.
-                // Apply the new domain settings on returning to `MainWebViewActivity`.
-                reapplyDomainSettingsOnRestart = true;
-
-                // Get the current domain
+                // Get the current URI.
                 Uri currentUri = Uri.parse(currentWebView.getUrl());
+
+                // Get the current domain from the URI.
                 String currentDomain = currentUri.getHost();
 
-                // Initialize the database handler.
-                DomainsDatabaseHelper domainsDatabaseHelper = new DomainsDatabaseHelper(this);
+                // Set an empty domain if it is null.
+                if (currentDomain == null)
+                    currentDomain = "";
 
                 // Create the domain and store the database ID.
                 int newDomainDatabaseId = domainsDatabaseHelper.addDomain(currentDomain);
@@ -1965,10 +2018,10 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 Intent domainsIntent = new Intent(this, DomainsActivity.class);
 
                 // Add the extra information to the intent.
-                domainsIntent.putExtra("load_domain", newDomainDatabaseId);
-                domainsIntent.putExtra("close_on_back", true);
-                domainsIntent.putExtra("current_url", currentWebView.getUrl());
-                domainsIntent.putExtra("current_ip_addresses", currentWebView.getCurrentIpAddresses());
+                domainsIntent.putExtra(DomainsActivity.LOAD_DOMAIN, newDomainDatabaseId);
+                domainsIntent.putExtra(DomainsActivity.CLOSE_ON_BACK, true);
+                domainsIntent.putExtra(DomainsActivity.CURRENT_URL, currentWebView.getUrl());
+                domainsIntent.putExtra(DomainsActivity.CURRENT_IP_ADDRESSES, currentWebView.getCurrentIpAddresses());
 
                 // Get the current certificate.
                 SslCertificate sslCertificate = currentWebView.getCertificate();
@@ -1986,14 +2039,14 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     long endDateLong = sslCertificate.getValidNotAfterDate().getTime();
 
                     // Add the certificate to the intent.
-                    domainsIntent.putExtra("ssl_issued_to_cname", issuedToCName);
-                    domainsIntent.putExtra("ssl_issued_to_oname", issuedToOName);
-                    domainsIntent.putExtra("ssl_issued_to_uname", issuedToUName);
-                    domainsIntent.putExtra("ssl_issued_by_cname", issuedByCName);
-                    domainsIntent.putExtra("ssl_issued_by_oname", issuedByOName);
-                    domainsIntent.putExtra("ssl_issued_by_uname", issuedByUName);
-                    domainsIntent.putExtra("ssl_start_date", startDateLong);
-                    domainsIntent.putExtra("ssl_end_date", endDateLong);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_TO_CNAME, issuedToCName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_TO_ONAME, issuedToOName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_TO_UNAME, issuedToUName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_BY_CNAME, issuedByCName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_BY_ONAME, issuedByOName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_ISSUED_BY_UNAME, issuedByUName);
+                    domainsIntent.putExtra(DomainsActivity.SSL_START_DATE, startDateLong);
+                    domainsIntent.putExtra(DomainsActivity.SSL_END_DATE, endDateLong);
                 }
 
                 // Make it so.
@@ -2131,8 +2184,8 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             Intent domainsIntent = new Intent(this, DomainsActivity.class);
 
             // Add the extra information to the intent.
-            domainsIntent.putExtra("current_url", currentWebView.getUrl());
-            domainsIntent.putExtra("current_ip_addresses", currentWebView.getCurrentIpAddresses());
+            domainsIntent.putExtra(DomainsActivity.CURRENT_URL, currentWebView.getUrl());
+            domainsIntent.putExtra(DomainsActivity.CURRENT_IP_ADDRESSES, currentWebView.getCurrentIpAddresses());
 
             // Get the current certificate.
             SslCertificate sslCertificate = currentWebView.getCertificate();
@@ -2184,6 +2237,15 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
             // Make it so.
             startActivity(logcatIntent);
+        } else if (menuItemId == R.id.webview_devtools) {  // WebView Dev.
+            // Create a WebView DevTools intent.
+            Intent webViewDevToolsIntent = new Intent("com.android.webview.SHOW_DEV_UI");
+
+            // Launch as a new task so that the WebView DevTools and Privacy Browser show as a separate windows in the recent tasks list.
+            webViewDevToolsIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+
+            // Make it so.
+            startActivity(webViewDevToolsIntent);
         } else if (menuItemId == R.id.guide) {  // Guide.
             // Create an intent to launch the guide activity.
             Intent guideIntent = new Intent(this, GuideActivity.class);
@@ -2663,7 +2725,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Update the bookmarks cursor with the current contents of this folder.
         bookmarksCursor = bookmarksDatabaseHelper.getBookmarksByDisplayOrder(currentBookmarksFolder);
 
-        // Update the `ListView`.
+        // Update the list view.
         bookmarksCursorAdapter.changeCursor(bookmarksCursor);
 
         // Scroll to the new folder.
@@ -2757,47 +2819,10 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Update the bookmarks cursor with the current contents of this folder.
         bookmarksCursor = bookmarksDatabaseHelper.getBookmarksByDisplayOrder(currentBookmarksFolder);
 
-        // Update the `ListView`.
+        // Update the list view.
         bookmarksCursorAdapter.changeCursor(bookmarksCursor);
     }
 
-    // Override `onBackPressed()` to handle the navigation drawer and and the WebViews.
-    @Override
-    public void onBackPressed() {
-        // Check the different options for processing `back`.
-        if (drawerLayout.isDrawerVisible(GravityCompat.START)) {  // The navigation drawer is open.
-            // Close the navigation drawer.
-            drawerLayout.closeDrawer(GravityCompat.START);
-        } else if (drawerLayout.isDrawerVisible(GravityCompat.END)){  // The bookmarks drawer is open.
-            // close the bookmarks drawer.
-            drawerLayout.closeDrawer(GravityCompat.END);
-        } else if (displayingFullScreenVideo) {  // A full screen video is shown.
-            // Exit the full screen video.
-            exitFullScreenVideo();
-        } else if (currentWebView.canGoBack()) {  // There is at least one item in the current WebView history.
-            // Get the current web back forward list.
-            WebBackForwardList webBackForwardList = currentWebView.copyBackForwardList();
-
-            // Get the previous entry URL.
-            String previousUrl = webBackForwardList.getItemAtIndex(webBackForwardList.getCurrentIndex() - 1).getUrl();
-
-            // Apply the domain settings.
-            applyDomainSettings(currentWebView, previousUrl, false, false, false);
-
-            // Go back.
-            currentWebView.goBack();
-        } else if (tabLayout.getTabCount() > 1) {  // There are at least two tabs.
-            // Close the current tab.
-            closeCurrentTab();
-        } else {  // There isn't anything to do in Privacy Browser.
-            // Close Privacy Browser.  `finishAndRemoveTask()` also removes Privacy Browser from the recent app list.
-            finishAndRemoveTask();
-
-            // Manually kill Privacy Browser.  Otherwise, it is glitchy when restarted.
-            System.exit(0);
-        }
-    }
-
     // Process the results of a file browse.
     @Override
     public void onActivityResult(int requestCode, int resultCode, Intent returnedIntent) {
@@ -3094,19 +3119,10 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         // Remove the lint warning below that the input method manager might be null.
         assert inputMethodManager != null;
 
