Merge pull request #1198 from kiwix/feature/NoteKeeper

GSoC 2019 Deliverable: Note Keeper

.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: https://kiwix.org/support-us/

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

@@ -0,0 +1,415 @@
+package org.kiwix.kiwixmobile.main;
+
+import android.Manifest;
+import android.app.Dialog;
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.net.Uri;
+import android.os.Build;
+import android.os.Bundle;
+import android.os.Environment;
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.util.Log;
+import android.view.LayoutInflater;
+import android.view.MenuItem;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.appcompat.widget.Toolbar;
+import androidx.core.content.ContextCompat;
+import androidx.core.content.FileProvider;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.Fragment;
+
+import org.kiwix.kiwixmobile.BuildConfig;
+import org.kiwix.kiwixmobile.R;
+import org.kiwix.kiwixmobile.data.ZimContentProvider;
+import org.kiwix.kiwixmobile.utils.SharedPreferenceUtil;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+
+import butterknife.BindView;
+import butterknife.ButterKnife;
+import butterknife.Unbinder;
+
+import static org.kiwix.kiwixmobile.utils.Constants.NOTES_DIRECTORY;
+
+/**
+ * Created by @author Aditya-Sood (21/05/19) as a part of GSoC 2019
+ *
+ * AddNoteDialog extends DialogFragment and is used to display the note corresponding to a particular
+ * article (of a particular zim file/wiki/book) as a full-screen dialog fragment.
+ *
+ * Notes are saved as text files at location: "{External Storage}/Kiwix/Notes/ZimFileTitle/ArticleTitle.txt"
+ * */
+
+public class AddNoteDialog extends DialogFragment implements ConfirmationAlertDialogFragment.UserClickListener {
+
+  public static String TAG = "AddNoteDialog";
+
+  private SharedPreferenceUtil sharedPreferenceUtil;
+
+  @BindView(R.id.add_note_toolbar)
+  Toolbar toolbar;  // Displays options for the note dialog
+  @BindView(R.id.add_note_text_view)
+  TextView addNoteTextView; // Displays article title
+  @BindView(R.id.add_note_edit_text)
+  EditText addNoteEditText; // Displays zim file title (wiki name)
+
+  private Unbinder unbinder;
+
+  private String zimFileTitle;
+  private String articleTitle;
+  private boolean noteFileExists = false;
+  private boolean noteEdited = false; // Keeps track of state of the note (whether edited since last save)
+
+  public AddNoteDialog(SharedPreferenceUtil sharedPreferenceUtil) {
+    this.sharedPreferenceUtil = sharedPreferenceUtil;
+  }
+
+  @Override
+  public void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+
+    setStyle(DialogFragment.STYLE_NORMAL, sharedPreferenceUtil.nightMode() ? R.style.AddNoteDialogStyle_Night : R.style.AddNoteDialogStyle);
+
+    zimFileTitle = ZimContentProvider.getZimFileTitle();
+    articleTitle = ((MainActivity)getActivity()).getCurrentWebView().getTitle();
+  }
+
+  @Override
+  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+    super.onCreateView(inflater, container, savedInstanceState);
+    View view = inflater.inflate(R.layout.dialog_add_note, container, false);
+    unbinder = ButterKnife.bind(this, view);
+
+    toolbar.setTitle(R.string.note);
+    toolbar.setNavigationIcon(R.drawable.ic_close_white_24dp);
+    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
+      @Override
+      public void onClick(View v) {
+        closeKeyboard();
+        exitAddNoteDialog();
+      }
+    });
+
+    toolbar.setOnMenuItemClickListener(new Toolbar.OnMenuItemClickListener() {
+      @Override
+      public boolean onMenuItemClick(MenuItem item) {
+
+        switch (item.getItemId()) {
+          case R.id.share_note: // Opens app-chooser for sharing the note text file
+            shareNote();
+            break;
+
+          case R.id.save_note:  // Saves the note as a text file
+            saveNote(addNoteEditText.getText().toString());
+            break;
+        }
+        return true;
+      }
+    });
+
+    toolbar.inflateMenu(R.menu.menu_add_note_dialog);
+    // 'Share' disabled for empty notes, 'Save' disabled for unedited notes
+    disableMenuItems();
+
+    addNoteTextView.setText(articleTitle);
+
+    // Show the previously saved note if it exists
+    displayNote();
+
+    addNoteEditText.addTextChangedListener(new TextWatcher() {
+      @Override
+      public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
+
+      @Override
