Move majority of hardcoded consts to separate file

app/src/main/java/org/kiwix/kiwixmobile/KiwixMobileActivity.java

@@ -116,58 +116,48 @@ import okhttp3.OkHttpClient;
 import static android.content.res.Configuration.ORIENTATION_LANDSCAPE;
 import static org.kiwix.kiwixmobile.TableDrawerAdapter.DocumentSection;
 import static org.kiwix.kiwixmobile.TableDrawerAdapter.TableClickListener;
+import static org.kiwix.kiwixmobile.utils.Constants.BOOKMARK_CHOSEN_REQUEST;
+import static org.kiwix.kiwixmobile.utils.Constants.CONTACT_EMAIL_ADDRESS;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_BOOKMARK_CLICKED;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_BOOKMARK_CONTENTS;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_CHOSE_X_TITLE;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_CHOSE_X_URL;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_EXTERNAL_LINK;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_IS_WIDGET_SEARCH;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_IS_WIDGET_STAR;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_IS_WIDGET_VOICE;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_LIBRARY;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_NOTIFICATION_ID;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_SEARCH;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_ZIM_FILE;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_ZIM_FILE_2;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_BACK_TO_TOP;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_BOTTOM_TOOLBAR;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_EXTERNAL_LINK_POPUP;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_FULLSCREEN;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_HIDE_TOOLBAR;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_KIWIX_MOBILE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_LANG;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_NEW_TAB_BACKGROUND;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_WIFI_ONLY;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_ZOOM;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_ZOOM_ENABLED;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_FILE_SEARCH;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_FILE_SELECT;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_PREFERENCES;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_STORAGE_PERMISSION;
+import static org.kiwix.kiwixmobile.utils.Constants.RESULT_HISTORY_CLEARED;
+import static org.kiwix.kiwixmobile.utils.Constants.RESULT_RESTART;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_CURRENT_ARTICLES;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_CURRENT_FILE;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_CURRENT_POSITIONS;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_CURRENT_TAB;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_FILE_SEARCHED;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
 import static org.kiwix.kiwixmobile.utils.StyleUtils.dialogStyle;
 
 public class KiwixMobileActivity extends BaseActivity implements WebViewCallback {
 
-  public static final int REQUEST_FILE_SEARCH = 1236;
-
-  public static final int REQUEST_STORAGE_PERMISSION = 1;
-
-  private static final int REQUEST_FILE_SELECT = 1234;
-
-  private static final int REQUEST_PREFERENCES = 1235;
-
-  private static final int BOOKMARK_CHOSEN_REQUEST = 1;
-
-  public static final String TAG_KIWIX = "kiwix";
-
-  public static final String TAG_FILE_SEARCHED = "searchedarticle";
-
-  private static final String TAG_CURRENT_FILE = "currentzimfile";
-
-  private static final String TAG_CURRENT_ARTICLES = "currentarticles";
-
-  private static final String TAG_CURRENT_POSITIONS = "currentpositions";
-
-  private static final String TAG_CURRENT_TAB = "currenttab";
-
-  public static final String PREF_NIGHT_MODE = "pref_nightmode";
-
-  private static final String PREF_KIWIX_MOBILE = "kiwix-mobile";
-
-  private static final String PREF_BACK_TO_TOP = "pref_backtotop";
-
-  private static final String PREF_HIDE_TOOLBAR = "pref_hidetoolbar";
-
-  private static final String PREF_ZOOM = "pref_zoom_slider";
-
-  private static final String PREF_ZOOM_ENABLED = "pref_zoom_enabled";
-
-  private static final String PREF_FULLSCREEN = "pref_fullscreen";
-
-  private static final String PREF_NEW_TAB_BACKGROUND = "pref_newtab_background";
-
-  public static final String PREF_FULL_TEXT_SEARCH = "pref_full_text_search";
-
-  public static final String PREF_STORAGE = "pref_selected_storage";
-
-  public static final String PREF_STORAGE_TITLE = "pref_selected_title";
-
-  public static final String PREF_EXTERNAL_LINK_POPUP = "pref_external_link_popup";
-
-  public static final String contactEmailAddress = "android@kiwix.org";
-
   public static boolean isFullscreenOpened;
 
   private boolean isBackToTopEnabled = false;
@@ -372,7 +362,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
   @Override
   public void onCreate(Bundle savedInstanceState) {
     SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
-    wifiOnly = sharedPreferences.getBoolean(KiwixSettingsActivity.PREF_WIFI_ONLY, true);
+    wifiOnly = sharedPreferences.getBoolean(PREF_WIFI_ONLY, true);
     nightMode = KiwixSettingsActivity.nightMode(sharedPreferences);
     if (nightMode) {
       setTheme(R.style.AppTheme_Night);
@@ -470,24 +460,24 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
     updateTitle(ZimContentProvider.getZimFileTitle());
 
     Intent i = getIntent();
-    if (i.getBooleanExtra("library", false)) {
+    if (i.getBooleanExtra(EXTRA_LIBRARY, false)) {
       manageZimFiles(2);
     }
     if (i.hasExtra(TAG_FILE_SEARCHED)) {
       searchForTitle(i.getStringExtra(TAG_FILE_SEARCHED));
       selectTab(mWebViews.size() - 1);
     }
-    if (i.hasExtra("choseXURL")) {
+    if (i.hasExtra(EXTRA_CHOSE_X_URL)) {
       newTab();
-      getCurrentWebView().loadUrl(i.getStringExtra("choseXURL"));
+      getCurrentWebView().loadUrl(i.getStringExtra(EXTRA_CHOSE_X_URL));
     }
-    if (i.hasExtra("choseXTitle")) {
+    if (i.hasExtra(EXTRA_CHOSE_X_TITLE)) {
       newTab();
-      getCurrentWebView().loadUrl(i.getStringExtra("choseXTitle"));
+      getCurrentWebView().loadUrl(i.getStringExtra(EXTRA_CHOSE_X_TITLE));
     }
-    if (i.hasExtra("zimFile")) {
+    if (i.hasExtra(EXTRA_ZIM_FILE)) {
-      File file = new File(FileUtils.getFileName(i.getStringExtra("zimFile")));
+      File file = new File(FileUtils.getFileName(i.getStringExtra(EXTRA_ZIM_FILE)));
-      LibraryFragment.mService.cancelNotification(i.getIntExtra("notificationID", 0));
+      LibraryFragment.mService.cancelNotification(i.getIntExtra(EXTRA_NOTIFICATION_ID, 0));
       Uri uri = Uri.fromFile(file);
 