-        // Initialize the gray foreground color spans for highlighting the URLs.
+        // Initialize the color spans for highlighting the URLs.
         initialGrayColorSpan = new ForegroundColorSpan(getColor(R.color.gray_500));
         finalGrayColorSpan = new ForegroundColorSpan(getColor(R.color.gray_500));
-
-        // Get the current theme status.
-        int currentThemeStatus = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
-
-        // Set the red color span according to the theme.
-        if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {
-            redColorSpan = new ForegroundColorSpan(getColor(R.color.red_a700));
-        } else {
-            redColorSpan = new ForegroundColorSpan(getColor(R.color.red_900));
-        }
+        redColorSpan = new ForegroundColorSpan(getColor(R.color.red_text));
 
         // Remove the formatting from the URL edit text when the user is editing the text.
         urlEditText.setOnFocusChangeListener((View v, boolean hasFocus) -> {
@@ -3385,15 +3401,10 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         drawerLayout.setDrawerTitle(GravityCompat.START, getString(R.string.navigation_drawer));
         drawerLayout.setDrawerTitle(GravityCompat.END, getString(R.string.bookmarks));
 
-        // Initialize the bookmarks database helper.
-        bookmarksDatabaseHelper = new BookmarksDatabaseHelper(this);
-
-        // Initialize `currentBookmarksFolder`.  `""` is the home folder in the database.
-        currentBookmarksFolder = "";
-
-        // Load the home folder, which is `""` in the database.
+        // Load the bookmarks folder.
         loadBookmarksFolder();
 
+        // Handle clicks on bookmarks.
         bookmarksListView.setOnItemClickListener((parent, view, position, id) -> {
             // Convert the id from long to int to match the format of the bookmarks database.
             int databaseId = (int) id;
@@ -3447,11 +3458,11 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 // Move the bookmark cursor to the first row.
                 bookmarkCursor.moveToFirst();
 
-                // Load the bookmark in a new tab but do not switch to the tab or close the drawer.
-                addNewTab(bookmarkCursor.getString(bookmarkCursor.getColumnIndexOrThrow(BookmarksDatabaseHelper.BOOKMARK_URL)), false);
+                // Load the bookmark in a new tab.
+                addNewTab(bookmarkCursor.getString(bookmarkCursor.getColumnIndexOrThrow(BookmarksDatabaseHelper.BOOKMARK_URL)), true);
 
-                // Display a snackbar.
-                Snackbar.make(currentWebView, R.string.bookmark_opened_in_background, Snackbar.LENGTH_SHORT).show();
+                // Close the bookmarks drawer.
+                drawerLayout.closeDrawer(GravityCompat.END);
             }
 
             // Consume the event.
@@ -3500,9 +3511,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             }
         });
 
-        // Replace the header that `WebView` creates for `X-Requested-With` with a null value.  The default value is the application ID (com.stoutner.privacybrowser.standard).
-        customHeaders.put("X-Requested-With", "");
-
         // Inflate a bare WebView to get the default user agent.  It is not used to render content on the screen.
         @SuppressLint("InflateParams") View webViewLayout = getLayoutInflater().inflate(R.layout.bare_webview, null, false);
 
@@ -3521,14 +3529,13 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
 
         // Store the values from the shared preferences in variables.
-        incognitoModeEnabled = sharedPreferences.getBoolean("incognito_mode", false);
-        sanitizeGoogleAnalytics = sharedPreferences.getBoolean("google_analytics", true);
-        sanitizeFacebookClickIds = sharedPreferences.getBoolean("facebook_click_ids", true);
-        sanitizeTwitterAmpRedirects = sharedPreferences.getBoolean("twitter_amp_redirects", true);
-        proxyMode = sharedPreferences.getString("proxy", getString(R.string.proxy_default_value));
-        fullScreenBrowsingModeEnabled = sharedPreferences.getBoolean("full_screen_browsing_mode", false);
+        incognitoModeEnabled = sharedPreferences.getBoolean(getString(R.string.incognito_mode_key), false);
+        sanitizeTrackingQueries = sharedPreferences.getBoolean(getString(R.string.tracking_queries_key), true);
+        sanitizeAmpRedirects = sharedPreferences.getBoolean(getString(R.string.amp_redirects_key), true);
+        proxyMode = sharedPreferences.getString(getString(R.string.proxy_key), getString(R.string.proxy_default_value));
+        fullScreenBrowsingModeEnabled = sharedPreferences.getBoolean(getString(R.string.full_screen_browsing_mode_key), false);
+        hideAppBar = sharedPreferences.getBoolean(getString(R.string.hide_app_bar_key), true);
         downloadWithExternalApp = sharedPreferences.getBoolean(getString(R.string.download_with_external_app_key), false);
-        hideAppBar = sharedPreferences.getBoolean("hide_app_bar", true);
         scrollAppBar = sharedPreferences.getBoolean(getString(R.string.scroll_app_bar_key), true);
 
         // Apply the saved proxy mode if the app has been restarted.
@@ -3541,20 +3548,37 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         }
 
         // Get the search string.
-        String searchString = sharedPreferences.getString("search", getString(R.string.search_default_value));
+        String searchString = sharedPreferences.getString(getString(R.string.search_key), getString(R.string.search_default_value));
 
         // Set the search string.
-        if (searchString.equals("Custom URL")) {  // A custom search string is used.
-            searchURL = sharedPreferences.getString("search_custom_url", getString(R.string.search_custom_url_default_value));
-        } else {  // A custom search string is not used.
+        if (searchString.equals(getString(R.string.custom_url_item)))
+            searchURL = sharedPreferences.getString(getString(R.string.search_custom_url_key), getString(R.string.search_custom_url_default_value));
+        else
             searchURL = searchString;
-        }
 
         // Apply the proxy.
         applyProxy(false);
 
-        // Adjust the layout and scrolling parameters if the app bar is at the top of the screen.
-        if (!bottomAppBar) {
+        // Adjust the layout and scrolling parameters according to the position of the app bar.
+        if (bottomAppBar) {  // The app bar is on the bottom.
+            // Adjust the UI.
+            if (scrollAppBar || (inFullScreenBrowsingMode && hideAppBar)) {  // The app bar scrolls or full screen browsing mode is engaged with the app bar hidden.
+                // Reset the WebView padding to fill the available space.
+                swipeRefreshLayout.setPadding(0, 0, 0, 0);
+            } else {  // The app bar doesn't scroll or full screen browsing mode is not engaged with the app bar hidden.
+                // Move the WebView above the app bar layout.
+                swipeRefreshLayout.setPadding(0, 0, 0, appBarHeight);
+
+                // Show the app bar if it is scrolled off the screen.
+                if (appBarLayout.getTranslationY() != 0) {
+                    // Animate the bottom app bar onto the screen.
+                    objectAnimator = ObjectAnimator.ofFloat(appBarLayout, "translationY", 0);
+
+                    // Make it so.
+                    objectAnimator.start();
+                }
+            }
+        } else {  // The app bar is on the top.
             // Get the current layout parameters.  Using coordinator layout parameters allows the `setBehavior()` command and using app bar layout parameters allows the `setScrollFlags()` command.
             CoordinatorLayout.LayoutParams swipeRefreshLayoutParams = (CoordinatorLayout.LayoutParams) swipeRefreshLayout.getLayoutParams();
             AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) toolbar.getLayoutParams();
@@ -3722,10 +3746,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 }
             }
 