+      public void onTextChanged(CharSequence s, int start, int before, int count) {
+        noteEdited = true;
+        enableSaveNoteMenuItem();
+        enableShareNoteMenuItem();
+      }
+
+      @Override
+      public void afterTextChanged(Editable s) {}
+    });
+
+    return view;
+  }
+
+  // Override onBackPressed() to respond to user pressing 'Back' button on navigation bar
+  @NonNull
+  @Override
+  public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
+    return new Dialog(getActivity(), getTheme()) {
+      @Override
+      public void onBackPressed() {
+        exitAddNoteDialog();
+      }
+    };
+  }
+
+  private void exitAddNoteDialog() {
+    if(noteEdited) {
+      Fragment previousInstance = getActivity().getSupportFragmentManager().findFragmentByTag(ConfirmationAlertDialogFragment.TAG);
+
+      if(previousInstance == null) {
+        // Custom AlertDialog for taking user confirmation before closing note dialog in case of unsaved changes
+        DialogFragment newFragment = new ConfirmationAlertDialogFragment(sharedPreferenceUtil, TAG, R.string.confirmation_alert_dialog_message);
+        newFragment.show(getActivity().getSupportFragmentManager(), ConfirmationAlertDialogFragment.TAG);
+      }
+
+    } else {
+      // Closing unedited note dialog straightaway
+      dismissAddNoteDialog();
+    }
+  }
+
+  private void disableMenuItems() {
+    if(toolbar.getMenu() != null) {
+      MenuItem saveItem = toolbar.getMenu().findItem(R.id.save_note);
+      MenuItem shareItem = toolbar.getMenu().findItem(R.id.share_note);
+      saveItem.setEnabled(false);
+      shareItem.setEnabled(false);
+      saveItem.getIcon().setAlpha(130);
+      shareItem.getIcon().setAlpha(130);
+
+    } else {
+      Log.d(TAG, "Toolbar without inflated menu");
+    }
+  }
+
+  private void enableSaveNoteMenuItem() {
+    if(toolbar.getMenu() != null) {
+      MenuItem saveItem = toolbar.getMenu().findItem(R.id.save_note);
+      saveItem.setEnabled(true);
+      saveItem.getIcon().setAlpha(255);
+
+    } else {
+      Log.d(TAG, "Toolbar without inflated menu");
+    }
+  }
+
+  private void enableShareNoteMenuItem() {
+    if(toolbar.getMenu() != null) {
+      MenuItem shareItem = toolbar.getMenu().findItem(R.id.share_note);
+      shareItem.setEnabled(true);
+      shareItem.getIcon().setAlpha(255);
+
+    } else {
+      Log.d(TAG, "Toolbar without inflated menu");
+    }
+  }
+
+  @Override
+  public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
+    super.onViewCreated(view, savedInstanceState);
+
+    if(!noteFileExists) {
+      // Prepare for input in case of empty/new note
+      addNoteEditText.requestFocus();
+      showKeyboard();
+    }
+  }
+
+  public void showKeyboard(){
+    InputMethodManager inputMethodManager = (InputMethodManager) getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
+    inputMethodManager.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);
+  }
+
+  public void closeKeyboard(){
+    InputMethodManager inputMethodManager = (InputMethodManager) getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
+    inputMethodManager.toggleSoftInput(InputMethodManager.HIDE_IMPLICIT_ONLY, 0);
+  }
+
+  private void saveNote(String noteText) {
+
+    /* String content of the EditText, given by noteText, is saved into the text file given by:
+     *    "{External Storage}/Kiwix/Notes/ZimFileTitle/ArticleTitle.txt"
+     * */
+
+    if(isExternalStorageWritable()) {
+
+      if(ContextCompat.checkSelfPermission(getContext(), Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
+        Log.d(TAG, "WRITE_EXTERNAL_STORAGE permission not granted");
+        showToast(R.string.note_save_unsuccessful, Toast.LENGTH_LONG);
+        return;
+      }
+
+      File notesFolder = new File(NOTES_DIRECTORY + zimFileTitle);
+      boolean folderExists = true;
+
+      if(!notesFolder.exists()) {
+        // Try creating folder if it doesn't exist
+        folderExists = notesFolder.mkdirs();
+      }
+
+      if(folderExists) {
+        File noteFile = new File(notesFolder.getAbsolutePath(), articleTitle + ".txt");
+
+        // Save note text-file code:
+        try {
+          FileOutputStream fileOutputStream = new FileOutputStream(noteFile);
+          fileOutputStream.write(noteText.getBytes());
+          fileOutputStream.close();
+          showToast(R.string.note_save_successful, Toast.LENGTH_SHORT);
+          noteEdited = false; // As no unsaved changes remain
