app/src/main/java/com/stoutner/privacybrowser/fragments/AboutTabFragment.java

   1 /*
   2  * Copyright © 2016-2019 Soren Stoutner <soren@stoutner.com>.
   3  *
   4  * This file is part of Privacy Browser <https://www.stoutner.com/privacy-browser>.
   5  *
   6  * Privacy Browser is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * Privacy Browser is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with Privacy Browser.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 package com.stoutner.privacybrowser.fragments;
  21
  22 import android.annotation.SuppressLint;
  23 import android.content.Context;
  24 import android.content.pm.PackageManager;
  25 import android.content.pm.Signature;
  26 import android.os.Build;
  27 import android.os.Bundle;
  28 import android.text.SpannableStringBuilder;
  29 import android.text.Spanned;
  30 import android.text.style.ForegroundColorSpan;
  31 import android.view.LayoutInflater;
  32 import android.view.View;
  33 import android.view.ViewGroup;
  34 import android.webkit.WebView;
  35 import android.widget.TextView;
  36
  37 import androidx.annotation.NonNull;
  38 import androidx.fragment.app.Fragment;
  39
  40 import com.stoutner.privacybrowser.BuildConfig;
  41 import com.stoutner.privacybrowser.R;
  42 import com.stoutner.privacybrowser.activities.MainWebViewActivity;
  43
  44 import java.io.ByteArrayInputStream;
  45 import java.io.InputStream;
  46 import java.math.BigInteger;
  47 import java.security.Principal;
  48 import java.security.cert.CertificateException;
  49 import java.security.cert.CertificateFactory;
  50 import java.security.cert.X509Certificate;
  51 import java.text.DateFormat;
  52 import java.util.Date;
  53
  54 public class AboutTabFragment extends Fragment {
  55     // Track the current tab number.
  56     private int tabNumber;
  57
  58     // Store the tab number in the arguments bundle.
  59     public static AboutTabFragment createTab(int tab) {
  60         // Create a bundle.
  61         Bundle bundle = new Bundle();
  62
  63         // Store the tab number in the bundle.
  64         bundle.putInt("Tab", tab);
  65
  66         // Add the bundle to the fragment.
  67         AboutTabFragment aboutTabFragment = new AboutTabFragment();
  68         aboutTabFragment.setArguments(bundle);
  69
  70         // Return the new fragment.
  71         return aboutTabFragment;
  72     }
  73
  74     @Override
  75     public void onCreate(Bundle savedInstanceState) {
  76         // Run the default commands.
  77         super.onCreate(savedInstanceState);
  78
  79         // Remove the lint warning that `getArguments()` might be null.
  80         assert getArguments() != null;
  81
  82         // Store the tab number in a class variable.
  83         tabNumber = getArguments().getInt("Tab");
  84     }
  85
  86     @Override
  87     public View onCreateView(@NonNull LayoutInflater layoutInflater, ViewGroup container, Bundle savedInstanceState) {
  88         // Create a tab layout view.
  89         View tabLayout;
  90
  91         // Get a handle for the context and assert that it isn't null.
  92         Context context = getContext();
  93         assert context != null;
  94
  95         // Load the tabs.  Tab numbers start at 0.
  96         if (tabNumber == 0) {  // Load the about tab.
  97             // Setting false at the end of inflater.inflate does not attach the inflated layout as a child of container.  The fragment will take care of attaching the root automatically.
  98             tabLayout = layoutInflater.inflate(R.layout.about_tab_version, container, false);
  99
 100             // Get handles for the `TextViews`.