       finish();
@@ -594,9 +584,9 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
     final String zimFile = ZimContentProvider.getZimFile();
     saveTabStates();
     Intent i = new Intent(KiwixMobileActivity.this, SearchActivity.class);
-    i.putExtra("zimFile", zimFile);
+    i.putExtra(EXTRA_ZIM_FILE, zimFile);
     if (isVoice) {
-      i.putExtra("isWidgetVoice", true);
+      i.putExtra(EXTRA_IS_WIDGET_VOICE, true);
     }
     startActivityForResult(i, REQUEST_FILE_SEARCH);
   }
@@ -908,7 +898,8 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
   private void goToBookmarks() {
     saveTabStates();
     Intent intentBookmarks = new Intent(getBaseContext(), BookmarksActivity.class);
-    intentBookmarks.putExtra("bookmark_contents", bookmarks);
+    // FIXME: Looks like EXTRA below isn't used anywhere?
+    intentBookmarks.putExtra(EXTRA_BOOKMARK_CONTENTS, bookmarks);
     startActivityForResult(intentBookmarks, BOOKMARK_CHOSEN_REQUEST);
   }
 
@@ -936,7 +927,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
 
   private void closeFullScreen() {
     toolbarContainer.setVisibility(View.VISIBLE);
-    if (settings.getBoolean(KiwixSettingsActivity.PREF_BOTTOM_TOOLBAR, false)) {
+    if (settings.getBoolean(PREF_BOTTOM_TOOLBAR, false)) {
       pageBottomTabLayout.setVisibility(View.VISIBLE);
       menuBookmarks.setVisible(false);
     }
@@ -966,7 +957,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
   public void sendContactEmail() {
     Intent intent = new Intent(Intent.ACTION_SEND);
     intent.setType("plain/text");
-    intent.putExtra(Intent.EXTRA_EMAIL, new String[] { contactEmailAddress });
+    intent.putExtra(Intent.EXTRA_EMAIL, new String[] {CONTACT_EMAIL_ADDRESS});
     intent.putExtra(Intent.EXTRA_SUBJECT, "Feedback in " +
         LanguageUtils.getCurrentLocale(this).getDisplayLanguage());
     startActivity(Intent.createChooser(intent, ""));
@@ -977,8 +968,8 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
     if (intent.resolveActivity(getPackageManager()) != null) {
       // Show popup with warning that this url is external and could lead to additional costs
       // or may event not work when the user is offline.
-      if (intent.hasExtra("external_link")
+      if (intent.hasExtra(EXTRA_EXTERNAL_LINK)
-          && intent.getBooleanExtra("external_link", false)
+          && intent.getBooleanExtra(EXTRA_EXTERNAL_LINK, false)
           && isExternalLinkPopup) {
         externalLinkPopup(intent);
       } else {
@@ -1065,7 +1056,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
       this.file = file;
       ActivityCompat.requestPermissions(this,
           new String[] { Manifest.permission.READ_EXTERNAL_STORAGE },
-          KiwixMobileActivity.REQUEST_STORAGE_PERMISSION);
+          REQUEST_STORAGE_PERMISSION);
       if (BuildConfig.IS_CUSTOM_APP && Build.VERSION.SDK_INT == Build.VERSION_CODES.M) {
         Toast.makeText(this, getResources().getString(R.string.request_storage_custom), Toast.LENGTH_LONG)
             .show();
@@ -1081,7 +1072,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
   public void onRequestPermissionsResult(int requestCode,
       String permissions[], int[] grantResults) {
     switch (requestCode) {
-      case KiwixMobileActivity.REQUEST_STORAGE_PERMISSION: {
+      case REQUEST_STORAGE_PERMISSION: {
         if (grantResults.length > 0
             && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
           finish();
@@ -1140,7 +1131,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
         @Override
         public boolean onMenuItemClick(MenuItem item) {
           Intent i = new Intent(KiwixMobileActivity.this, SearchActivity.class);
-          i.putExtra("zimFile", zimFile);
+          i.putExtra(EXTRA_ZIM_FILE, zimFile);
           startActivityForResult(i, REQUEST_FILE_SEARCH);
           overridePendingTransition(0, 0);
           return true;
@@ -1151,7 +1142,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
         @Override
         public void onClick(View v) {
           Intent i = new Intent(KiwixMobileActivity.this, SearchActivity.class);
-          i.putExtra("zimFile", zimFile);
+          i.putExtra(EXTRA_ZIM_FILE, zimFile);
           startActivityForResult(i, REQUEST_FILE_SEARCH);
           overridePendingTransition(0, 0);
         }
@@ -1287,7 +1278,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
       mWebViews.get(currentWebViewIndex).findViewById(R.id.get_content_card).setEnabled(true);
     }
 