+
+        } catch (IOException e) {
+          e.printStackTrace();
+          showToast(R.string.note_save_unsuccessful, Toast.LENGTH_LONG);
+        }
+
+      } else {
+        showToast(R.string.note_save_unsuccessful, Toast.LENGTH_LONG);
+        Log.d(TAG, "Required folder doesn't exist");
+      }
+    }
+    else {
+      showToast(R.string.note_save_error_storage_not_writable, Toast.LENGTH_LONG);
+    }
+
+  }
+
+  private void displayNote() {
+
+    /* String content of the note text file given at:
+     *    "{External Storage}/Kiwix/Notes/ZimFileTitle/ArticleTitle.txt"
+     * is displayed in the EditText field (note content area)
+     * */
+
+    File noteFile = new File(NOTES_DIRECTORY + zimFileTitle + "/" + articleTitle + ".txt");
+
+    if(noteFile.exists()) {
+      noteFileExists = true;
+
+      StringBuilder contents = new StringBuilder();
+      try {
+
+        BufferedReader input = new BufferedReader(new java.io.FileReader(noteFile));
+        try {
+          String line = null;
+
+          while((line = input.readLine()) != null) {
+            contents.append(line);
+            contents.append(System.getProperty("line.separator"));
+          }
+        } catch (IOException e) {
+          e.printStackTrace();
+          Log.d(TAG, "Error reading line with BufferedReader");
+        } finally {
+          input.close();
+        }
+
+      } catch (IOException e) {
+        e.printStackTrace();
+        Log.d(TAG, "Error closing BufferedReader");
+      }
+
+      addNoteEditText.setText(contents.toString()); // Display the note content
+
+      enableShareNoteMenuItem(); // As note content exists which can be shared
+    }
+
+    // No action in case the note file for the currently open article doesn't exist
+  }
+
+  private void shareNote() {
+
+    /* The note text file corresponding to the currently open article, given at:
+     *    "{External Storage}/Kiwix/Notes/ZimFileTitle/ArticleTitle.txt"
+     * is shared via an app-chooser intent
+     * */
+
+    if(noteEdited) {
+     saveNote(addNoteEditText.getText().toString()); // Save edited note before sharing the text file
+    }
+
+    File noteFile = new File(NOTES_DIRECTORY + zimFileTitle + "/" + articleTitle + ".txt");
+
+    Uri noteFileUri = null;
+    if(noteFile.exists()) {
+
+      if (Build.VERSION.SDK_INT >= 24) {
+        // From Nougat 7 (API 24) access to files is shared temporarily with other apps
+        // Need to use FileProvider for the same
+        noteFileUri = FileProvider.getUriForFile(getContext(), BuildConfig.APPLICATION_ID+".fileprovider", noteFile);
+
+      } else {
+        noteFileUri = Uri.fromFile(noteFile);
+      }
+
+    } else {
+      showToast(R.string.note_share_error_file_missing, Toast.LENGTH_SHORT);
+    }
+
+    if(noteFileUri != null) {
+      Intent noteFileShareIntent = new Intent(Intent.ACTION_SEND);
+      noteFileShareIntent.setType("application/octet-stream");
+      noteFileShareIntent.putExtra(Intent.EXTRA_STREAM, noteFileUri);
+      noteFileShareIntent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+      Intent shareChooser = Intent.createChooser(noteFileShareIntent, getString(R.string.note_share_app_chooser_title));
+
+      if(noteFileShareIntent.resolveActivity(getActivity().getPackageManager()) != null) {
+        startActivity(shareChooser);
+      }
+    }
+  }
+
+  public static boolean isExternalStorageWritable() {
+    return Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState());
+  }
+
+  private void showToast(int stringResource, int duration) {
+    Toast.makeText(getActivity(), stringResource, duration).show();
+  }
+
+  // Methods from ConfirmationAlertDialogFragment.UserClickListener interface
+  @Override
+  public void onPositiveClick() {
+    dismissAddNoteDialog();
+  }
+
+  @Override
+  public void onNegativeClick() {
+    // Do nothing
+  }
+
+  private void dismissAddNoteDialog() {
+    Dialog dialog = getDialog();
+    dialog.dismiss();
+  }
+
+  @Override
+  public void onStart() {
+    super.onStart();
+
+    Dialog dialog = getDialog();
+    if(dialog != null) {
+      int width = ViewGroup.LayoutParams.MATCH_PARENT;
+      int height = ViewGroup.LayoutParams.MATCH_PARENT;
+      dialog.getWindow().setLayout(width, height);
+    }
+  }
+
+  @Override
+  public void onDestroyView() {
+    super.onDestroyView();
+    if (unbinder != null) {
+      unbinder.unbind();
+    }
+  }
+
+}