-            // Initialize the database handler.
-            DomainsDatabaseHelper domainsDatabaseHelper = new DomainsDatabaseHelper(this);
-
-            // Get a full cursor from `domainsDatabaseHelper`.
+            // Get a full domain name cursor.
             Cursor domainNameCursor = domainsDatabaseHelper.getDomainNameCursorOrderedByDomain();
 
             // Initialize `domainSettingsSet`.
@@ -3780,12 +3801,12 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
 
             // Store the general preference information.
-            String defaultFontSizeString = sharedPreferences.getString("font_size", getString(R.string.font_size_default_value));
-            String defaultUserAgentName = sharedPreferences.getString("user_agent", getString(R.string.user_agent_default_value));
-            boolean defaultSwipeToRefresh = sharedPreferences.getBoolean("swipe_to_refresh", true);
-            String webViewTheme = sharedPreferences.getString("webview_theme", getString(R.string.webview_theme_default_value));
-            boolean wideViewport = sharedPreferences.getBoolean("wide_viewport", true);
-            boolean displayWebpageImages = sharedPreferences.getBoolean("display_webpage_images", true);
+            String defaultFontSizeString = sharedPreferences.getString(getString(R.string.font_size_key), getString(R.string.font_size_default_value));
+            String defaultUserAgentName = sharedPreferences.getString(getString(R.string.user_agent_key), getString(R.string.user_agent_default_value));
+            boolean defaultSwipeToRefresh = sharedPreferences.getBoolean(getString(R.string.swipe_to_refresh_key), true);
+            String webViewTheme = sharedPreferences.getString(getString(R.string.webview_theme_key), getString(R.string.webview_theme_default_value));
+            boolean wideViewport = sharedPreferences.getBoolean(getString(R.string.wide_viewport_key), true);
+            boolean displayWebpageImages = sharedPreferences.getBoolean(getString(R.string.display_webpage_images_key), true);
 
             // Get the WebView theme entry values string array.
             String[] webViewThemeEntryValuesStringArray = getResources().getStringArray(R.array.webview_theme_entry_values);
@@ -3816,12 +3837,14 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 boolean saveFormData = (currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.ENABLE_FORM_DATA)) == 1);
                 nestedScrollWebView.setEasyListEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.ENABLE_EASYLIST)) == 1);
                 nestedScrollWebView.setEasyPrivacyEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.ENABLE_EASYPRIVACY)) == 1);
-                nestedScrollWebView.setFanboysAnnoyanceListEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.ENABLE_FANBOYS_ANNOYANCE_LIST)) == 1);
+                nestedScrollWebView.setFanboysAnnoyanceListEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(
+                        DomainsDatabaseHelper.ENABLE_FANBOYS_ANNOYANCE_LIST)) == 1);
                 nestedScrollWebView.setFanboysSocialBlockingListEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(
                         DomainsDatabaseHelper.ENABLE_FANBOYS_SOCIAL_BLOCKING_LIST)) == 1);
                 nestedScrollWebView.setUltraListEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.ULTRALIST)) == 1);
                 nestedScrollWebView.setUltraPrivacyEnabled(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.ENABLE_ULTRAPRIVACY)) == 1);
-                nestedScrollWebView.setBlockAllThirdPartyRequests(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.BLOCK_ALL_THIRD_PARTY_REQUESTS)) == 1);
+                nestedScrollWebView.setBlockAllThirdPartyRequests(currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(
+                        DomainsDatabaseHelper.BLOCK_ALL_THIRD_PARTY_REQUESTS)) == 1);
                 String userAgentName = currentDomainSettingsCursor.getString(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.USER_AGENT));
                 int fontSize = currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.FONT_SIZE));
                 int swipeToRefreshInt = currentDomainSettingsCursor.getInt(currentDomainSettingsCursor.getColumnIndexOrThrow(DomainsDatabaseHelper.SWIPE_TO_REFRESH));
@@ -3894,7 +3917,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                         case SETTINGS_CUSTOM_USER_AGENT:
                             // Set the default custom user agent.
-                            nestedScrollWebView.getSettings().setUserAgentString(sharedPreferences.getString("custom_user_agent", getString(R.string.custom_user_agent_default_value)));
+                            nestedScrollWebView.getSettings().setUserAgentString(sharedPreferences.getString(getString(R.string.custom_user_agent_key), getString(R.string.custom_user_agent_default_value)));
                             break;
 
                         default:
@@ -3951,19 +3974,52 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                         // Disable swipe to refresh.
                         swipeRefreshLayout.setEnabled(false);
+                        break;
                 }
 
                 // Check to see if WebView themes are supported.
-                if (WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {
+                if ((Build.VERSION.SDK_INT >= 33) && WebViewFeature.isFeatureSupported(WebViewFeature.ALGORITHMIC_DARKENING)) {  // The device is running API >= 33 and algorithmic darkening is supported.
+                    // Set the WebView theme.
+                    switch (webViewThemeInt) {
+                        case DomainsDatabaseHelper.SYSTEM_DEFAULT:
+                            // Set the WebView theme.  A switch statement cannot be used because the WebView theme entry values string array is not a compile time constant.
+                            if (webViewTheme.equals(webViewThemeEntryValuesStringArray[1])) {  // The light theme is selected.
+                                // Turn off algorithmic darkening.
+                                WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), false);
+                            } else if (webViewTheme.equals(webViewThemeEntryValuesStringArray[2])) {  // The dark theme is selected.
+                                // Turn on algorithmic darkening.
+                                WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), true);
+                            } else {  // The system default theme is selected.
+                                // Get the current system theme status.
+                                int currentThemeStatus = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
+
+                                // Set the algorithmic darkening according to the current system theme status.
+                                WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), (currentThemeStatus == Configuration.UI_MODE_NIGHT_YES));
+                            }
+                            break;
+
+                        case DomainsDatabaseHelper.LIGHT_THEME:
+                            // Turn off algorithmic darkening.
+                            WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), false);
+                            break;
+
+                        case DomainsDatabaseHelper.DARK_THEME:
+                            // Turn on algorithmic darkening.
+                            WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), true);
+                            break;
+                    }
+                } else if ((Build.VERSION.SDK_INT < 33) && WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {  // The device is running API < 33 and the WebView supports force dark.
                     // Set the WebView theme.
                     switch (webViewThemeInt) {
                         case DomainsDatabaseHelper.SYSTEM_DEFAULT:
                             // Set the WebView theme.  A switch statement cannot be used because the WebView theme entry values string array is not a compile time constant.
                             if (webViewTheme.equals(webViewThemeEntryValuesStringArray[1])) {  // The light theme is selected.
                                 // Turn off the WebView dark mode.
+                                //noinspection deprecation
                                 WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
                             } else if (webViewTheme.equals(webViewThemeEntryValuesStringArray[2])) {  // The dark theme is selected.
                                 // Turn on the WebView dark mode.
+                                //noinspection deprecation
                                 WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                             } else {  // The system default theme is selected.
                                 // Get the current system theme status.
@@ -3972,9 +4028,11 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                                 // Set the WebView theme according to the current system theme status.
                                 if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {  // The system is in day mode.
                                     // Turn off the WebView dark mode.
+                                    //noinspection deprecation
                                     WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
                                 } else {  // The system is in night mode.
                                     // Turn on the WebView dark mode.
+                                    //noinspection deprecation
                                     WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                                 }
                             }
@@ -3982,11 +4040,13 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                         case DomainsDatabaseHelper.LIGHT_THEME:
                             // Turn off the WebView dark mode.
+                            //noinspection deprecation
                             WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
                             break;
 