-    if (settings.getBoolean(KiwixSettingsActivity.PREF_BOTTOM_TOOLBAR, false)) {
+    if (settings.getBoolean(PREF_BOTTOM_TOOLBAR, false)) {
       pageBottomTabLayout.setVisibility(View.VISIBLE);
       if (menuBookmarks != null) {
         menuBookmarks.setVisible(false);
@@ -1307,7 +1298,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
         final String zimFile = ZimContentProvider.getZimFile();
         saveTabStates();
         Intent i = new Intent(KiwixMobileActivity.this, SearchActivity.class);
-        i.putExtra("zimFile", zimFile);
+        i.putExtra(EXTRA_ZIM_FILE, zimFile);
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
           i.putExtra(Intent.EXTRA_PROCESS_TEXT, intent.getStringExtra(Intent.EXTRA_PROCESS_TEXT));
         }
@@ -1326,8 +1317,8 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
         final String zimFile = ZimContentProvider.getZimFile();
         saveTabStates();
         Intent i = new Intent(KiwixMobileActivity.this, SearchActivity.class);
-        i.putExtra("zimFile", zimFile);
+        i.putExtra(EXTRA_ZIM_FILE, zimFile);
-        i.putExtra("search", intent.getData().getLastPathSegment());
+        i.putExtra(EXTRA_SEARCH, intent.getData().getLastPathSegment());
         intent.setAction("");
         startActivityForResult(i, REQUEST_FILE_SEARCH);
       }
@@ -1339,9 +1330,9 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
   @Override
   protected void onNewIntent(Intent intent) {
     super.onNewIntent(intent);
-    boolean isWidgetSearch = intent.getBooleanExtra("isWidgetSearch", false);
+    boolean isWidgetSearch = intent.getBooleanExtra(EXTRA_IS_WIDGET_SEARCH, false);
-    boolean isWidgetVoiceSearch = intent.getBooleanExtra("isWidgetVoice", false);
+    boolean isWidgetVoiceSearch = intent.getBooleanExtra(EXTRA_IS_WIDGET_VOICE, false);
-    boolean isWidgetStar = intent.getBooleanExtra("isWidgetStar", false);
+    boolean isWidgetStar = intent.getBooleanExtra(EXTRA_IS_WIDGET_STAR, false);
 
     if (isWidgetStar && ZimContentProvider.getId() != null) {
       goToBookmarks();
@@ -1539,11 +1530,11 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
         }
         break;
       case REQUEST_PREFERENCES:
-        if (resultCode == KiwixSettingsActivity.RESULT_RESTART) {
+        if (resultCode == RESULT_RESTART) {
           finish();
           startActivity(new Intent(KiwixMobileActivity.this, KiwixMobileActivity.class));
         }
-        if (resultCode == KiwixSettingsActivity.RESULT_HISTORY_CLEARED) {
+        if (resultCode == RESULT_HISTORY_CLEARED) {
           mWebViews.clear();
           newTab();
           tabDrawerAdapter.notifyDataSetChanged();
@@ -1553,7 +1544,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
 
       case BOOKMARK_CHOSEN_REQUEST:
         if (resultCode == RESULT_OK) {
-          boolean itemClicked = data.getBooleanExtra("bookmarkClicked", false);
+          boolean itemClicked = data.getBooleanExtra(EXTRA_BOOKMARK_CLICKED, false);
           if (ZimContentProvider.getId() == null) return;
 
           //Bookmarks
@@ -1562,13 +1553,13 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
 
           if (itemClicked) {
             String bookmarkChosen;
-            if (data.getStringExtra("choseXURL") != null) {
+            if (data.getStringExtra(EXTRA_CHOSE_X_URL) != null) {
-              bookmarkChosen = data.getStringExtra("choseXURL");
+              bookmarkChosen = data.getStringExtra(EXTRA_CHOSE_X_URL);
               newTab();
               getCurrentWebView().loadUrl(bookmarkChosen);
             } else {
               newTab();
-              bookmarkChosen = data.getStringExtra("choseXTitle");
+              bookmarkChosen = data.getStringExtra(EXTRA_CHOSE_X_TITLE);
               openArticleFromBookmarkTitle(bookmarkChosen);
             }
           }
@@ -1604,7 +1595,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
 
     if (PreferenceManager
         .getDefaultSharedPreferences(getApplicationContext())
-        .getBoolean(KiwixSettingsActivity.PREF_BOTTOM_TOOLBAR, false)) {
+        .getBoolean(PREF_BOTTOM_TOOLBAR, false)) {
       menu.findItem(R.id.menu_bookmarks).setVisible(false);
     }
 
@@ -1741,7 +1732,8 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
   public void selectSettings() {
     final String zimFile = ZimContentProvider.getZimFile();
     Intent i = new Intent(this, KiwixSettingsActivity.class);
-    i.putExtra("zim_file", zimFile);
+    // FIXME: I think line below is redundant - it's not used anywhere
+    i.putExtra(EXTRA_ZIM_FILE_2, zimFile);
     startActivityForResult(i, REQUEST_PREFERENCES);
   }
 
@@ -1832,7 +1824,7 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
             SharedPreferences sharedPreferences =
                 PreferenceManager.getDefaultSharedPreferences(this);
             SharedPreferences.Editor editor = sharedPreferences.edit();
-            editor.putString("pref_language_chooser", BuildConfig.ENFORCED_LANG);
+            editor.putString(PREF_LANG, BuildConfig.ENFORCED_LANG);
             editor.apply();
 
             // restart activity for new locale to take effect
@@ -1925,13 +1917,13 @@ public class KiwixMobileActivity extends BaseActivity implements WebViewCallback
     progressBar.setProgress(progress);
     if (progress == 100) {
       if (requestClearHistoryAfterLoad) {
-        Log.d(KiwixMobileActivity.TAG_KIWIX,
+        Log.d(TAG_KIWIX,
             "Loading article finished and requestClearHistoryAfterLoad -> clearHistory");
         getCurrentWebView().clearHistory();
         requestClearHistoryAfterLoad = false;
       }
 
-      Log.d(KiwixMobileActivity.TAG_KIWIX, "Loaded URL: " + getCurrentWebView().getUrl());
+      Log.d(TAG_KIWIX, "Loaded URL: " + getCurrentWebView().getUrl());
     }
   }
 

app/src/main/java/org/kiwix/kiwixmobile/KiwixWebViewClient.java

@@ -14,6 +14,9 @@ import org.kiwix.kiwixmobile.utils.StyleUtils;
 
 import java.util.HashMap;
 
+import static org.kiwix.kiwixmobile.utils.Constants.CONTACT_EMAIL_ADDRESS;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_EXTERNAL_LINK;
+
 public class KiwixWebViewClient extends WebViewClient {
 
   private static final HashMap<String, String> DOCUMENT_TYPES = new HashMap<String, String>() {{
@@ -56,7 +59,7 @@ public class KiwixWebViewClient extends WebViewClient {
 