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

@@ -0,0 +1,83 @@
+package org.kiwix.kiwixmobile.main;
+
+import android.app.Dialog;
+import android.content.DialogInterface;
+import android.os.Bundle;
+
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.Fragment;
+
+import org.kiwix.kiwixmobile.R;
+import org.kiwix.kiwixmobile.utils.SharedPreferenceUtil;
+
+
+/**
+ * Created by @Aditya-Sood as a part of GSoC 2019
+ *
+ * This is a generic helper class for displaying a 2-button (positive & negative) confirmation dialog fragment on top of an existing dialog fragment
+ *  - Only for confirmation dialogs with a Positive & Negative button
+ *  - If you also need a Neutral button, add it selectively (if-else) for the required use case (Take care of the callback interface as well)
+ *
+ * Currently used as:
+ *  - Helper class to show the alert dialog in case the user tries to exit the {@link AddNoteDialog} with unsaved file changes
+ *
+ **/
+
+public class ConfirmationAlertDialogFragment extends DialogFragment {
+
+  public static String TAG = "ConfirmationAlertDialog";
+
+  private SharedPreferenceUtil sharedPreferenceUtil;
+  private int stringResourceId;
+  private String parentDialogFragmentTAG;
+
+  public ConfirmationAlertDialogFragment(SharedPreferenceUtil sharedPreferenceUtil, String parentDialogFragmentTAG, int stringResourceId) {
+    this.sharedPreferenceUtil = sharedPreferenceUtil;
+    this.parentDialogFragmentTAG = parentDialogFragmentTAG;
+    this.stringResourceId = stringResourceId;
+  }
+
+  @Override
+  public Dialog onCreateDialog(Bundle savedInstanceState) {
+    Fragment parentDialogFragment = getFragmentManager().findFragmentByTag(parentDialogFragmentTAG);
+
+    AlertDialog.Builder builder;
+
+    if (sharedPreferenceUtil != null && sharedPreferenceUtil.nightMode()) { // Night Mode support
+      builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog_Night);
+    } else {
+      builder = new AlertDialog.Builder(getActivity());
+    }
+
+    builder.setMessage(stringResourceId)
+        .setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
+          @Override
+          public void onClick(DialogInterface dialog, int which) {
+
+            if(parentDialogFragment != null) {
+              ((UserClickListener) parentDialogFragment).onPositiveClick();
+            }
+          }
+        })
+        .setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
+          @Override
+          public void onClick(DialogInterface dialog, int which) {
+
+            if(parentDialogFragment != null) {
+              ((UserClickListener) parentDialogFragment).onNegativeClick();
+            }
+          }
+        });
+
+    return builder.create();
+  }
+
+  /** Callback interface for responding to user clicks to a {@link ConfirmationAlertDialogFragment} dialog */
+  public interface UserClickListener {
+    void onPositiveClick();
+
+    void onNegativeClick();
+  }
+
+}