                         case DomainsDatabaseHelper.DARK_THEME:
                             // Turn on the WebView dark mode.
+                            //noinspection deprecation
                             WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                             break;
                     }
@@ -4026,17 +4086,17 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 urlRelativeLayout.setBackground(ResourcesCompat.getDrawable(getResources(), R.drawable.domain_settings_url_background, null));
             } else {  // The new URL does not have custom domain settings.  Load the defaults.
                 // Store the values from the shared preferences.
-                nestedScrollWebView.getSettings().setJavaScriptEnabled(sharedPreferences.getBoolean("javascript", false));
+                nestedScrollWebView.getSettings().setJavaScriptEnabled(sharedPreferences.getBoolean(getString(R.string.javascript_key), false));
                 nestedScrollWebView.setAcceptCookies(sharedPreferences.getBoolean(getString(R.string.cookies_key), false));
-                nestedScrollWebView.getSettings().setDomStorageEnabled(sharedPreferences.getBoolean("dom_storage", false));
-                boolean saveFormData = sharedPreferences.getBoolean("save_form_data", false);  // Form data can be removed once the minimum API >= 26.
-                nestedScrollWebView.setEasyListEnabled(sharedPreferences.getBoolean("easylist", true));
-                nestedScrollWebView.setEasyPrivacyEnabled(sharedPreferences.getBoolean("easyprivacy", true));
-                nestedScrollWebView.setFanboysAnnoyanceListEnabled(sharedPreferences.getBoolean("fanboys_annoyance_list", true));
-                nestedScrollWebView.setFanboysSocialBlockingListEnabled(sharedPreferences.getBoolean("fanboys_social_blocking_list", true));
-                nestedScrollWebView.setUltraListEnabled(sharedPreferences.getBoolean("ultralist", true));
-                nestedScrollWebView.setUltraPrivacyEnabled(sharedPreferences.getBoolean("ultraprivacy", true));
-                nestedScrollWebView.setBlockAllThirdPartyRequests(sharedPreferences.getBoolean("block_all_third_party_requests", false));
+                nestedScrollWebView.getSettings().setDomStorageEnabled(sharedPreferences.getBoolean(getString(R.string.dom_storage_key), false));
+                boolean saveFormData = sharedPreferences.getBoolean(getString(R.string.save_form_data_key), false);  // Form data can be removed once the minimum API >= 26.
+                nestedScrollWebView.setEasyListEnabled(sharedPreferences.getBoolean(getString(R.string.easylist_key), true));
+                nestedScrollWebView.setEasyPrivacyEnabled(sharedPreferences.getBoolean(getString(R.string.easyprivacy_key), true));
+                nestedScrollWebView.setFanboysAnnoyanceListEnabled(sharedPreferences.getBoolean(getString(R.string.fanboys_annoyance_list_key), true));
+                nestedScrollWebView.setFanboysSocialBlockingListEnabled(sharedPreferences.getBoolean(getString(R.string.fanboys_social_blocking_list_key), true));
+                nestedScrollWebView.setUltraListEnabled(sharedPreferences.getBoolean(getString(R.string.ultralist_key), true));
+                nestedScrollWebView.setUltraPrivacyEnabled(sharedPreferences.getBoolean(getString(R.string.ultraprivacy_key), true));
+                nestedScrollWebView.setBlockAllThirdPartyRequests(sharedPreferences.getBoolean(getString(R.string.block_all_third_party_requests_key), false));
 
                 // Apply the default cookie setting.
                 cookieManager.setAcceptCookie(nestedScrollWebView.getAcceptCookies());
@@ -4087,7 +4147,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                     case SETTINGS_CUSTOM_USER_AGENT:
                         // Set the default custom user agent.
-                        nestedScrollWebView.getSettings().setUserAgentString(sharedPreferences.getString("custom_user_agent", getString(R.string.custom_user_agent_default_value)));
+                        nestedScrollWebView.getSettings().setUserAgentString(sharedPreferences.getString(getString(R.string.custom_user_agent_key), getString(R.string.custom_user_agent_default_value)));
                         break;
 
                     default:
@@ -4096,13 +4156,30 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 }
 
                 // Apply the WebView theme if supported by the installed WebView.
-                if (WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {
+                if ((Build.VERSION.SDK_INT >= 33) && WebViewFeature.isFeatureSupported(WebViewFeature.ALGORITHMIC_DARKENING)) {  // The device is running API >= 33 and algorithmic darkening is supported.
+                    // Set the WebView theme.  A switch statement cannot be used because the WebView theme entry values string array is not a compile time constant.
+                    if (webViewTheme.equals(webViewThemeEntryValuesStringArray[1])) {  // the light theme is selected.
+                        // Turn off algorithmic darkening.
+                        WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), false);
+                    } else if (webViewTheme.equals(webViewThemeEntryValuesStringArray[2])) {  // The dark theme is selected.
+                        // Turn on algorithmic darkening.
+                        WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), true);
+                    } else {  // The system default theme is selected.
+                        // Get the current system theme status.
+                        int currentThemeStatus = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
+
+                        // Set the algorithmic darkening according to the current system theme status.
+                        WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), currentThemeStatus == Configuration.UI_MODE_NIGHT_YES);
+                    }
+                } else if ((Build.VERSION.SDK_INT < 33) && WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {  // The device is running API < 33 and the WebView supports force dark.
                     // Set the WebView theme.  A switch statement cannot be used because the WebView theme entry values string array is not a compile time constant.
                     if (webViewTheme.equals(webViewThemeEntryValuesStringArray[1])) {  // The light theme is selected.
                         // Turn off the WebView dark mode.
+                        //noinspection deprecation
                         WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
                     } else if (webViewTheme.equals(webViewThemeEntryValuesStringArray[2])) {  // The dark theme is selected.
                         // Turn on the WebView dark mode.
+                        //noinspection deprecation
                         WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                     } else {  // The system default theme is selected.
                         // Get the current system theme status.
@@ -4111,9 +4188,11 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                         // Set the WebView theme according to the current system theme status.
                         if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {  // The system is in day mode.
                             // Turn off the WebView dark mode.
+                            //noinspection deprecation
                             WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
                         } else {  // The system is in night mode.
                             // Turn on the WebView dark mode.
+                            //noinspection deprecation
                             WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                         }
                     }
@@ -4143,7 +4222,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
         // Load the URL if directed.  This makes sure that the domain settings are properly loaded before the URL.  By using `loadUrl()`, instead of `loadUrlFromBase()`, the Referer header will never be sent.
         if (loadUrl) {
-            nestedScrollWebView.loadUrl(url, customHeaders);
+            nestedScrollWebView.loadUrl(url);
         }
     }
 