     // Otherwise, the link is not for a page on my site, so launch another Activity that handles URLs
     Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
-    intent.putExtra("external_link", true);
+    intent.putExtra(EXTRA_EXTERNAL_LINK, true);
     callback.openExternalUrl(intent);
     return true;
   }
@@ -86,8 +89,7 @@ public class KiwixWebViewClient extends WebViewClient {
             );
         view.addView(help);
         TextView contact = (TextView) help.findViewById(R.id.welcome21);
-        contact.setText(StyleUtils.highlightUrl(contact.getText().toString(),
+        contact.setText(StyleUtils.highlightUrl(contact.getText().toString(), CONTACT_EMAIL_ADDRESS));
-            KiwixMobileActivity.contactEmailAddress));
         contact.setOnClickListener(v -> {
           callback.sendContactEmail();
         });

app/src/main/java/org/kiwix/kiwixmobile/SearchActivity.java

@@ -20,7 +20,6 @@ import android.view.View;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
 import android.widget.ListView;
-import android.widget.RelativeLayout;
 import android.widget.TextView;
 import android.widget.Toast;
 
@@ -32,6 +31,10 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
 
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_IS_WIDGET_VOICE;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_SEARCH;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_NIGHTMODE;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_FILE_SEARCHED;
 import static org.kiwix.kiwixmobile.utils.StyleUtils.dialogStyle;
 
 public class SearchActivity extends AppCompatActivity
@@ -47,7 +50,7 @@ public class SearchActivity extends AppCompatActivity
   @Override
   protected void onCreate(Bundle savedInstanceState) {
     SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
-    if (sharedPreferences.getBoolean(KiwixMobileActivity.PREF_NIGHT_MODE, false)) {
+    if (sharedPreferences.getBoolean(PREF_NIGHTMODE, false)) {
       setTheme(R.style.AppTheme_Night);
     }
     super.onCreate(savedInstanceState);
@@ -70,7 +73,7 @@ public class SearchActivity extends AppCompatActivity
     mListView.setOnItemClickListener(this);
     mListView.setOnItemLongClickListener(this);
 
-    boolean IS_VOICE_SEARCH_INTENT = getIntent().getBooleanExtra("isWidgetVoice", false);
+    boolean IS_VOICE_SEARCH_INTENT = getIntent().getBooleanExtra(EXTRA_IS_WIDGET_VOICE, false);
     if (IS_VOICE_SEARCH_INTENT) {
       promptSpeechInput();
     }
@@ -133,8 +136,8 @@ public class SearchActivity extends AppCompatActivity
       searchView.setQuery(getIntent().getStringExtra(Intent.EXTRA_PROCESS_TEXT), true);
     }
 
-    if (getIntent().hasExtra("search")) {
+    if (getIntent().hasExtra(EXTRA_SEARCH)) {
-      searchView.setQuery(getIntent().getStringExtra("search"), true);
+      searchView.setQuery(getIntent().getStringExtra(EXTRA_SEARCH), true);
     }
 
     return true;
@@ -151,11 +154,11 @@ public class SearchActivity extends AppCompatActivity
     int value = Settings.System.getInt(getContentResolver(), Settings.System.ALWAYS_FINISH_ACTIVITIES, 0);
     if (value == 1) {
       Intent i = new Intent(this, KiwixMobileActivity.class);
-      i.putExtra(KiwixMobileActivity.TAG_FILE_SEARCHED, uri);
+      i.putExtra(TAG_FILE_SEARCHED, uri);
       startActivity(i);
     } else {
       Intent i = new Intent();
-      i.putExtra(KiwixMobileActivity.TAG_FILE_SEARCHED, uri);
+      i.putExtra(TAG_FILE_SEARCHED, uri);
       setResult(RESULT_OK, i);
       finish();
     }

app/src/main/java/org/kiwix/kiwixmobile/ZimContentProvider.java

@@ -51,9 +51,9 @@ import java.util.regex.Pattern;
 import javax.inject.Inject;
 import org.kiwix.kiwixmobile.utils.files.FileUtils;
 
-public class ZimContentProvider extends ContentProvider {
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
 
-  public static final String TAG_KIWIX = "kiwix";
+public class ZimContentProvider extends ContentProvider {
 
   public static final Uri CONTENT_URI = Uri.parse("content://" + BuildConfig.APPLICATION_ID + ".zim.base/");
 

app/src/main/java/org/kiwix/kiwixmobile/bookmarks_view/BookmarksActivity.java

@@ -58,6 +58,10 @@ import javax.inject.Inject;
 import butterknife.BindView;
 import butterknife.ButterKnife;
 
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_BOOKMARK_CLICKED;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_CHOSE_X_TITLE;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_CHOSE_X_URL;
+
 public class BookmarksActivity extends BaseActivity
     implements AdapterView.OnItemClickListener, BookmarksViewCallback {
 
@@ -143,11 +147,11 @@ public class BookmarksActivity extends BaseActivity
   public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
     Intent intent = new Intent(this, KiwixMobileActivity.class);
     if (!bookmarkUrls.get(position).equals("null")) {
-      intent.putExtra("choseXURL", bookmarkUrls.get(position));
+      intent.putExtra(EXTRA_CHOSE_X_URL, bookmarkUrls.get(position));
     } else {
-      intent.putExtra("choseXTitle", bookmarks.get(position));
+      intent.putExtra(EXTRA_CHOSE_X_TITLE, bookmarks.get(position));
     }
-    intent.putExtra("bookmarkClicked", true);
+    intent.putExtra(EXTRA_BOOKMARK_CLICKED, true);
     int value = Settings.System.getInt(getContentResolver(), Settings.System.ALWAYS_FINISH_ACTIVITIES, 0);
     if (value == 1) {
       startActivity(intent);
@@ -162,7 +166,7 @@ public class BookmarksActivity extends BaseActivity
   public void onBackPressed() {
     int value = Settings.System.getInt(getContentResolver(), Settings.System.ALWAYS_FINISH_ACTIVITIES, 0);
     Intent startIntent = new Intent(this, KiwixMobileActivity.class);
-    startIntent.putExtra("bookmarkClicked", false);
+    startIntent.putExtra(EXTRA_BOOKMARK_CLICKED, false);
 