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

@@ -25,6 +25,7 @@ import android.appwidget.AppWidgetManager;
 import android.content.ActivityNotFoundException;
 import android.content.ComponentName;
 import android.content.Context;
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
@@ -36,6 +37,7 @@ import android.net.Uri;
 import android.os.Build;
 import android.os.Bundle;
 import android.os.CountDownTimer;
+import android.os.Environment;
 import android.os.Handler;
 import android.provider.Settings;
 import android.text.SpannableString;
@@ -70,6 +72,8 @@ import androidx.core.app.ActivityCompat;
 import androidx.core.content.ContextCompat;
 import androidx.core.view.GravityCompat;
 import androidx.drawerlayout.widget.DrawerLayout;
+import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentTransaction;
 import androidx.recyclerview.widget.ItemTouchHelper;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
@@ -131,11 +135,15 @@ import static org.kiwix.kiwixmobile.utils.Constants.EXTRA_LIBRARY;
 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.NOTES_DIRECTORY;
 import static org.kiwix.kiwixmobile.utils.Constants.PREF_KIWIX_MOBILE;
 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_HISTORY_ITEM_CHOSEN;
 import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_PREFERENCES;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_READ_STORAGE_PERMISSION;
 import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_STORAGE_PERMISSION;
+import static org.kiwix.kiwixmobile.utils.Constants.REQUEST_WRITE_STORAGE_PERMISSION_ADD_NOTE;
 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;
@@ -151,8 +159,6 @@ import static org.kiwix.kiwixmobile.utils.UpdateUtils.reformatProviderUrl;
 public class MainActivity extends BaseActivity implements WebViewCallback,
     MainContract.View{
 
-  private static final int REQUEST_READ_STORAGE_PERMISSION = 2;
-  private static final int REQUEST_HISTORY_ITEM_CHOSEN = 99;
   private static final String NEW_TAB = "NEW_TAB";
   private static final String HOME_URL = "file:///android_asset/home.html";
   public static boolean isFullscreenOpened;
@@ -445,11 +451,7 @@ public class MainActivity extends BaseActivity implements WebViewCallback,
         hideTabSwitcher();
         selectTab(position);
 
-        /* Bug Fix
-         * Issue #592 in which the navigational history of the previously open tab (WebView) was
-         * carried forward to the newly selected/opened tab; causing erroneous enabling of
-         * navigational buttons.
-         */
+        /* Bug Fix #592 */
         updateBottomToolbarArrowsAlpha();
       }
 
@@ -856,6 +858,19 @@ public class MainActivity extends BaseActivity implements WebViewCallback,
         compatCallback.showSoftInput();
         break;
 
+      case R.id.menu_add_note:
+        if(requestExternalStorageWritePermissionForNotes()) {
+          // Check permission since notes are stored in the public-external storage
+          showAddNoteDialog();
+        }
+        break;
+
+      case R.id.menu_clear_notes:
+        if(requestExternalStorageWritePermissionForNotes()) { // Check permission since notes are stored in the public-external storage
+          showClearAllNotesDialog();
+        }
+        break;
+
       case R.id.menu_bookmarks_list:
         goToBookmarks();
         break;
@@ -915,6 +930,117 @@ public class MainActivity extends BaseActivity implements WebViewCallback,
     return super.onOptionsItemSelected(item);
   }
 