@@ -4234,27 +4313,31 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 } else {
                     appBarLayout.setBackgroundResource(R.color.dark_blue_30);
                 }
+                // Get the package manager.
+                PackageManager packageManager = getPackageManager();
 
                 // Check to see if I2P is installed.
                 try {
-                    // Get the package manager.
-                    PackageManager packageManager = getPackageManager();
-
-                    // Check to see if I2P is in the list.  This will throw an error and drop to the catch section if it isn't installed.
+                    // Check to see if the F-Droid flavor is installed.  This will throw an error and drop to the catch section if it isn't installed.
                     packageManager.getPackageInfo("net.i2p.android.router", 0);
-                } catch (PackageManager.NameNotFoundException exception) {  // I2P is not installed.
-                    // Sow the I2P not installed dialog if it is not already displayed.
-                    if (getSupportFragmentManager().findFragmentByTag(getString(R.string.proxy_not_installed_dialog)) == null) {
-                        // Get a handle for the waiting for proxy alert dialog.
-                        DialogFragment i2pNotInstalledDialogFragment = ProxyNotInstalledDialog.displayDialog(proxyMode);
+                } catch (PackageManager.NameNotFoundException fdroidException) {  // The F-Droid flavor is not installed.
+                    try {
+                        // Check to see if the Google Play flavor is installed.  This will throw an error and drop to the catch section if it isn't installed.
+                        packageManager.getPackageInfo("net.i2p.android", 0);
+                    } catch (PackageManager.NameNotFoundException googlePlayException) {  // The Google Play flavor is not installed.
+                        // Sow the I2P not installed dialog if it is not already displayed.
+                        if (getSupportFragmentManager().findFragmentByTag(getString(R.string.proxy_not_installed_dialog)) == null) {
+                            // Get a handle for the waiting for proxy alert dialog.
+                            DialogFragment i2pNotInstalledDialogFragment = ProxyNotInstalledDialog.displayDialog(proxyMode);
 
-                        // Try to show the dialog.  Sometimes the window is not yet active if returning from Settings.
-                        try {
-                            // Display the I2P not installed alert dialog.
-                            i2pNotInstalledDialogFragment.show(getSupportFragmentManager(), getString(R.string.proxy_not_installed_dialog));
-                        } catch (Exception i2pNotInstalledException) {
-                            // Add the dialog to the pending dialog array list.  It will be displayed in `onStart()`.
-                            pendingDialogsArrayList.add(new PendingDialog(i2pNotInstalledDialogFragment, getString(R.string.proxy_not_installed_dialog)));
+                            // Try to show the dialog.  Sometimes the window is not yet active if returning from Settings.
+                            try {
+                                // Display the I2P not installed alert dialog.
+                                i2pNotInstalledDialogFragment.show(getSupportFragmentManager(), getString(R.string.proxy_not_installed_dialog));
+                            } catch (Exception i2pNotInstalledException) {
+                                // Add the dialog to the pending dialog array list.  It will be displayed in `onStart()`.
+                                pendingDialogsArrayList.add(new PendingDialog(i2pNotInstalledDialogFragment, getString(R.string.proxy_not_installed_dialog)));
+                            }
                         }
                     }
                 }
@@ -4483,49 +4566,13 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
     }
 
     private String sanitizeUrl(String url) {
-        // Sanitize Google Analytics.
-        if (sanitizeGoogleAnalytics) {
-            // Remove `?utm_`.
-            if (url.contains("?utm_")) {
-                url = url.substring(0, url.indexOf("?utm_"));
-            }
-
-            // Remove `&utm_`.
-            if (url.contains("&utm_")) {
-                url = url.substring(0, url.indexOf("&utm_"));
-            }
-        }
-
-        // Sanitize Facebook Click IDs.
-        if (sanitizeFacebookClickIds) {
-            // Remove `?fbclid=`.
-            if (url.contains("?fbclid=")) {
-                url = url.substring(0, url.indexOf("?fbclid="));
-            }
-
-            // Remove `&fbclid=`.
-            if (url.contains("&fbclid=")) {
-                url = url.substring(0, url.indexOf("&fbclid="));
-            }
+        // Sanitize tracking queries.
+        if (sanitizeTrackingQueries)
+            url = sanitizeUrlHelper.sanitizeTrackingQueries(url);
 
-            // Remove `?fbadid=`.
-            if (url.contains("?fbadid=")) {
-                url = url.substring(0, url.indexOf("?fbadid="));
-            }
-
-            // Remove `&fbadid=`.
-            if (url.contains("&fbadid=")) {
-                url = url.substring(0, url.indexOf("&fbadid="));
-            }
-        }
-
-        // Sanitize Twitter AMP redirects.
-        if (sanitizeTwitterAmpRedirects) {
-            // Remove `?amp=1`.
-            if (url.contains("?amp=1")) {
-                url = url.substring(0, url.indexOf("?amp=1"));
-            }
-        }
+        // Sanitize AMP redirects.
+        if (sanitizeAmpRedirects)
+            url = sanitizeUrlHelper.sanitizeAmpRedirects(url);
 
         // Return the sanitized URL.
         return url;
@@ -4621,7 +4668,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 }
 
                 // Add a new tab if specified in the preferences.
-                if (sharedPreferences.getBoolean("open_intents_in_new_tab", true)) {  // Load the URL in a new tab.
+                if (sharedPreferences.getBoolean(getString(R.string.open_intents_in_new_tab_key), true)) {  // Load the URL in a new tab.
                     // Set the loading new intent flag.
                     loadingNewIntent = true;
 
@@ -4749,7 +4796,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         bookmarksDatabaseHelper.close();
 
         // Get the status of the clear everything preference.
-        boolean clearEverything = sharedPreferences.getBoolean("clear_everything", true);
+        boolean clearEverything = sharedPreferences.getBoolean(getString(R.string.clear_everything_key), true);
 