 101             TextView versionTextView = tabLayout.findViewById(R.id.version);
 102             TextView brandTextView = tabLayout.findViewById(R.id.brand);
 103             TextView manufacturerTextView = tabLayout.findViewById(R.id.manufacturer);
 104             TextView modelTextView = tabLayout.findViewById(R.id.model);
 105             TextView deviceTextView = tabLayout.findViewById(R.id.device);
 106             TextView bootloaderTextView = tabLayout.findViewById(R.id.bootloader);
 107             TextView radioTextView = tabLayout.findViewById(R.id.radio);
 108             TextView androidTextView = tabLayout.findViewById(R.id.android);
 109             TextView securityPatchTextView = tabLayout.findViewById(R.id.security_patch);
 110             TextView buildTextView = tabLayout.findViewById(R.id.build);
 111             TextView webViewTextView = tabLayout.findViewById(R.id.webview);
 112             TextView orbotTextView = tabLayout.findViewById(R.id.orbot);
 113             TextView openKeychainTextView = tabLayout.findViewById(R.id.open_keychain);
 114             TextView easyListTextView = tabLayout.findViewById(R.id.easylist);
 115             TextView easyPrivacyTextView = tabLayout.findViewById(R.id.easyprivacy);
 116             TextView fanboyAnnoyanceTextView = tabLayout.findViewById(R.id.fanboy_annoyance);
 117             TextView fanboySocialTextView = tabLayout.findViewById(R.id.fanboy_social);
 118             TextView ultraPrivacyTextView = tabLayout.findViewById(R.id.ultraprivacy);
 119             TextView certificateIssuerDNTextView = tabLayout.findViewById(R.id.certificate_issuer_dn);
 120             TextView certificateSubjectDNTextView = tabLayout.findViewById(R.id.certificate_subject_dn);
 121             TextView certificateStartDateTextView = tabLayout.findViewById(R.id.certificate_start_date);
 122             TextView certificateEndDateTextView = tabLayout.findViewById(R.id.certificate_end_date);
 123             TextView certificateVersionTextView = tabLayout.findViewById(R.id.certificate_version);
 124             TextView certificateSerialNumberTextView = tabLayout.findViewById(R.id.certificate_serial_number);
 125             TextView certificateSignatureAlgorithmTextView = tabLayout.findViewById(R.id.certificate_signature_algorithm);
 126
 127             // Setup the labels.
 128             String version = getString(R.string.version) + " " + BuildConfig.VERSION_NAME + " (" + getString(R.string.version_code) + " " + Integer.toString(BuildConfig.VERSION_CODE) + ")";
 129             String brandLabel = getString(R.string.brand) + "  ";
 130             String manufacturerLabel = getString(R.string.manufacturer) + "  ";
 131             String modelLabel = getString(R.string.model) + "  ";
 132             String deviceLabel = getString(R.string.device) + "  ";
 133             String bootloaderLabel = getString(R.string.bootloader) + "  ";
 134             String androidLabel = getString(R.string.android) + "  ";
 135             String buildLabel = getString(R.string.build) + "  ";
 136             String webViewLabel = getString(R.string.webview) + "  ";
 137             String easyListLabel = getString(R.string.easylist_label) + "  ";
 138             String easyPrivacyLabel = getString(R.string.easyprivacy_label) + "  ";
 139             String fanboyAnnoyanceLabel = getString(R.string.fanboy_annoyance_label) + "  ";
 140             String fanboySocialLabel = getString(R.string.fanboy_social_label) + "  ";
 141             String ultraPrivacyLabel = getString(R.string.ultraprivacy_label) + "  ";
 142             String issuerDNLabel = getString(R.string.issuer_dn) + "  ";
 143             String subjectDNLabel = getString(R.string.subject_dn) + "  ";
 144             String startDateLabel = getString(R.string.start_date) + "  ";
 145             String endDateLabel = getString(R.string.end_date) + "  ";
 146             String certificateVersionLabel = getString(R.string.certificate_version) + "  ";
 147             String serialNumberLabel = getString(R.string.serial_number) + "  ";
 148             String signatureAlgorithmLabel = getString(R.string.signature_algorithm) + "  ";
 149
 150             // `webViewLayout` is only used to get the default user agent from `bare_webview`.  It is not used to render content on the screen.
 151             View webViewLayout = layoutInflater.inflate(R.layout.bare_webview, container, false);
 152             WebView tabLayoutWebView = webViewLayout.findViewById(R.id.bare_webview);
 153             String userAgentString =  tabLayoutWebView.getSettings().getUserAgentString();
 154
 155             // Get the device's information and store it in strings.