+  /** Dialog to take user confirmation before deleting all notes */
+  private void showClearAllNotesDialog() {
+
+    AlertDialog.Builder builder;
+    if (sharedPreferenceUtil != null && sharedPreferenceUtil.nightMode()) { // Night Mode support
+      builder = new AlertDialog.Builder(this, R.style.AppTheme_Dialog_Night);
+    } else {
+      builder = new AlertDialog.Builder(this);
+    }
+
+    builder.setMessage(R.string.delete_notes_confirmation_msg)
+        .setNegativeButton(android.R.string.cancel, null) // Do nothing for 'Cancel' button
+        .setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
+          @Override
+          public void onClick(DialogInterface dialog, int which) {
+            clearAllNotes();
+          }
+        })
+        .show();
+  }
+
+  /** Method to delete all user notes */
+  private void clearAllNotes() {
+
+    boolean result = true; // Result of all delete() calls is &&-ed to this variable
+
+    if(AddNoteDialog.isExternalStorageWritable()) {
+      if(ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
+        Log.d("MainActivity", "WRITE_EXTERNAL_STORAGE permission not granted");
+        showToast(R.string.ext_storage_permission_not_granted, Toast.LENGTH_LONG);
+        return;
+      }
+
+      // TODO: Replace below code with Kotlin's deleteRecursively() method
+
+      File notesDirectory = new File(NOTES_DIRECTORY);
+      File[] filesInNotesDirectory = notesDirectory.listFiles();
+
+      if(filesInNotesDirectory == null) { // Notes folder doesn't exist
+        showToast(R.string.notes_deletion_none_found, Toast.LENGTH_LONG);
+        return;
+      }
+
+      for(File wikiFileDirectory : filesInNotesDirectory) {
+        if(wikiFileDirectory.isDirectory()) {
+          File[] filesInWikiDirectory = wikiFileDirectory.listFiles();
+
+          for(File noteFile : filesInWikiDirectory) {
+            if(noteFile.isFile()) {
+              result = result && noteFile.delete();
+            }
+          }
+        }
+
+        result = result && wikiFileDirectory.delete(); // Wiki specific notes directory deleted
+      }
+
+      result = result && notesDirectory.delete(); // "{External Storage}/Kiwix/Notes" directory deleted
+    }
+
+    if(result) {
+      showToast(R.string.notes_deletion_successful, Toast.LENGTH_SHORT);
+    } else {
+      showToast(R.string.notes_deletion_unsuccessful, Toast.LENGTH_SHORT);
+    }
+  }
+
+  /** Creates the full screen AddNoteDialog, which is a DialogFragment */
+  private void showAddNoteDialog() {
+    FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
+    Fragment previousInstance = getSupportFragmentManager().findFragmentByTag(AddNoteDialog.TAG);
+
+    // To prevent multiple instances of the DialogFragment
+    if(previousInstance == null) {
+      /* Since the DialogFragment is never added to the back-stack, so findFragmentByTag()
+      *  returning null means that the AddNoteDialog is currently not on display (as doesn't exist)
+      **/
+      AddNoteDialog dialogFragment = new AddNoteDialog(sharedPreferenceUtil);
+      dialogFragment.show(fragmentTransaction, AddNoteDialog.TAG); // For DialogFragments, show() handles the fragment commit and display
+    }
+  }
+
+  private boolean requestExternalStorageWritePermissionForNotes() {
+    if(Build.VERSION.SDK_INT >= 23) { // For Marshmallow & higher API levels
+
+      if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
+        return true;
+
+      } else {
+        if(shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
+          /* shouldShowRequestPermissionRationale() returns false when:
+           *  1) User has previously checked on "Don't ask me again", and/or
+           *  2) Permission has been disabled on device
+           */
+          showToast(R.string.ext_storage_permission_rationale_add_note, Toast.LENGTH_LONG);
+        }
+
+        requestPermissions(new String[] {Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_WRITE_STORAGE_PERMISSION_ADD_NOTE);
+      }
+
+    } else { // For Android versions below Marshmallow 6.0 (API 23)
+      return true; // As already requested at install time
+    }
+
+    return false;
+  }
+
+  private void showToast(int stringResource, int duration) {
+    Toast.makeText(this, stringResource, duration).show();
+  }
+
   @SuppressWarnings("SameReturnValue")
   @OnLongClick(R.id.bottom_toolbar_bookmark)
   boolean goToBookmarks() {
@@ -1084,6 +1210,20 @@ public class MainActivity extends BaseActivity implements WebViewCallback,
                 startActivity(intent);
               }).show();
         }
+        break;
+      }
+
+      case REQUEST_WRITE_STORAGE_PERMISSION_ADD_NOTE: {
+
+        if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+          // Successfully granted permission, so opening the note keeper
+          showAddNoteDialog();
+
+        } else {
+          Toast.makeText(getApplicationContext(), getString(R.string.ext_storage_write_permission_denied_add_note), Toast.LENGTH_LONG);
+        }
+
+        break;
       }
     }
   }

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

@@ -17,6 +17,8 @@
  */
 package org.kiwix.kiwixmobile.utils;
 
+import android.os.Environment;
+
 import org.kiwix.kiwixmobile.BuildConfig;
 
 public final class Constants {
@@ -30,6 +32,12 @@ public final class Constants {
 
   public static final int REQUEST_STORAGE_PERMISSION = 1;
 
