Always remove TextWatcher when finished with it.

app/src/main/java/fr/free/nrw/commons/auth/LoginActivity.java

@@ -30,9 +30,10 @@ public class LoginActivity extends AccountAuthenticatorActivity {
 
     private Button loginButton;
     private EditText usernameEdit;
-    EditText passwordEdit;
+    private EditText passwordEdit;
-    EditText twoFactorEdit;
+    private EditText twoFactorEdit;
     ProgressDialog progressDialog;
+    private LoginTextWatcher textWatcher = new LoginTextWatcher();
 
     private CommonsApplication app;
 
@@ -53,10 +54,9 @@ public class LoginActivity extends AccountAuthenticatorActivity {
 
         prefs = getSharedPreferences("fr.free.nrw.commons", MODE_PRIVATE);
 
-        TextWatcher loginEnabler = newLoginTextWatcher();
+        usernameEdit.addTextChangedListener(textWatcher);
-        usernameEdit.addTextChangedListener(loginEnabler);
+        passwordEdit.addTextChangedListener(textWatcher);
-        passwordEdit.addTextChangedListener(loginEnabler);
+        twoFactorEdit.addTextChangedListener(textWatcher);
-        twoFactorEdit.addTextChangedListener(loginEnabler);
         passwordEdit.setOnEditorActionListener( newLoginInputActionListener() );
 
         loginButton.setOnClickListener(new View.OnClickListener() {
@@ -71,27 +71,24 @@ public class LoginActivity extends AccountAuthenticatorActivity {
         });
     }
 
-    private TextWatcher newLoginTextWatcher() {
+    private class LoginTextWatcher implements TextWatcher {
-        return new TextWatcher() {
         @Override
-            public void beforeTextChanged(CharSequence charSequence, int start, int count, int after) { }
+        public void beforeTextChanged(CharSequence charSequence, int start, int count, int after) {
+        }
 
         @Override
-            public void onTextChanged(CharSequence charSequence, int start, int count, int after) { }
+        public void onTextChanged(CharSequence charSequence, int start, int count, int after) {
+        }
 
         @Override
         public void afterTextChanged(Editable editable) {
-                if(
+            if (usernameEdit.getText().length() != 0 && passwordEdit.getText().length() != 0 &&
-                        usernameEdit.getText().length() != 0 &&
+                    (BuildConfig.DEBUG || twoFactorEdit.getText().length() != 0 || twoFactorEdit.getVisibility() != View.VISIBLE)) {
-                                passwordEdit.getText().length() != 0 &&
-                                ( BuildConfig.DEBUG || twoFactorEdit.getText().length() != 0 || twoFactorEdit.getVisibility() != View.VISIBLE )
-                        ) {
                 loginButton.setEnabled(true);
             } else {
                 loginButton.setEnabled(false);
             }
         }
-        };
     }
 
     private TextView.OnEditorActionListener newLoginInputActionListener() {
@@ -138,6 +135,9 @@ public class LoginActivity extends AccountAuthenticatorActivity {
         } catch (Exception e) {
             e.printStackTrace();
         }
+        usernameEdit.removeTextChangedListener(textWatcher);
+        passwordEdit.removeTextChangedListener(textWatcher);
+        twoFactorEdit.removeTextChangedListener(textWatcher);
         super.onDestroy();
     }
 

app/src/main/java/fr/free/nrw/commons/category/CategorizationFragment.java

@@ -1,6 +1,5 @@
 package fr.free.nrw.commons.category;
 
-import android.app.Activity;
 import android.content.ContentProviderClient;
 import android.content.DialogInterface;
 import android.content.SharedPreferences;
@@ -58,6 +57,7 @@ public class CategorizationFragment extends Fragment {
     ProgressBar categoriesSearchInProgress;
     TextView categoriesNotFoundView;
     TextView categoriesSkip;
+    private CategoryTextWatcher textWatcher = new CategoryTextWatcher();
 
     CategoriesAdapter categoriesAdapter;
     ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(2);
@@ -442,21 +442,7 @@ public class CategorizationFragment extends Fragment {
             }
         });
 