         // Get a handle for the runtime.
         Runtime runtime = Runtime.getRuntime();
@@ -4759,7 +4806,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         String privateDataDirectoryString = getApplicationInfo().dataDir;
 
         // Clear cookies.
-        if (clearEverything || sharedPreferences.getBoolean("clear_cookies", true)) {
+        if (clearEverything || sharedPreferences.getBoolean(getString(R.string.clear_cookies_key), true)) {
             // Request the cookies be deleted.
             CookieManager.getInstance().removeAllCookies(null);
 
@@ -4778,7 +4825,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         }
 
         // Clear DOM storage.
-        if (clearEverything || sharedPreferences.getBoolean("clear_dom_storage", true)) {
+        if (clearEverything || sharedPreferences.getBoolean(getString(R.string.clear_dom_storage_key), true)) {
             // Ask `WebStorage` to clear the DOM storage.
             WebStorage webStorage = WebStorage.getInstance();
             webStorage.deleteAllData();
@@ -4806,7 +4853,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         }
 
         // Clear form data if the API < 26.
-        if ((Build.VERSION.SDK_INT < 26) && (clearEverything || sharedPreferences.getBoolean("clear_form_data", true))) {
+        if ((Build.VERSION.SDK_INT < 26) && (clearEverything || sharedPreferences.getBoolean(getString(R.string.clear_form_data_key), true))) {
             WebViewDatabase webViewDatabase = WebViewDatabase.getInstance(this);
             webViewDatabase.clearFormData();
 
@@ -4838,7 +4885,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
         }
 
         // Clear the cache.
-        if (clearEverything || sharedPreferences.getBoolean("clear_cache", true)) {
+        if (clearEverything || sharedPreferences.getBoolean(getString(R.string.clear_cache_key), true)) {
             // Clear the cache from each WebView.
             for (int i = 0; i < webViewPagerAdapter.getCount(); i++) {
                 // Get the WebView tab fragment.
@@ -4864,7 +4911,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                 // Delete the secondary `Service Worker` cache directory.
                 // A string array must be used because the directory contains a space and `Runtime.exec` will otherwise not escape the string correctly.
-                Process deleteServiceWorkerProcess = runtime.exec(new String[] {"rm", "-rf", privateDataDirectoryString + "/app_webview/Service Worker/"});
+                Process deleteServiceWorkerProcess = runtime.exec(new String[] {"rm", "-rf", privateDataDirectoryString + "/app_webview/Default/Service Worker/"});
 
                 // Wait until the processes have finished.
                 deleteCacheProcess.waitFor();
@@ -4901,9 +4948,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             }
         }
 
-        // Clear the custom headers.
-        customHeaders.clear();
-
         // Manually delete the `app_webview` folder, which contains the cookies, DOM storage, form data, and `Service Worker` cache.
         // See `https://code.google.com/p/android/issues/detail?id=233826&thanks=233826&ts=1486670530`.
         if (clearEverything) {
@@ -5034,21 +5078,51 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
     @SuppressLint("ClickableViewAccessibility")
     @Override
-    public void initializeWebView(NestedScrollWebView nestedScrollWebView, int pageNumber, ProgressBar progressBar, String url, Boolean restoringState) {
+    public void initializeWebView(@NonNull NestedScrollWebView nestedScrollWebView, int pageNumber, @NonNull ProgressBar progressBar, @NonNull String url, boolean restoringState) {
         // Get a handle for the shared preferences.
         SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
 
         // Get the WebView theme.
-        String webViewTheme = sharedPreferences.getString("webview_theme", getString(R.string.webview_theme_default_value));
+        String webViewTheme = sharedPreferences.getString(getString(R.string.webview_theme_key), getString(R.string.webview_theme_default_value));
 
         // Get the WebView theme entry values string array.
         String[] webViewThemeEntryValuesStringArray = getResources().getStringArray(R.array.webview_theme_entry_values);
 
         // Apply the WebView theme if supported by the installed WebView.
-        if (WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {
+        if ((Build.VERSION.SDK_INT >= 33) && WebViewFeature.isFeatureSupported(WebViewFeature.ALGORITHMIC_DARKENING)) {  // The device is running API >= 33 and algorithmic darkening is supported.
+            // Set the WebView them.  A switch statement cannot be used because the WebView theme entry values string array is not a compile time constant.
+            if (webViewTheme.equals(webViewThemeEntryValuesStringArray[1])) {  // The light theme is selected.
+                // Turn off algorithmic darkening.
+                WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), false);
+
+                // Make the WebView visible. The WebView was created invisible in `webview_framelayout` to prevent a white background splash in night mode.
+                // If the system is currently in night mode, showing the WebView will be handled in `onProgressChanged()`.
+                nestedScrollWebView.setVisibility(View.VISIBLE);
+            } else if (webViewTheme.equals(webViewThemeEntryValuesStringArray[2])) {  // The dark theme is selected.
+                // Turn on algorithmic darkening.
+                WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), true);
+            } else {
+                // The system default theme is selected.
+                int currentThemeStatus = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
+
+                // Set the algorithmic darkening according to the current system theme status.
+                if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {  // The system is in day mode.
+                    // Turn off algorithmic darkening.
+                    WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), false);
+
+                    // Make the WebView visible. The WebView was created invisible in `webview_framelayout` to prevent a white background splash in night mode.
+                    // If the system is currently in night mode, showing the WebView will be handled in `onProgressChanged()`.
+                    nestedScrollWebView.setVisibility(View.VISIBLE);
+                } else {  // The system is in night mode.
+                    // Turn on algorithmic darkening.
+                    WebSettingsCompat.setAlgorithmicDarkeningAllowed(nestedScrollWebView.getSettings(), true);
+                }
+            }
+        } else if ((Build.VERSION.SDK_INT < 33) && WebViewFeature.isFeatureSupported(WebViewFeature.FORCE_DARK)) {  // The device is running API < 33 and the WebView supports force dark.
             // Set the WebView theme.  A switch statement cannot be used because the WebView theme entry values string array is not a compile time constant.
             if (webViewTheme.equals(webViewThemeEntryValuesStringArray[1])) {  // The light theme is selected.
                 // Turn off the WebView dark mode.
+                //noinspection deprecation
                 WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
 
                 // Make the WebView visible. The WebView was created invisible in `webview_framelayout` to prevent a white background splash in night mode.
@@ -5056,6 +5130,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 nestedScrollWebView.setVisibility(View.VISIBLE);
             } else if (webViewTheme.equals(webViewThemeEntryValuesStringArray[2])) {  // The dark theme is selected.
                 // Turn on the WebView dark mode.
+                //noinspection deprecation
                 WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
             } else {  // The system default theme is selected.
                 // Get the current system theme status.
@@ -5064,6 +5139,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 // Set the WebView theme according to the current system theme status.
                 if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {  // The system is in day mode.
                     // Turn off the WebView dark mode.
+                    //noinspection deprecation
                     WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_OFF);
 