+  public static final int REQUEST_READ_STORAGE_PERMISSION = 2;
+
+  public static final int REQUEST_WRITE_STORAGE_PERMISSION_ADD_NOTE = 3;
+
+  public static final int REQUEST_HISTORY_ITEM_CHOSEN = 99;
+
   public static final int REQUEST_FILE_SELECT = 1234;
 
   public static final int REQUEST_PREFERENCES = 1235;
@@ -130,4 +138,7 @@ public final class Constants {
   public static final String OLD_PROVIDER_DOMAIN = "org.kiwix.zim.base";
 
   public static final String NEW_PROVIDER_DOMAIN = BuildConfig.APPLICATION_ID + ".zim.base";
+
+  // Path Constants
+  public static final String NOTES_DIRECTORY = Environment.getExternalStorageDirectory() + "/Kiwix/Notes/";
 }

app/src/main/res/drawable/ic_add_note.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#FFFFFF"
+      android:pathData="M3,18h12v-2L3,16v2zM3,6v2h18L21,6L3,6zM3,13h18v-2L3,11v2z"/>
+</vector>

app/src/main/res/drawable/ic_baseline_delete_sweep_24px.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="M15,16h4v2h-4zM15,8h7v2h-7zM15,12h6v2h-6zM3,18c0,1.1 0.9,2 2,2h6c1.1,0 2,-0.9 2,-2L13,8L3,8v10zM14,5h-3l-1,-1L6,4L5,5L2,5v2h12z"/>
+</vector>

app/src/main/res/drawable/ic_close_white_24dp.xml

@@ -1,6 +1,6 @@
 <vector xmlns:android="http://schemas.android.com/apk/res/android"
     android:height="24dp"
-    android:tint="#000000"
+    android:tint="#ffffff"
     android:viewportHeight="24.0"
     android:viewportWidth="24.0"
     android:width="24dp">

app/src/main/res/drawable/ic_save.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#ffffff"
+      android:pathData="M17,3L5,3c-1.11,0 -2,0.9 -2,2v14c0,1.1 0.89,2 2,2h14c1.1,0 2,-0.9 2,-2L21,7l-4,-4zM12,19c-1.66,0 -3,-1.34 -3,-3s1.34,-3 3,-3 3,1.34 3,3 -1.34,3 -3,3zM15,9L5,9L5,5h10v4z"/>
+</vector>

app/src/main/res/layout/dialog_add_note.xml

@@ -0,0 +1,77 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="@android:color/transparent">
+
+  <com.google.android.material.appbar.AppBarLayout
+      android:id="@+id/app_bar_add_note_dialog"
+      android:layout_width="match_parent"
+      android:layout_height="wrap_content"
+      app:layout_constraintTop_toTopOf="parent"
+      app:layout_constraintLeft_toLeftOf="parent"
+      app:layout_constraintRight_toRightOf="parent">
+
+    <androidx.appcompat.widget.Toolbar
+        android:id="@+id/add_note_toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content">
+    </androidx.appcompat.widget.Toolbar>
+
+  </com.google.android.material.appbar.AppBarLayout>
+
+  <ScrollView
+      android:layout_width="0dp"
+      android:layout_height="0dp"
+      app:layout_constraintTop_toBottomOf="@id/app_bar_add_note_dialog"
+      app:layout_constraintBottom_toBottomOf="parent"
+      app:layout_constraintLeft_toLeftOf="parent"
+      app:layout_constraintRight_toRightOf="parent">
+
+    <LinearLayout
+        android:orientation="vertical"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent">
+
+      <TextView
+          android:id="@+id/add_note_text_view"
+          android:layout_width="match_parent"
+          android:layout_height="wrap_content"
+          android:maxLines="1"
+          android:background="@android:color/transparent"
+          android:hint="@string/wiki_article_title"
+          android:textAppearance="@style/TextAppearance.MaterialComponents.Headline5"
+          android:paddingTop="10dp"
+          android:paddingLeft="20dp"
+          android:paddingRight="20dp"/>
+
+      <View
+          android:layout_width="match_parent"
+          android:layout_height="1dp"
+          android:layout_marginLeft="15dp"
+          android:layout_marginTop="5dp"
+          android:layout_marginBottom="5dp"
+          android:layout_marginRight="15dp"
+          android:background="#000000"/>
+
+      <EditText
+          android:id="@+id/add_note_edit_text"
+          android:layout_width="match_parent"
+          android:layout_height="wrap_content"
+          android:paddingTop="5dp"
+          android:paddingBottom="10dp"
+          android:paddingLeft="20dp"
+          android:paddingRight="20dp"
+          android:inputType="textMultiLine|textCapSentences|textAutoCorrect"
+          android:minLines="6"
+          android:gravity="top|left"
+          android:textAppearance="@style/TextAppearance.MaterialComponents.Body1"
+          android:scrollbars="vertical"
+          android:background="@android:color/transparent"
+          android:hint="@string/note"/>
+
+    </LinearLayout>
+  </ScrollView>
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/menu/menu_add_note_dialog.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+  <item android:id="@+id/share_note"
+      android:icon="@drawable/baseline_share_24"
+      android:title="@string/share"
+      app:showAsAction="always"/>
+
+  <item android:id="@+id/save_note"
+    android:icon="@drawable/ic_save"
+    android:title="@string/save"
+    app:showAsAction="always"/>
+
+</menu>