-        categoriesFilter.addTextChangedListener(new TextWatcher() {
+        categoriesFilter.addTextChangedListener(textWatcher);
-            @Override
-            public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
-            }
-
-            @Override
-            public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
-                startUpdatingCategoryList();
-            }
-
-            @Override
-            public void afterTextChanged(Editable editable) {
-
-            }
-        });
 
         startUpdatingCategoryList();
 
@@ -469,14 +455,6 @@ public class CategorizationFragment extends Fragment {
         inflater.inflate(R.menu.fragment_categorization, menu);
     }
 
-    @Override
-    public void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        setHasOptionsMenu(true);
-        getActivity().setTitle(R.string.categories_activity_title);
-        client = getActivity().getContentResolver().acquireContentProviderClient(CategoryContentProvider.AUTHORITY);
-    }
-
     @Override
     public void onResume() {
         super.onResume();
@@ -498,6 +476,12 @@ public class CategorizationFragment extends Fragment {
         }
     }
 
+    @Override
+    public void onDestroyView() {
+        categoriesFilter.removeTextChangedListener(textWatcher);
+        super.onDestroyView();
+    }
+
     public void backButtonDialog() {
         AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
 
@@ -581,8 +565,27 @@ public class CategorizationFragment extends Fragment {
     }
 
     @Override
-    public void onAttach(Activity activity) {
+    public void onActivityCreated(Bundle savedInstanceState) {
-        super.onAttach(activity);
+        super.onActivityCreated(savedInstanceState);
-        onCategoriesSaveHandler = (OnCategoriesSaveHandler) activity;
+        setHasOptionsMenu(true);
+        onCategoriesSaveHandler = (OnCategoriesSaveHandler) getActivity();
+        getActivity().setTitle(R.string.categories_activity_title);
+        client = getActivity().getContentResolver().acquireContentProviderClient(CategoryContentProvider.AUTHORITY);
+    }
+
+    private class CategoryTextWatcher implements TextWatcher {
+        @Override
+        public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
+        }
+
+        @Override
+        public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
+            startUpdatingCategoryList();
+        }
+
+        @Override
+        public void afterTextChanged(Editable editable) {
+
+        }
     }
 }

app/src/main/java/fr/free/nrw/commons/upload/MultipleUploadListFragment.java

@@ -39,6 +39,7 @@ public class MultipleUploadListFragment extends Fragment {
     private GridView photosGrid;
     private PhotoDisplayAdapter photosAdapter;
     private EditText baseTitle;
+    private TitleTextWatcher textWatcher = new TitleTextWatcher();
 
     private Point photoSize;
     private MediaDetailPagerFragment.MediaDetailProvider detailProvider;
@@ -88,7 +89,6 @@ public class MultipleUploadListFragment extends Fragment {
                 holder = (UploadHolderView)view.getTag();
             }
 
-
             Contribution up = (Contribution)this.getItem(i);
 
             if(holder.imageUri == null || !holder.imageUri.equals(up.getLocalUri())) {
@@ -161,37 +161,16 @@ public class MultipleUploadListFragment extends Fragment {
         photoSize = calculatePicDimension(detailProvider.getTotalMediaCount());
         photosGrid.setColumnWidth(photoSize.x);
 
-        baseTitle.addTextChangedListener(new TextWatcher() {
+        baseTitle.addTextChangedListener(textWatcher);
-            @Override
-            public void beforeTextChanged(CharSequence charSequence, int i1, int i2, int i3) {
-
-            }
-
-            @Override
-            public void onTextChanged(CharSequence charSequence, int i1, int i2, int i3) {
-                for(int i = 0; i < detailProvider.getTotalMediaCount(); i++) {
-                    Contribution up = (Contribution) detailProvider.getMediaAtPosition(i);
-                    Boolean isDirty = (Boolean)up.getTag("isDirty");
-                    if(isDirty == null || !isDirty) {
-                        if(!TextUtils.isEmpty(charSequence)) {
-                            up.setFilename(charSequence.toString() + " - " + ((Integer)up.getTag("sequence") + 1));
-                        } else {
-                            up.setFilename("");
-                        }
-                    }
-                }
-                detailProvider.notifyDatasetChanged();
-            }
-
-            @Override
-            public void afterTextChanged(Editable editable) {
-
-            }
-        });
-
         return view;
     }
 