     if (value == 1) { // means there's only 1 activity in stack so start new
       startActivity(startIntent);

app/src/main/java/org/kiwix/kiwixmobile/database/KiwixDatabase.java

@@ -40,6 +40,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
+
 public class KiwixDatabase extends SquidDatabase {
 
   private static final int VERSION = 14;
@@ -155,13 +157,13 @@ public class KiwixDatabase extends SquidDatabase {
               bookmarksDao.saveBookmark(null, in, idName, idName);
             }
             context.deleteFile(id);
-            Log.d(KiwixMobileActivity.TAG_KIWIX, "Switched to bookmarkfile " + ZimContentProvider.getId());
+            Log.d(TAG_KIWIX, "Switched to bookmarkfile " + ZimContentProvider.getId());
           }
         } catch (FileNotFoundException e) {
-          Log.e(KiwixMobileActivity.TAG_KIWIX, "Bookmark File ( " + id + " ) not found", e);
+          Log.e(TAG_KIWIX, "Bookmark File ( " + id + " ) not found", e);
           //TODO: Surface to user
         } catch (IOException e) {
-          Log.e(KiwixMobileActivity.TAG_KIWIX, "Can not read file " + id, e);
+          Log.e(TAG_KIWIX, "Can not read file " + id, e);
           //TODO: Surface to user
         }
       }

app/src/main/java/org/kiwix/kiwixmobile/downloader/DownloadFragment.java

@@ -40,6 +40,7 @@ import org.kiwix.kiwixmobile.zim_manager.library_view.LibraryFragment;
 import java.util.Arrays;
 import java.util.LinkedHashMap;
 
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_WIFI_ONLY;
 import static org.kiwix.kiwixmobile.utils.StyleUtils.dialogStyle;
 
 
@@ -94,7 +95,7 @@ public class DownloadFragment extends Fragment {
             .setPositiveButton(R.string.yes, (dialog, i) -> {
               PreferenceManager.getDefaultSharedPreferences(context)
                       .edit()
-                      .putBoolean(KiwixSettingsActivity.PREF_WIFI_ONLY, false)
+                      .putBoolean(PREF_WIFI_ONLY, false)
                       .apply();
               KiwixMobileActivity.wifiOnly = false;
               yesAction.run();

app/src/main/java/org/kiwix/kiwixmobile/downloader/DownloadService.java

@@ -47,6 +47,11 @@ import okio.BufferedSource;
 import rx.Observable;
 import rx.android.schedulers.AndroidSchedulers;
 
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_BOOK;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_LIBRARY;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_NOTIFICATION_ID;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_ZIM_FILE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_STORAGE;
 import static org.kiwix.kiwixmobile.utils.files.FileUtils.getCurrentSize;
 
 public class DownloadService extends Service {
@@ -94,7 +99,7 @@ public class DownloadService extends Service {
     setupDagger();
 
     SD_CARD = PreferenceManager.getDefaultSharedPreferences(getApplicationContext())
-        .getString(KiwixMobileActivity.PREF_STORAGE,Environment.getExternalStorageDirectory().getPath());
+        .getString(PREF_STORAGE,Environment.getExternalStorageDirectory().getPath());
     KIWIX_ROOT = SD_CARD + "/Kiwix/";
 
     KIWIX_ROOT = checkWritable(KIWIX_ROOT);
@@ -130,7 +135,7 @@ public class DownloadService extends Service {
 
 
     SD_CARD = PreferenceManager.getDefaultSharedPreferences(getApplicationContext())
-        .getString(KiwixMobileActivity.PREF_STORAGE,Environment.getExternalStorageDirectory().getPath());
+        .getString(PREF_STORAGE,Environment.getExternalStorageDirectory().getPath());
     KIWIX_ROOT = SD_CARD + "/Kiwix/";
 
     KIWIX_ROOT = checkWritable(KIWIX_ROOT);
@@ -138,7 +143,7 @@ public class DownloadService extends Service {
     Log.d(KIWIX_TAG, "Using KIWIX_ROOT: " + KIWIX_ROOT);
 
     notificationTitle = intent.getExtras().getString(DownloadIntent.DOWNLOAD_ZIM_TITLE);
-    LibraryNetworkEntity.Book book = (LibraryNetworkEntity.Book) intent.getSerializableExtra("Book");
+    LibraryNetworkEntity.Book book = (LibraryNetworkEntity.Book) intent.getSerializableExtra(EXTRA_BOOK);
     int notificationID = book.getId().hashCode();
 
     if ( downloadStatus.get(notificationID, -1) == PAUSE || downloadStatus.get(notificationID, -1) == PLAY ) {
@@ -147,7 +152,7 @@ public class DownloadService extends Service {
 
     notifications.add(notificationTitle);
     final Intent target = new Intent(this, KiwixMobileActivity.class);
-    target.putExtra("library", true);
+    target.putExtra(EXTRA_LIBRARY, true);
     bookDao = new BookDao(KiwixDatabase.getInstance(this));
 
     PendingIntent pendingIntent = PendingIntent.getActivity
@@ -280,8 +285,8 @@ public class DownloadService extends Service {
             notification.get(notificationID).setContentTitle(notificationTitle + " " + getResources().getString(R.string.zim_file_downloaded));
             notification.get(notificationID).setContentText(getString(R.string.zim_file_downloaded));
             final Intent target = new Intent(this, KiwixMobileActivity.class);
-            target.putExtra("zimFile", KIWIX_ROOT + StorageUtils.getFileNameFromUrl(book.getUrl()));
+            target.putExtra(EXTRA_ZIM_FILE, KIWIX_ROOT + StorageUtils.getFileNameFromUrl(book.getUrl()));
-            target.putExtra("notificationID", notificationID);
+            target.putExtra(EXTRA_NOTIFICATION_ID, notificationID);
             PendingIntent pendingIntent = PendingIntent.getActivity
                 (getBaseContext(), 0,
                     target, PendingIntent.FLAG_CANCEL_CURRENT);

app/src/main/java/org/kiwix/kiwixmobile/settings/KiwixSettingsActivity.java

@@ -57,41 +57,28 @@ import java.util.Locale;
 import eu.mhutti1.utils.storage.StorageDevice;
 import eu.mhutti1.utils.storage.StorageSelectDialog;
 