 156             String brand = Build.BRAND;
 157             String manufacturer = Build.MANUFACTURER;
 158             String model = Build.MODEL;
 159             String device = Build.DEVICE;
 160             String bootloader = Build.BOOTLOADER;
 161             String radio = Build.getRadioVersion();
 162             String android = Build.VERSION.RELEASE + " (" + getString(R.string.api) + " " + Integer.toString(Build.VERSION.SDK_INT) + ")";
 163             String build = Build.DISPLAY;
 164             // Select the substring that begins after `Chrome/` and goes until the next ` `.
 165             String webView = userAgentString.substring(userAgentString.indexOf("Chrome/") + 7, userAgentString.indexOf(" ", userAgentString.indexOf("Chrome/")));
 166
 167             // Get the Orbot version name if Orbot is installed.
 168             String orbot;
 169             try {
 170                 // Store the version name.
 171                 orbot = context.getPackageManager().getPackageInfo("org.torproject.android", 0).versionName;
 172             } catch (PackageManager.NameNotFoundException exception) {  // Orbot is not installed.
 173                 orbot = "";
 174             }
 175
 176             // Get the OpenKeychain version name if it is installed.
 177             String openKeychain;
 178             try {
 179                 // Store the version name.
 180                 openKeychain = context.getPackageManager().getPackageInfo("org.sufficientlysecure.keychain", 0).versionName;
 181             } catch (PackageManager.NameNotFoundException exception) {  // OpenKeychain is not installed.
 182                 openKeychain = "";
 183             }
 184
 185             // Create a `SpannableStringBuilder` for the hardware and software `TextViews` that needs multiple colors of text.
 186             SpannableStringBuilder brandStringBuilder = new SpannableStringBuilder(brandLabel + brand);
 187             SpannableStringBuilder manufacturerStringBuilder = new SpannableStringBuilder(manufacturerLabel + manufacturer);
 188             SpannableStringBuilder modelStringBuilder = new SpannableStringBuilder(modelLabel + model);
 189             SpannableStringBuilder deviceStringBuilder = new SpannableStringBuilder(deviceLabel + device);
 190             SpannableStringBuilder bootloaderStringBuilder = new SpannableStringBuilder(bootloaderLabel + bootloader);
 191             SpannableStringBuilder androidStringBuilder = new SpannableStringBuilder(androidLabel + android);
 192             SpannableStringBuilder buildStringBuilder = new SpannableStringBuilder(buildLabel + build);
 193             SpannableStringBuilder webViewStringBuilder = new SpannableStringBuilder(webViewLabel + webView);
 194             SpannableStringBuilder easyListStringBuilder = new SpannableStringBuilder(easyListLabel + MainWebViewActivity.easyListVersion);
 195             SpannableStringBuilder easyPrivacyStringBuilder = new SpannableStringBuilder(easyPrivacyLabel + MainWebViewActivity.easyPrivacyVersion);
 196             SpannableStringBuilder fanboyAnnoyanceStringBuilder = new SpannableStringBuilder(fanboyAnnoyanceLabel + MainWebViewActivity.fanboysAnnoyanceVersion);
 197             SpannableStringBuilder fanboySocialStringBuilder = new SpannableStringBuilder(fanboySocialLabel + MainWebViewActivity.fanboysSocialVersion);
 198             SpannableStringBuilder ultraPrivacyStringBuilder = new SpannableStringBuilder(ultraPrivacyLabel + MainWebViewActivity.ultraPrivacyVersion);
 199
 200             // Create the `blueColorSpan` variable.
 201             ForegroundColorSpan blueColorSpan;
 202
 203             // Set `blueColorSpan` according to the theme.  We have to use the deprecated `getColor()` until API >= 23.
 204             if (MainWebViewActivity.darkTheme) {
 205                 //noinspection deprecation
 206                 blueColorSpan = new ForegroundColorSpan(getResources().getColor(R.color.blue_400));
 207             } else {
 208                 //noinspection deprecation
 209                 blueColorSpan = new ForegroundColorSpan(getResources().getColor(R.color.blue_700));
 210             }
 211
 212             // Setup the spans to display the device information in blue.  `SPAN_INCLUSIVE_INCLUSIVE` allows the span to grow in either direction.