                     // Make the WebView visible. The WebView was created invisible in `webview_framelayout` to prevent a white background splash in night mode.
@@ -5071,6 +5147,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     nestedScrollWebView.setVisibility(View.VISIBLE);
                 } else {  // The system is in night mode.
                     // Turn on the WebView dark mode.
+                    //noinspection deprecation
                     WebSettingsCompat.setForceDark(nestedScrollWebView.getSettings(), WebSettingsCompat.FORCE_DARK_ON);
                 }
             }
@@ -5121,7 +5198,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     // Toggle the full screen browsing mode.
                     if (inFullScreenBrowsingMode) {  // Switch to full screen mode.
                         // Hide the app bar if specified.
-                        if (hideAppBar) {
+                        if (hideAppBar) {  // The app bar is hidden.
                             // Close the find on page bar if it is visible.
                             closeFindOnPage(null);
 
@@ -5131,8 +5208,11 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                             // Hide the action bar.
                             actionBar.hide();
 
-                            // Set layout and scrolling parameters if the app bar is at the top of the screen.
-                            if (!bottomAppBar) {
+                            // Set layout and scrolling parameters according to the position of the app bar.
+                            if (bottomAppBar) {  // The app bar is at the bottom.
+                                // Reset the WebView padding to fill the available space.
+                                swipeRefreshLayout.setPadding(0, 0, 0, 0);
+                            } else {  // The app bar is at the top.
                                 // Check to see if the app bar is normally scrolled.
                                 if (scrollAppBar) {  // The app bar is scrolled when it is displayed.
                                     // Get the swipe refresh layout parameters.
@@ -5148,6 +5228,18 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                                     swipeRefreshLayout.setProgressViewOffset(false, -200, defaultProgressViewEndOffset);
                                 }
                             }
+                        } else {  // The app bar is not hidden.
+                            // Adjust the UI for the bottom app bar.
+                            if (bottomAppBar) {
+                                // Adjust the UI according to the scrolling of the app bar.
+                                if (scrollAppBar) {
+                                    // Reset the WebView padding to fill the available space.
+                                    swipeRefreshLayout.setPadding(0, 0, 0, 0);
+                                } else {
+                                    // Move the WebView above the app bar layout.
+                                    swipeRefreshLayout.setPadding(0, 0, 0, appBarHeight);
+                                }
+                            }
                         }
 
                         /* Hide the system bars.
@@ -5166,23 +5258,32 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                             // Show the action bar.
                             actionBar.show();
+                        }
 
-                            // Set layout and scrolling parameters if the app bar is at the top of the screen.
-                            if (!bottomAppBar) {
-                                // Check to see if the app bar is normally scrolled.
-                                if (scrollAppBar) {  // The app bar is scrolled when it is displayed.
-                                    // Get the swipe refresh layout parameters.
-                                    CoordinatorLayout.LayoutParams swipeRefreshLayoutParams = (CoordinatorLayout.LayoutParams) swipeRefreshLayout.getLayoutParams();
-
-                                    // Add the off-screen scrolling layout.
-                                    swipeRefreshLayoutParams.setBehavior(new AppBarLayout.ScrollingViewBehavior());
-                                } else {  // The app bar is not scrolled when it is displayed.
-                                    // The swipe refresh layout must be manually moved below the app bar layout.
-                                    swipeRefreshLayout.setPadding(0, appBarHeight, 0, 0);
-
-                                    // The swipe to refresh circle doesn't always hide itself completely unless it is moved up 10 pixels.
-                                    swipeRefreshLayout.setProgressViewOffset(false, defaultProgressViewStartOffset - 10 + appBarHeight, defaultProgressViewEndOffset + appBarHeight);
-                                }
+                        // Set layout and scrolling parameters according to the position of the app bar.
+                        if (bottomAppBar) {  // The app bar is at the bottom.
+                            // Adjust the UI.
+                            if (scrollAppBar) {
+                                // Reset the WebView padding to fill the available space.
+                                swipeRefreshLayout.setPadding(0, 0, 0, 0);
+                            } else {
+                                // Move the WebView above the app bar layout.
+                                swipeRefreshLayout.setPadding(0, 0, 0, appBarHeight);
+                            }
+                        } else {  // The app bar is at the top.
+                            // Check to see if the app bar is normally scrolled.
+                            if (scrollAppBar) {  // The app bar is scrolled when it is displayed.
+                                // Get the swipe refresh layout parameters.
+                                CoordinatorLayout.LayoutParams swipeRefreshLayoutParams = (CoordinatorLayout.LayoutParams) swipeRefreshLayout.getLayoutParams();
+
+                                // Add the off-screen scrolling layout.
+                                swipeRefreshLayoutParams.setBehavior(new AppBarLayout.ScrollingViewBehavior());
+                            } else {  // The app bar is not scrolled when it is displayed.
+                                // The swipe refresh layout must be manually moved below the app bar layout.
+                                swipeRefreshLayout.setPadding(0, appBarHeight, 0, 0);
+
+                                // The swipe to refresh circle doesn't always hide itself completely unless it is moved up 10 pixels.
+                                swipeRefreshLayout.setProgressViewOffset(false, defaultProgressViewStartOffset - 10 + appBarHeight, defaultProgressViewEndOffset + appBarHeight);
                             }
                         }
 
@@ -5196,6 +5297,30 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     return false;
                 }
             }
+
+            @Override
+            public boolean onFling(MotionEvent motionEvent1, MotionEvent motionEvent2, float velocityX, float velocityY) {
+                // Scroll the bottom app bar if enabled.
+                if (bottomAppBar && scrollAppBar && !objectAnimator.isRunning()) {
+                    // Calculate the Y change.
+                    float motionY = motionEvent2.getY() - motionEvent1.getY();
+
+                    // Scroll the app bar if the change is greater than 50 pixels.
+                    if (motionY > 50) {
+                        // Animate the bottom app bar onto the screen.
+                        objectAnimator = ObjectAnimator.ofFloat(appBarLayout, "translationY", 0);
+                    } else if (motionY < -50) {
+                        // Animate the bottom app bar off the screen.
+                        objectAnimator = ObjectAnimator.ofFloat(appBarLayout, "translationY", appBarLayout.getHeight());
+                    }
+
+                    // Make it so.
+                    objectAnimator.start();
+                }
+
+                // Do not consume the event.
+                return false;
+            }
         });
 
         // Pass all touch events on the WebView through the double-tap gesture detector.
@@ -5269,7 +5394,7 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             }
         });
 
-        // Update the status of swipe to refresh based on the scroll position of the nested scroll WebView.  Also reinforce full screen browsing mode.
+        // Process scroll changes.
         nestedScrollWebView.setOnScrollChangeListener((view, scrollX, scrollY, oldScrollX, oldScrollY) -> {
             // Set the swipe to refresh status.
             if (nestedScrollWebView.getSwipeToRefresh()) {
@@ -5280,23 +5405,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                 swipeRefreshLayout.setEnabled(false);
             }
 