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_WEBVIEWS_LIST;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_AUTONIGHTMODE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_CLEAR_ALL_HISTORY;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_CREDITS;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_LANG;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_NIGHTMODE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_STORAGE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_STORAGE_TITLE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_VERSION;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_WIFI_ONLY;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_ZOOM;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_ZOOM_ENABLED;
+import static org.kiwix.kiwixmobile.utils.Constants.RESULT_HISTORY_CLEARED;
+import static org.kiwix.kiwixmobile.utils.Constants.RESULT_RESTART;
 import static org.kiwix.kiwixmobile.utils.StyleUtils.dialogStyle;
 
 public class KiwixSettingsActivity extends AppCompatActivity {
 
-  public static final int RESULT_RESTART = 1236;
-
-  public static final int RESULT_HISTORY_CLEARED = 1239;
-
-  public static final String PREF_LANG = "pref_language_chooser";
-
-  public static final String PREF_VERSION = "pref_version";
-
-  public static final String PREF_ZOOM_ENABLED = "pref_zoom_enabled";
-
-  public static final String PREF_ZOOM = "pref_zoom_slider";
-
-  public static final String PREF_CLEAR_ALL_HISTORY = "pref_clear_all_history";
-
-  public static final String PREF_CREDITS = "pref_credits";
-
-  public static final String PREF_STORAGE = "pref_select_folder";
-
-  public static final String PREF_AUTONIGHTMODE = "pref_auto_nightmode";
-
-  public static final String PREF_NIGHTMODE = "pref_nightmode";
-
-  public static final String PREF_WIFI_ONLY = "pref_wifi_only";
-
-  public static final String PREF_BOTTOM_TOOLBAR = "pref_bottomtoolbar";
-
   public static String zimFile;
 
   public static boolean allHistoryCleared = false;
 
-
   private static final int DAWN_HOUR = 6;
   private static final int DUSK_HOUR = 18;
 
@@ -120,7 +107,7 @@ public class KiwixSettingsActivity extends AppCompatActivity {
   public void onBackPressed() {
     if (allHistoryCleared) {
       Intent data = new Intent();
-      data.putExtra("webviewsList", allHistoryCleared);
+      data.putExtra(EXTRA_WEBVIEWS_LIST, allHistoryCleared);
       setResult(RESULT_HISTORY_CLEARED, data);
     }
     super.onBackPressed();
@@ -195,13 +182,13 @@ public class KiwixSettingsActivity extends AppCompatActivity {
       } else {
         if (Environment.isExternalStorageEmulated()) {
           getPrefrence(PREF_STORAGE).setTitle(PreferenceManager.getDefaultSharedPreferences(getActivity())
-              .getString(KiwixMobileActivity.PREF_STORAGE_TITLE, "Internal"));
+              .getString(PREF_STORAGE_TITLE, "Internal"));
         } else {
           getPrefrence(PREF_STORAGE).setTitle(PreferenceManager.getDefaultSharedPreferences(getActivity())
-              .getString(KiwixMobileActivity.PREF_STORAGE_TITLE, "External"));
+              .getString(PREF_STORAGE_TITLE, "External"));
         }
         getPrefrence(PREF_STORAGE).setSummary(LibraryUtils.bytesToHuman( new File(PreferenceManager.getDefaultSharedPreferences(getActivity())
-            .getString(KiwixMobileActivity.PREF_STORAGE, Environment.getExternalStorageDirectory().getPath())).getFreeSpace()));
+            .getString(PREF_STORAGE, Environment.getExternalStorageDirectory().getPath())).getFreeSpace()));
       }
     }
 
@@ -369,13 +356,13 @@ public class KiwixSettingsActivity extends AppCompatActivity {
       findPreference(PREF_STORAGE).setSummary(storageDevice.getSize());
       SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getActivity());
       SharedPreferences.Editor editor = sharedPreferences.edit();
-      editor.putString(KiwixMobileActivity.PREF_STORAGE,storageDevice.getName());
+      editor.putString(PREF_STORAGE,storageDevice.getName());
       if (storageDevice.isInternal()) {
         findPreference(PREF_STORAGE).setTitle(getResources().getString(R.string.internal_storage));
-        editor.putString(KiwixMobileActivity.PREF_STORAGE_TITLE, getResources().getString(R.string.internal_storage));
+        editor.putString(PREF_STORAGE_TITLE, getResources().getString(R.string.internal_storage));
       } else {
         findPreference(PREF_STORAGE).setTitle(getResources().getString(R.string.external_storage));
-        editor.putString(KiwixMobileActivity.PREF_STORAGE_TITLE, getResources().getString(R.string.external_storage));
+        editor.putString(PREF_STORAGE_TITLE, getResources().getString(R.string.external_storage));
       }
       editor.apply();
     }