 213             brandStringBuilder.setSpan(blueColorSpan, brandLabel.length(), brandStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 214             manufacturerStringBuilder.setSpan(blueColorSpan, manufacturerLabel.length(), manufacturerStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 215             modelStringBuilder.setSpan(blueColorSpan, modelLabel.length(), modelStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 216             deviceStringBuilder.setSpan(blueColorSpan, deviceLabel.length(), deviceStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 217             bootloaderStringBuilder.setSpan(blueColorSpan, bootloaderLabel.length(), bootloaderStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 218             androidStringBuilder.setSpan(blueColorSpan, androidLabel.length(), androidStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 219             buildStringBuilder.setSpan(blueColorSpan, buildLabel.length(), buildStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 220             webViewStringBuilder.setSpan(blueColorSpan, webViewLabel.length(), webViewStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 221             easyListStringBuilder.setSpan(blueColorSpan, easyListLabel.length(), easyListStringBuilder.length(), Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
 222             easyPrivacyStringBuilder.setSpan(blueColorSpan, easyPrivacyLabel.length(), easyPrivacyStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 223             fanboyAnnoyanceStringBuilder.setSpan(blueColorSpan, fanboyAnnoyanceLabel.length(), fanboyAnnoyanceStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 224             fanboySocialStringBuilder.setSpan(blueColorSpan, fanboySocialLabel.length(), fanboySocialStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 225             ultraPrivacyStringBuilder.setSpan(blueColorSpan, ultraPrivacyLabel.length(), ultraPrivacyStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 226
 227             // Display the strings in the text boxes.
 228             versionTextView.setText(version);
 229             brandTextView.setText(brandStringBuilder);
 230             manufacturerTextView.setText(manufacturerStringBuilder);
 231             modelTextView.setText(modelStringBuilder);
 232             deviceTextView.setText(deviceStringBuilder);
 233             bootloaderTextView.setText(bootloaderStringBuilder);
 234             androidTextView.setText(androidStringBuilder);
 235             buildTextView.setText(buildStringBuilder);
 236             webViewTextView.setText(webViewStringBuilder);
 237             easyListTextView.setText(easyListStringBuilder);
 238             easyPrivacyTextView.setText(easyPrivacyStringBuilder);
 239             fanboyAnnoyanceTextView.setText(fanboyAnnoyanceStringBuilder);
 240             fanboySocialTextView.setText(fanboySocialStringBuilder);
 241             ultraPrivacyTextView.setText(ultraPrivacyStringBuilder);
 242
 243             // Build.VERSION.SECURITY_PATCH is only available for SDK_INT >= 23.
 244             if (Build.VERSION.SDK_INT >= 23) {
 245                 String securityPatchLabel = getString(R.string.security_patch) + "  ";
 246                 String securityPatch = Build.VERSION.SECURITY_PATCH;
 247                 SpannableStringBuilder securityPatchStringBuilder = new SpannableStringBuilder(securityPatchLabel + securityPatch);
 248                 securityPatchStringBuilder.setSpan(blueColorSpan, securityPatchLabel.length(), securityPatchStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 249                 securityPatchTextView.setText(securityPatchStringBuilder);
 250             } else {  // SDK_INT < 23.
 251                 securityPatchTextView.setVisibility(View.GONE);
 252             }
 253
 254             // Only populate the radio text view if there is a radio in the device.
 255             if (!radio.isEmpty()) {
 256                 String radioLabel = getString(R.string.radio) + "  ";
 257                 SpannableStringBuilder radioStringBuilder = new SpannableStringBuilder(radioLabel + radio);
 258                 radioStringBuilder.setSpan(blueColorSpan, radioLabel.length(), radioStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 259                 radioTextView.setText(radioStringBuilder);
 260             } else {  // This device does not have a radio.
 261                 radioTextView.setVisibility(View.GONE);
 262             }
 263
 264             // Only populate the Orbot text view if it is installed.