-            //  Scroll the bottom app bar if enabled.
-            if (bottomAppBar && scrollAppBar && !objectAnimator.isRunning()) {
-                if (scrollY < oldScrollY) {  // The WebView was scrolled down.
-                    // Animate the bottom app bar onto the screen.
-                    objectAnimator = ObjectAnimator.ofFloat(appBarLayout, "translationY", 0);
-
-                    // Make it so.
-                    objectAnimator.start();
-                } else if (scrollY > oldScrollY) {  // The WebView was scrolled up.
-                    // Animate the bottom app bar off the screen.
-                    objectAnimator = ObjectAnimator.ofFloat(appBarLayout, "translationY", appBarLayout.getHeight());
-
-                    // Make it so.
-                    objectAnimator.start();
-                }
-            }
-
             // Reinforce the system UI visibility flags if in full screen browsing mode.
             // This hides the status and navigation bars, which are displayed if other elements are shown, like dialog boxes, the options menu, or the keyboard.
             if (inFullScreenBrowsingMode) {
@@ -5909,8 +6017,21 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
             @Override
             public void onPageStarted(WebView view, String url, Bitmap favicon) {
-                // Set the padding and layout settings if the app bar is at the top of the screen.
-                if (!bottomAppBar) {
+                // Get the app bar layout height.  This can't be done in `applyAppSettings()` because the app bar is not yet populated there.
+                // This should only be populated if it is greater than 0 because otherwise it will be reset to 0 if the app bar is hidden in full screen browsing mode.
+                if (appBarLayout.getHeight() > 0) appBarHeight = appBarLayout.getHeight();
+
+                // Set the padding and layout settings according to the position of the app bar.
+                if (bottomAppBar) {  // The app bar is on the bottom.
+                    // Adjust the UI.
+                    if (scrollAppBar || (inFullScreenBrowsingMode && hideAppBar)) {  // The app bar scrolls or full screen browsing mode is engaged with the app bar hidden.
+                        // Reset the WebView padding to fill the available space.
+                        swipeRefreshLayout.setPadding(0, 0, 0, 0);
+                    } else {  // The app bar doesn't scroll or full screen browsing mode is not engaged with the app bar hidden.
+                        // Move the WebView above the app bar layout.
+                        swipeRefreshLayout.setPadding(0, 0, 0, appBarHeight);
+                    }
+                } else {  // The app bar is on the top.
                     // Set the top padding of the swipe refresh layout according to the app bar scrolling preference.  This can't be done in `appAppSettings()` because the app bar is not yet populated there.
                     if (scrollAppBar || (inFullScreenBrowsingMode && hideAppBar)) {
                         // No padding is needed because it will automatically be placed below the app bar layout due to the scrolling layout behavior.
@@ -5919,9 +6040,6 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                         // The swipe to refresh circle doesn't always hide itself completely unless it is moved up 10 pixels.
                         swipeRefreshLayout.setProgressViewOffset(false, defaultProgressViewStartOffset - 10, defaultProgressViewEndOffset);
                     } else {
-                        // Get the app bar layout height.  This can't be done in `applyAppSettings()` because the app bar is not yet populated there.
-                        appBarHeight = appBarLayout.getHeight();
-
                         // The swipe refresh layout must be manually moved below the app bar layout.
                         swipeRefreshLayout.setPadding(0, appBarHeight, 0, 0);
 
@@ -5965,13 +6083,9 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     // Set the title.
                     optionsRefreshMenuItem.setTitle(R.string.stop);
 
-                    // Get the app bar and theme preferences.
-                    boolean displayAdditionalAppBarIcons = sharedPreferences.getBoolean(getString(R.string.display_additional_app_bar_icons_key), false);
-
-                    // Set the icon if it is displayed in the AppBar.  Once the minimum API is >= 26, the blue and black icons can be combined with a tint list.
-                    if (displayAdditionalAppBarIcons) {
+                    // Set the icon if it is displayed in the AppBar.
+                    if (displayAdditionalAppBarIcons)
                         optionsRefreshMenuItem.setIcon(R.drawable.close_blue);
-                    }
                 }
             }
 
@@ -5987,16 +6101,15 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     // Reset the Refresh title.
                     optionsRefreshMenuItem.setTitle(R.string.refresh);
 
-                    // Get the app bar and theme preferences.
-                    boolean displayAdditionalAppBarIcons = sharedPreferences.getBoolean(getString(R.string.display_additional_app_bar_icons_key), false);
-
-                    // If the icon is displayed in the app bar, reset it according to the theme.
-                    if (displayAdditionalAppBarIcons) {
-                        // Set the icon.
+                    // Reset the icon if it is displayed in the app bar.
+                    if (displayAdditionalAppBarIcons)
                         optionsRefreshMenuItem.setIcon(R.drawable.refresh_enabled);
-                    }
                 }
 
+                 // Get the application's private data directory, which will be something like `/data/user/0/com.stoutner.privacybrowser.standard`,
+                // which links to `/data/data/com.stoutner.privacybrowser.standard`.
+                String privateDataDirectoryString = getApplicationInfo().dataDir;
+
                 // Clear the cache, history, and logcat if Incognito Mode is enabled.
                 if (incognitoModeEnabled) {
                     // Clear the cache.  `true` includes disk files.
@@ -6007,16 +6120,8 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
 
                     // Manually delete cache folders.
                     try {
-                        // Get the application's private data directory, which will be something like `/data/user/0/com.stoutner.privacybrowser.standard`,
-                        // which links to `/data/data/com.stoutner.privacybrowser.standard`.
-                        String privateDataDirectoryString = getApplicationInfo().dataDir;
-
                         // Delete the main cache directory.
                         Runtime.getRuntime().exec("rm -rf " + privateDataDirectoryString + "/cache");
-
-                        // Delete the secondary `Service Worker` cache directory.
-                        // A `String[]` must be used because the directory contains a space and `Runtime.exec` will not escape the string correctly otherwise.
-                        Runtime.getRuntime().exec(new String[]{"rm", "-rf", privateDataDirectoryString + "/app_webview/Service Worker/"});
                     } catch (IOException exception) {
                         // Do nothing if an error is thrown.
                     }
@@ -6030,6 +6135,14 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
                     }
                 }
 
+                // Clear the `Service Worker` directory.
+                try {
+                    // A `String[]` must be used because the directory contains a space and `Runtime.exec` will not escape the string correctly otherwise.
+                    Runtime.getRuntime().exec(new String[]{"rm", "-rf", privateDataDirectoryString + "/app_webview/Default/Service Worker/"});
+                } catch (IOException exception) {
+                    // Do nothing.
+                }
+
                 // Get the current page position.
                 int currentPagePosition = webViewPagerAdapter.getPositionForId(nestedScrollWebView.getWebViewFragmentId());
 
@@ -6239,4 +6352,4 @@ public class MainWebViewActivity extends AppCompatActivity implements CreateBook
             }
         }
     }
-}
\ No newline at end of file
+}