app/src/main/java/org/kiwix/kiwixmobile/utils/Constants.java

@@ -0,0 +1,105 @@
+package org.kiwix.kiwixmobile.utils;
+
+public final class Constants {
+
+    public static final String TAG_KIWIX = "kiwix";
+
+    public static final String CONTACT_EMAIL_ADDRESS = "android@kiwix.org";
+
+    // Request stuff
+    public static final int REQUEST_FILE_SEARCH = 1236;
+
+    public static final int REQUEST_STORAGE_PERMISSION = 1;
+
+    public static final int REQUEST_FILE_SELECT = 1234;
+
+    public static final int REQUEST_PREFERENCES = 1235;
+
+    public static final int BOOKMARK_CHOSEN_REQUEST = 1;
+
+    // Result stuff
+    public static final int RESULT_RESTART = 1236;
+
+    public static final int RESULT_HISTORY_CLEARED = 1239;
+
+    // Prefs
+    public static final String PREF_LANG = "pref_language_chooser";
+
+    public static final String PREF_VERSION = "pref_version";
+
+    public static final String PREF_CLEAR_ALL_HISTORY = "pref_clear_all_history";
+
+    public static final String PREF_CREDITS = "pref_credits";
+
+    public static final String PREF_STORAGE = "pref_select_folder";
+
+    public static final String PREF_AUTONIGHTMODE = "pref_auto_nightmode";
+
+    public static final String PREF_NIGHTMODE = "pref_nightmode";
+
+    public static final String PREF_WIFI_ONLY = "pref_wifi_only";
+
+    public static final String PREF_BOTTOM_TOOLBAR = "pref_bottomtoolbar";
+
+    public static final String PREF_KIWIX_MOBILE = "kiwix-mobile";
+
+    public static final String PREF_BACK_TO_TOP = "pref_backtotop";
+
+    public static final String PREF_HIDE_TOOLBAR = "pref_hidetoolbar";
+
+    public static final String PREF_ZOOM = "pref_zoom_slider";
+
+    public static final String PREF_ZOOM_ENABLED = "pref_zoom_enabled";
+
+    public static final String PREF_FULLSCREEN = "pref_fullscreen";
+
+    public static final String PREF_NEW_TAB_BACKGROUND = "pref_newtab_background";
+
+    public static final String PREF_FULL_TEXT_SEARCH = "pref_full_text_search";
+
+    public static final String PREF_STORAGE_TITLE = "pref_selected_title";
+
+    public static final String PREF_EXTERNAL_LINK_POPUP = "pref_external_link_popup";
+
+    // Tags
+    public static final String TAG_FILE_SEARCHED = "searchedarticle";
+
+    public static final String TAG_CURRENT_FILE = "currentzimfile";
+
+    public static final String TAG_CURRENT_ARTICLES = "currentarticles";
+
+    public static final String TAG_CURRENT_POSITIONS = "currentpositions";
+
+    public static final String TAG_CURRENT_TAB = "currenttab";
+
+    // Extras
+    public static final String EXTRA_ZIM_FILE_2 = "zim_file";
+
+    public static final String EXTRA_ZIM_FILE = "zimFile";
+
+    public static final String EXTRA_CHOSE_X_URL = "choseXURL";
+
+    public static final String EXTRA_CHOSE_X_TITLE = "choseXTitle";
+
+    public static final String EXTRA_EXTERNAL_LINK = "external_link";
+
+    public static final String EXTRA_LIBRARY = "library";
+
+    public static final String EXTRA_SEARCH = "search";
+
+    public static final String EXTRA_BOOKMARK_CLICKED = "bookmarkClicked";
+
+    public static final String EXTRA_BOOK = "Book";
+
+    public static final String EXTRA_IS_WIDGET_VOICE = "isWidgetVoice";
+
+    public static final String EXTRA_IS_WIDGET_SEARCH = "isWidgetSearch";
+
+    public static final String EXTRA_IS_WIDGET_STAR = "isWidgetStar";
+
+    public static final String EXTRA_NOTIFICATION_ID = "notificationID";
+
+    public static final String EXTRA_WEBVIEWS_LIST = "webviewsList";
+
+    public static final String EXTRA_BOOKMARK_CONTENTS = "bookmark_contents";
+}

app/src/main/java/org/kiwix/kiwixmobile/utils/KiwixTextToSpeech.java

@@ -21,9 +21,9 @@ import java.util.List;
 import java.util.Locale;
 import java.util.concurrent.atomic.AtomicInteger;
 
-public class KiwixTextToSpeech {
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
 
-  public static final String TAG_KIWIX = "kiwix";
+public class KiwixTextToSpeech {
 
   private Context context;
 

app/src/main/java/org/kiwix/kiwixmobile/utils/LanguageUtils.java

@@ -48,9 +48,11 @@ import java.util.List;
 import java.util.Locale;
 import java.util.MissingResourceException;
 
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_LANG;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
+
 public class LanguageUtils {
 
-  public static final String TAG_KIWIX = "kiwix";
   private static HashMap<String, Locale> mLocaleMap;
   private List<LanguageContainer> mLanguageList;
   private List<String> mLocaleLanguageCodes;
@@ -68,7 +70,7 @@ public class LanguageUtils {
   public static void handleLocaleChange(Context context) {
 
     SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-    String language = prefs.getString("pref_language_chooser", "");
+    String language = prefs.getString(PREF_LANG, "");
 
     if (language.isEmpty()) {
       return;
@@ -167,7 +169,7 @@ public class LanguageUtils {
 
       // Don't change the language, if the options hasn't been set
       SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
-      String language = prefs.getString("pref_language_chooser", "");
+      String language = prefs.getString(PREF_LANG, "");
 
       if (language.isEmpty()) {
         return false;

app/src/main/java/org/kiwix/kiwixmobile/utils/NetworkUtils.java

@@ -11,6 +11,8 @@ import org.kiwix.kiwixmobile.R;
 
 import java.util.UUID;
 
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
+
 public class NetworkUtils {
 
   public static boolean isNetworkAvailable(Context context) {
@@ -77,7 +79,7 @@ public class NetworkUtils {
       details = details.trim().replaceAll(" +", " ");
       return details;
     } catch (Exception e) {
-      Log.d(KiwixMobileActivity.TAG_KIWIX, "Context invalid url: " + url, e);
+      Log.d(TAG_KIWIX, "Context invalid url: " + url, e);
       return "";
     }
   }

app/src/main/java/org/kiwix/kiwixmobile/utils/files/FileSearch.java

@@ -38,9 +38,9 @@ import java.util.Vector;
 import eu.mhutti1.utils.storage.StorageDevice;
 import eu.mhutti1.utils.storage.StorageDeviceUtils;
 
-public class FileSearch {
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
 
-  public static final String TAG_KIWIX = "kiwix";
+public class FileSearch {
 
   // Array of zim file extensions
   public static final String[] zimFiles = {"zim", "zimaa"};

app/src/main/java/org/kiwix/kiwixmobile/utils/files/FileUtils.java

@@ -19,9 +19,9 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-public class FileUtils {
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
 