+    @Override
+    public void onDestroyView() {
+        baseTitle.removeTextChangedListener(textWatcher);
+        super.onDestroyView();
+    }
+
     @Override
     public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
         super.onCreateOptionsMenu(menu, inflater);
@@ -219,4 +198,29 @@ public class MultipleUploadListFragment extends Fragment {
         setHasOptionsMenu(true);
     }
 
+    private class TitleTextWatcher implements TextWatcher {
+        @Override
+        public void beforeTextChanged(CharSequence charSequence, int i1, int i2, int i3) {
+        }
+
+        @Override
+        public void onTextChanged(CharSequence charSequence, int i1, int i2, int i3) {
+            for(int i = 0; i < detailProvider.getTotalMediaCount(); i++) {
+                Contribution up = (Contribution) detailProvider.getMediaAtPosition(i);
+                Boolean isDirty = (Boolean)up.getTag("isDirty");
+                if(isDirty == null || !isDirty) {
+                    if(!TextUtils.isEmpty(charSequence)) {
+                        up.setFilename(charSequence.toString() + " - " + ((Integer)up.getTag("sequence") + 1));
+                    } else {
+                        up.setFilename("");
+                    }
+                }
+            }
+            detailProvider.notifyDatasetChanged();
+        }
+
+        @Override
+        public void afterTextChanged(Editable editable) {
+        }
+    }
 }

app/src/main/java/fr/free/nrw/commons/upload/SingleUploadFragment.java

@@ -1,6 +1,5 @@
 package fr.free.nrw.commons.upload;
 
-import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
@@ -53,6 +52,7 @@ public class SingleUploadFragment extends Fragment {
     @BindView(R.id.licenseSpinner) Spinner licenseSpinner;
 
     private OnUploadActionInitiated uploadActionInitiatedHandler;
+    private TitleTextWatcher textWatcher = new TitleTextWatcher();
 
     @Override
     public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
@@ -125,28 +125,19 @@ public class SingleUploadFragment extends Fragment {
         Timber.d("Position: %d %s", position, getString(Utils.licenseNameFor(license)));
         licenseSpinner.setSelection(position);
 
-        TextWatcher uploadEnabler = new TextWatcher() {
+        titleEdit.addTextChangedListener(textWatcher);
-            @Override
-            public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) { }
-
-            @Override
-            public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {}
-
-            @Override
-            public void afterTextChanged(Editable editable) {
-                if(getActivity() != null) {
-                    getActivity().invalidateOptionsMenu();
-                }
-            }
-        };
-
-        titleEdit.addTextChangedListener(uploadEnabler);
 
         setLicenseSummary(license);
 
         return rootView;
     }
 
+    @Override
+    public void onDestroyView() {
+        titleEdit.removeTextChangedListener(textWatcher);
+        super.onDestroyView();
+    }
+
     @OnItemSelected(R.id.licenseSpinner) void onLicenseSelected(AdapterView<?> parent, View view, int position, long id) {
         String licenseName = parent.getItemAtPosition(position).toString();
 
@@ -206,9 +197,10 @@ public class SingleUploadFragment extends Fragment {
     }
 
     @Override
-    public void onAttach(Activity activity) {
+    public void onActivityCreated(Bundle savedInstanceState) {
-        super.onAttach(activity);
+        super.onActivityCreated(savedInstanceState);
-        uploadActionInitiatedHandler = (OnUploadActionInitiated) activity;
+        setHasOptionsMenu(true);
+        uploadActionInitiatedHandler = (OnUploadActionInitiated) getActivity();
     }
 
     @Override
@@ -223,9 +215,18 @@ public class SingleUploadFragment extends Fragment {
         }
     }
 
+    private class TitleTextWatcher implements TextWatcher {
         @Override
-    public void onCreate(Bundle savedInstanceState) {
+        public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) { }
-        super.onCreate(savedInstanceState);
+
-        setHasOptionsMenu(true);
+        @Override
+        public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) { }
+
+        @Override
+        public void afterTextChanged(Editable editable) {
+            if(getActivity() != null) {
+                getActivity().invalidateOptionsMenu();
+            }
+        }
     }
 }