app/src/main/res/menu/menu_main.xml

@@ -14,6 +14,18 @@
       app:actionLayout="@layout/ic_tab_switcher"
       app:showAsAction="always"/>
 
+  <item
+    android:id="@+id/menu_add_note"
+    android:title="@string/add_note"
+    android:icon="@drawable/ic_add_note"
+    app:showAsAction="always"/>
+
+  <item
+    android:id="@+id/menu_clear_notes"
+    android:title="@string/clear_all_notes"
+    android:icon="@drawable/ic_baseline_delete_sweep_24px"
+    app:showAsAction="ifRoom"/>
+
   <item
       android:id="@+id/menu_new_tab"
       android:title="@string/new_tab"

app/src/main/res/values/strings.xml

@@ -264,4 +264,22 @@
   <string name="failed_unhandled_http_code">Unknown HTTP code received</string>
   <string name="failed_unknown">Unknown</string>
   <string name="failed_http_code">HTTP code %s</string>
-</resources>
+  <string name="add_note">Add Note</string>
+  <string name="save">Save</string>
+  <string name="note">Note</string>
+  <string name="wiki_article_title">Wiki Article Title</string>
+  <string name="ext_storage_permission_rationale_add_note">Storage access is required for Notes</string>
+  <string name="ext_storage_write_permission_denied_add_note">Notes can\'t be used without access to storage</string>
+  <string name="note_save_unsuccessful">Note save unsuccessful</string>
+  <string name="note_save_successful">Note saved</string>
+  <string name="note_save_error_storage_not_writable">Error saving note: Storage not writable</string>
+  <string name="note_share_error_file_missing">Note file doesn\'t exist</string>
+  <string name="note_share_app_chooser_title">Share note file with:</string>
+  <string name="confirmation_alert_dialog_message">Discard unsaved changes?</string>
+  <string name="clear_all_notes">Clear All Notes</string>
+  <string name="delete_notes_confirmation_msg">Delete all notes?</string>
+  <string name="ext_storage_permission_not_granted">Error: Storage permissions not granted</string>
+  <string name="notes_deletion_none_found">No notes found for deletion</string>
+  <string name="notes_deletion_successful">Entire notes folder deleted</string>
+  <string name="notes_deletion_unsuccessful">Some files not deleted</string>
+</resources>

app/src/main/res/values/styles.xml

@@ -129,5 +129,29 @@
   <style name="NeutralButtonStyle" parent="Widget.AppCompat.Button.ButtonBar.AlertDialog">
     <item name="android:textColor">@color/accent</item>
   </style>
-</resources>
 
+  <style name="AddNoteDialogStyle" parent="Theme.AppCompat.Dialog">
+    <item name="android:windowNoTitle">true</item>
+    <item name="colorPrimaryDark">@color/primary_dark</item>
+    <item name="colorPrimary">@color/primary</item>
+    <item name="android:textColor">#000000</item>
+    <item name="android:editTextColor">#000000</item>
+    <item name="android:textColorHint">@color/textDarkTertiary</item>
+    <item name="android:windowFullscreen">false</item>
+    <item name="android:windowIsFloating">false</item>
+    <item name="android:windowBackground">@color/white</item>
+  </style>
+
+  <style name="AddNoteDialogStyle.Night" parent="Theme.AppCompat.Dialog">
+    <item name="android:windowNoTitle">true</item>
+    <item name="colorPrimaryDark">@color/primary_dark</item>
+    <item name="colorPrimary">@color/primary</item>
+    <item name="android:textColor">#ffffff</item>
+    <item name="android:editTextColor">#ffffff</item>
+    <item name="android:textColorHint">@color/grey</item>
+    <item name="android:windowFullscreen">false</item>
+    <item name="android:windowIsFloating">false</item>
+    <item name="android:windowBackground">@color/cardview_dark_background</item>
+  </style>
+
+</resources>