-  public static final String TAG_KIWIX = "kiwix";
+public class FileUtils {
 
   public static File getFileCacheDir(Context context) {
     boolean external = Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState());

app/src/main/java/org/kiwix/kiwixmobile/views/AutoCompleteAdapter.java

@@ -22,6 +22,8 @@ import java.util.List;
 
 import javax.inject.Inject;
 
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_FULL_TEXT_SEARCH;
+
 public class AutoCompleteAdapter extends ArrayAdapter<String> implements Filterable {
 
   private List<String> mData;
@@ -82,9 +84,9 @@ public class AutoCompleteAdapter extends ArrayAdapter<String> implements Filtera
 	  /* Get search request */
 	  final String query = constraint.toString();
 
-          /* Fulltex search */
+          /* Fulltext search */
           SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
-          if (sharedPreferences.getBoolean(KiwixMobileActivity.PREF_FULL_TEXT_SEARCH, false)) {
+          if (sharedPreferences.getBoolean(PREF_FULL_TEXT_SEARCH, false)) {
             ZimContentProvider.jniSearcher.search(query, 200);
             JNIKiwixSearcher.Result result = ZimContentProvider.jniSearcher.getNextResult();
             while (result != null) {

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/fileselect_view/ZimFileSelectFragment.java

@@ -70,13 +70,15 @@ import java.util.List;
 
 import javax.inject.Inject;
 
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_STORAGE;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_STORAGE_PERMISSION;
+import static org.kiwix.kiwixmobile.utils.Constants.TAG_KIWIX;
 import static org.kiwix.kiwixmobile.utils.NetworkUtils.parseURL;
 import static org.kiwix.kiwixmobile.utils.StyleUtils.dialogStyle;
 
 public class ZimFileSelectFragment extends Fragment
     implements OnItemClickListener, AdapterView.OnItemLongClickListener, ZimFileSelectViewCallback{
 
-  public static final String TAG_KIWIX = "kiwix";
   public static ZimManageActivity context;
   public RelativeLayout llLayout;
   public SwipeRefreshLayout swipeRefreshLayout;
@@ -207,7 +209,7 @@ public class ZimFileSelectFragment extends Fragment
       Toast.makeText(super.getActivity(), getResources().getString(R.string.request_storage), Toast.LENGTH_LONG)
           .show();
         requestPermissions( new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
-            KiwixMobileActivity.REQUEST_STORAGE_PERMISSION);
+            REQUEST_STORAGE_PERMISSION);
     } else {
       getFiles();
     }
@@ -268,14 +270,14 @@ public class ZimFileSelectFragment extends Fragment
         });
       }
     }).scan(PreferenceManager.getDefaultSharedPreferences(context)
-        .getString(KiwixMobileActivity.PREF_STORAGE, Environment.getExternalStorageDirectory().getPath()));
+        .getString(PREF_STORAGE, Environment.getExternalStorageDirectory().getPath()));
   }
 
   @Override
   public void onRequestPermissionsResult(int requestCode,
                                          String permissions[], int[] grantResults) {
     switch (requestCode) {
-      case KiwixMobileActivity.REQUEST_STORAGE_PERMISSION: {
+      case REQUEST_STORAGE_PERMISSION: {
         if (grantResults.length > 0
             && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
             getFiles();

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/library_view/LibraryFragment.java

@@ -60,6 +60,9 @@ import eu.mhutti1.utils.storage.support.StorageSelectDialog;
 
 import static org.kiwix.kiwixmobile.downloader.DownloadService.KIWIX_ROOT;
 import static org.kiwix.kiwixmobile.library.entity.LibraryNetworkEntity.Book;
+import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_BOOK;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_STORAGE;
+import static org.kiwix.kiwixmobile.utils.Constants.PREF_STORAGE_TITLE;
 import static org.kiwix.kiwixmobile.utils.StyleUtils.dialogStyle;
 
 public class LibraryFragment extends Fragment
@@ -290,7 +293,7 @@ public class LibraryFragment extends Fragment
     Intent service = new Intent(super.getActivity(), DownloadService.class);
     service.putExtra(DownloadIntent.DOWNLOAD_URL_PARAMETER, book.getUrl());
     service.putExtra(DownloadIntent.DOWNLOAD_ZIM_TITLE, book.getTitle());
-    service.putExtra("Book", book);
+    service.putExtra(EXTRA_BOOK, book);
     super.getActivity().startService(service);
     mConnection = new DownloadServiceConnection();
     super.getActivity()
@@ -301,7 +304,7 @@ public class LibraryFragment extends Fragment
 
   public long getSpaceAvailable() {
     return new File(PreferenceManager.getDefaultSharedPreferences(super.getActivity())
-        .getString(KiwixMobileActivity.PREF_STORAGE, Environment.getExternalStorageDirectory()
+        .getString(PREF_STORAGE, Environment.getExternalStorageDirectory()
             .getPath())).getFreeSpace();
   }
 
@@ -310,11 +313,11 @@ public class LibraryFragment extends Fragment
     SharedPreferences sharedPreferences =
         PreferenceManager.getDefaultSharedPreferences(getActivity());
     SharedPreferences.Editor editor = sharedPreferences.edit();
-    editor.putString(KiwixMobileActivity.PREF_STORAGE, storageDevice.getName());
+    editor.putString(PREF_STORAGE, storageDevice.getName());
     if (storageDevice.isInternal()) {
-      editor.putString(KiwixMobileActivity.PREF_STORAGE_TITLE, getResources().getString(R.string.internal_storage));
+      editor.putString(PREF_STORAGE_TITLE, getResources().getString(R.string.internal_storage));
     } else {
-      editor.putString(KiwixMobileActivity.PREF_STORAGE_TITLE, getResources().getString(R.string.external_storage));
+      editor.putString(PREF_STORAGE_TITLE, getResources().getString(R.string.external_storage));
     }
     editor.apply();
   }