 265             if (!orbot.isEmpty()) {
 266                 String orbotLabel = getString(R.string.orbot) + "  ";
 267                 SpannableStringBuilder orbotStringBuilder = new SpannableStringBuilder(orbotLabel + orbot);
 268                 orbotStringBuilder.setSpan(blueColorSpan, orbotLabel.length(), orbotStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 269                 orbotTextView.setText(orbotStringBuilder);
 270             } else {  // Orbot is not installed.
 271                 orbotTextView.setVisibility(View.GONE);
 272             }
 273
 274             // Only populate the OpenKeychain text view if it is installed.
 275             if (!openKeychain.isEmpty()) {
 276                 String openKeychainLabel = getString(R.string.openkeychain) + "  ";
 277                 SpannableStringBuilder openKeychainStringBuilder = new SpannableStringBuilder(openKeychainLabel + openKeychain);
 278                 openKeychainStringBuilder.setSpan(blueColorSpan, openKeychainLabel.length(), openKeychainStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 279                 openKeychainTextView.setText(openKeychainStringBuilder);
 280             } else {  //OpenKeychain is not installed.
 281                 openKeychainTextView.setVisibility(View.GONE);
 282             }
 283
 284             // Display the package signature.
 285             try {
 286                 // Get the first package signature.  Suppress the lint warning about the need to be careful in implementing comparison of certificates for security purposes.
 287                 @SuppressLint("PackageManagerGetSignatures") Signature packageSignature = getContext().getPackageManager().getPackageInfo(getContext().getPackageName(), PackageManager.GET_SIGNATURES).signatures[0];
 288
 289                 // Convert the signature to a `byte[]` `InputStream`.
 290                 InputStream certificateByteArrayInputStream = new ByteArrayInputStream(packageSignature.toByteArray());
 291
 292                 // Display the certificate information on the screen.
 293                 try {
 294                     // Instantiate a `CertificateFactory`.
 295                     CertificateFactory certificateFactory = CertificateFactory.getInstance("X509");
 296
 297                     // Generate an `X509Certificate`.
 298                     X509Certificate x509Certificate = (X509Certificate) certificateFactory.generateCertificate(certificateByteArrayInputStream);
 299
 300                     // Store the individual sections of the certificate that we are interested in.
 301                     Principal issuerDNPrincipal = x509Certificate.getIssuerDN();
 302                     Principal subjectDNPrincipal = x509Certificate.getSubjectDN();
 303                     Date startDate = x509Certificate.getNotBefore();
 304                     Date endDate = x509Certificate.getNotAfter();
 305                     int certificateVersion = x509Certificate.getVersion();
 306                     BigInteger serialNumberBigInteger = x509Certificate.getSerialNumber();
 307                     String signatureAlgorithmNameString = x509Certificate.getSigAlgName();
 308
 309                     // Create a `SpannableStringBuilder` for each `TextView` that needs multiple colors of text.
 310                     SpannableStringBuilder issuerDNStringBuilder = new SpannableStringBuilder(issuerDNLabel + issuerDNPrincipal.toString());
 311                     SpannableStringBuilder subjectDNStringBuilder = new SpannableStringBuilder(subjectDNLabel + subjectDNPrincipal.toString());
 312                     SpannableStringBuilder startDateStringBuilder = new SpannableStringBuilder(startDateLabel + DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.LONG).format(startDate));
 313                     SpannableStringBuilder endDataStringBuilder = new SpannableStringBuilder(endDateLabel + DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.LONG).format(endDate));
 314                     SpannableStringBuilder certificateVersionStringBuilder = new SpannableStringBuilder(certificateVersionLabel + certificateVersion);
 315                     SpannableStringBuilder serialNumberStringBuilder = new SpannableStringBuilder(serialNumberLabel + serialNumberBigInteger);
 316                     SpannableStringBuilder signatureAlgorithmStringBuilder = new SpannableStringBuilder(signatureAlgorithmLabel + signatureAlgorithmNameString);
 317
 318                     // Setup the spans to display the device information in blue.  `SPAN_INCLUSIVE_INCLUSIVE` allows the span to grow in either direction.
 319                     issuerDNStringBuilder.setSpan(blueColorSpan, issuerDNLabel.length(), issuerDNStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 320                     subjectDNStringBuilder.setSpan(blueColorSpan, subjectDNLabel.length(), subjectDNStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 321                     startDateStringBuilder.setSpan(blueColorSpan, startDateLabel.length(), startDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 322                     endDataStringBuilder.setSpan(blueColorSpan, endDateLabel.length(), endDataStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 323                     certificateVersionStringBuilder.setSpan(blueColorSpan, certificateVersionLabel.length(), certificateVersionStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 324                     serialNumberStringBuilder.setSpan(blueColorSpan, serialNumberLabel.length(), serialNumberStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 325                     signatureAlgorithmStringBuilder.setSpan(blueColorSpan, signatureAlgorithmLabel.length(), signatureAlgorithmStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 326
 327                     // Display the strings in the text boxes.
 328                     certificateIssuerDNTextView.setText(issuerDNStringBuilder);
 329                     certificateSubjectDNTextView.setText(subjectDNStringBuilder);
 330                     certificateStartDateTextView.setText(startDateStringBuilder);
 331                     certificateEndDateTextView.setText(endDataStringBuilder);
 332                     certificateVersionTextView.setText(certificateVersionStringBuilder);
 333                     certificateSerialNumberTextView.setText(serialNumberStringBuilder);
 334                     certificateSignatureAlgorithmTextView.setText(signatureAlgorithmStringBuilder);
 335                 } catch (CertificateException e) {
 336                     // Do nothing if there is a certificate error.
 337                 }
 338             } catch (PackageManager.NameNotFoundException e) {
 339                 // Do nothing if `PackageManager` says Privacy Browser isn't installed.
 340             }
 341         } else { // load a `WebView` for all the other tabs.  Tab numbers start at 0.
 342             // Setting false at the end of inflater.inflate does not attach the inflated layout as a child of container.  The fragment will take care of attaching the root automatically.
 343             tabLayout = layoutInflater.inflate(R.layout.bare_webview, container, false);
 344
 345             // Get a handle for `tabWebView`.
 346             WebView tabWebView = (WebView) tabLayout;
 347
 348             // Load the tabs according to the theme.
 349             if (MainWebViewActivity.darkTheme) {  // The dark theme is applied.
 350                 // Set the background color.  The deprecated `.getColor()` must be used until the minimum API >= 23.
 351                 //noinspection deprecation
 352                 tabWebView.setBackgroundColor(getResources().getColor(R.color.gray_850));
 353
 354                 switch (tabNumber) {
 355                     case 1:
 356                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_permissions_dark.html");
 357                         break;
 358
 359                     case 2:
 360                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_privacy_policy_dark.html");
 361                         break;
 362
 363                     case 3:
 364                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_changelog_dark.html");
 365                         break;
 366
 367                     case 4:
 368                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_licenses_dark.html");
 369                         break;
 370
 371                     case 5:
 372                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_contributors_dark.html");
 373                         break;
 374
 375                     case 6:
 376                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_links_dark.html");
 377                         break;
 378                 }
 379             } else {  // The light theme is applied.
 380                 switch (tabNumber) {
 381                     case 1:
 382                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_permissions_light.html");
 383                         break;
 384
 385                     case 2:
 386                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_privacy_policy_light.html");
 387                         break;
 388
 389                     case 3:
 390                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_changelog_light.html");
 391                         break;
 392
 393                     case 4:
 394                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_licenses_light.html");
 395                         break;
 396
 397                     case 5:
 398                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_contributors_light.html");
 399                         break;
 400
 401                     case 6:
 402                         tabWebView.loadUrl("file:///android_asset/" + getString(R.string.android_asset_path) + "/about_links_light.html");
 403                         break;
 404                 }
 405             }
 406         }
 407
 408         // Return the formatted `tabLayout`.
 409         return tabLayout;
 410     }
 411 }