Let devs intercept onChanged events and control when to update their adapter

app/src/main/java/com/firebase/uidemo/database/ChatActivity.java

@@ -14,6 +14,7 @@
 
 package com.firebase.uidemo.database;
 
+import android.content.Context;
 import android.graphics.PorterDuff;
 import android.graphics.drawable.GradientDrawable;
 import android.graphics.drawable.RotateDrawable;
@@ -37,6 +38,7 @@
 import com.firebase.ui.database.FirebaseRecyclerAdapter;
 import com.firebase.uidemo.R;
 import com.google.android.gms.tasks.OnCompleteListener;
+import com.google.android.gms.tasks.OnSuccessListener;
 import com.google.android.gms.tasks.Task;
 import com.google.firebase.auth.AuthResult;
 import com.google.firebase.auth.FirebaseAuth;
@@ -86,9 +88,9 @@ public void onClick(View v) {
                 Chat chat = new Chat(name, mMessageEdit.getText().toString(), uid);
                 mChatRef.push().setValue(chat, new DatabaseReference.CompletionListener() {
                     @Override
-                    public void onComplete(DatabaseError databaseError, DatabaseReference reference) {
-                        if (databaseError != null) {
-                            Log.e(TAG, "Failed to write message", databaseError.toException());
+                    public void onComplete(DatabaseError error, DatabaseReference reference) {
+                        if (error != null) {
+                            Log.e(TAG, "Failed to write message", error.toException());
                         }
                     }
                 });
@@ -97,11 +99,10 @@ public void onComplete(DatabaseError databaseError, DatabaseReference reference)
             }
         });
 
-        mMessages = (RecyclerView) findViewById(R.id.messagesList);
-
         mManager = new LinearLayoutManager(this);
         mManager.setReverseLayout(false);
 
+        mMessages = (RecyclerView) findViewById(R.id.messagesList);
         mMessages.setHasFixedSize(false);
         mMessages.setLayoutManager(mManager);
     }
@@ -145,7 +146,6 @@ private void attachRecyclerViewAdapter() {
         Query lastFifty = mChatRef.limitToLast(50);
         mRecyclerViewAdapter = new FirebaseRecyclerAdapter<Chat, ChatHolder>(
                 Chat.class, R.layout.message, ChatHolder.class, lastFifty) {
-
             @Override
             public void populateViewHolder(ChatHolder chatView, Chat chat, int position) {
                 chatView.setName(chat.getName());
@@ -180,20 +180,13 @@ public void onItemRangeInserted(int positionStart, int itemCount) {
     private void signInAnonymously() {
         Toast.makeText(this, "Signing in...", Toast.LENGTH_SHORT).show();
         mAuth.signInAnonymously()
-                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
+                .addOnSuccessListener(this, new OnSuccessListener<AuthResult>() {
                     @Override
-                    public void onComplete(@NonNull Task<AuthResult> task) {
-                        Log.d(TAG, "signInAnonymously:onComplete:" + task.isSuccessful());
-                        if (task.isSuccessful()) {
-                            Toast.makeText(ChatActivity.this, "Signed In",
-                                    Toast.LENGTH_SHORT).show();
-                            attachRecyclerViewAdapter();
-                        } else {
-                            Toast.makeText(ChatActivity.this, "Sign In Failed",
-                                    Toast.LENGTH_SHORT).show();
-                        }
+                    public void onSuccess(AuthResult result) {
+                        attachRecyclerViewAdapter();
                     }
-                });
+                })
+                .addOnCompleteListener(new SignInResultNotifier(this));
     }
 
     public boolean isSignedIn() {
@@ -297,4 +290,24 @@ public void setText(String text) {
             mTextField.setText(text);
         }
     }
+
+    /**
+     * Notifies the user of sign in successes or failures beyond the lifecycle of an activity.
+     */
+    private static class SignInResultNotifier implements OnCompleteListener<AuthResult> {
+        private Context mContext;
+
+        public SignInResultNotifier(Context context) {
+            mContext = context.getApplicationContext();
+        }
+
+        @Override
+        public void onComplete(@NonNull Task<AuthResult> task) {
+            if (task.isSuccessful()) {
+                Toast.makeText(mContext, R.string.signed_in, Toast.LENGTH_SHORT).show();
+            } else {
+                Toast.makeText(mContext, R.string.sign_in_failed, Toast.LENGTH_SHORT).show();
+            }
+        }
+    }
 }

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

@@ -67,4 +67,6 @@
 
     <!-- strings for Auth UI demo activities -->
     <string name="start_chatting">No messages. Start chatting at the bottom!</string>
+    <string name="sign_in_failed">Sign In Failed</string>
+    <string name="signed_in">Signed In</string>
 </resources>

database/README.md

@@ -86,8 +86,8 @@ ref.limitToLast(5).addValueEventListener(new ValueEventListener() {
         }
     }
     @Override
-    public void onCancelled(DatabaseError firebaseError) {
-        Log.e("Chat", "The read failed: " + firebaseError.getText());
+    public void onCancelled(DatabaseError error) {
+        Log.e("Chat", "The read failed: " + error.getText());
     }
 });
 ```

database/src/androidTest/java/com/firebase/ui/database/TestUtils.java

@@ -37,19 +37,19 @@ public static void runAndWaitUntil(FirebaseArray array,
                                        Runnable task,
                                        Callable<Boolean> done) throws InterruptedException {
         final Semaphore semaphore = new Semaphore(0);
-        array.setOnChangedListener(new FirebaseArray.OnChangedListener() {
 
+        array.setOnChangedListener(new ChangeEventListener() {
             @Override
-            public void onChildChanged(EventType type, int index, int oldIndex) {
+            public void onChildChanged(ChangeEventListener.EventType type, int index, int oldIndex) {
                 semaphore.release();
             }
 
             @Override
             public void onDataChanged() {}
 
             @Override
-            public void onCancelled(DatabaseError databaseError) {
-                throw new IllegalStateException(databaseError.toException());
+            public void onCancelled(DatabaseError error) {
+                throw new IllegalStateException(error.toException());
             }
         });
         task.run();

database/src/main/java/com/firebase/ui/database/ChangeEventListener.java

@@ -0,0 +1,65 @@
+package com.firebase.ui.database;
+
+import com.google.firebase.database.ChildEventListener;
+import com.google.firebase.database.DataSnapshot;
+import com.google.firebase.database.DatabaseError;
+
+public interface ChangeEventListener {
+    /**
+     * The type of event received when a child has been updated.
+     */
+    enum EventType {
+        /**
+         * An onChildAdded event was received.
+         *
+         * @see ChildEventListener#onChildAdded(DataSnapshot, String)
+         */
+        ADDED,
+        /**
+         * An onChildChanged event was received.
+         *
+         * @see ChildEventListener#onChildChanged(DataSnapshot, String)
+         */
+        CHANGED,
+        /**
+         * An onChildRemoved event was received.
+         *
+         * @see ChildEventListener#onChildRemoved(DataSnapshot)
+         */
+        REMOVED,
+        /**
+         * An onChildMoved event was received.
+         *
+         * @see ChildEventListener#onChildMoved(DataSnapshot, String)
+         */
+        MOVED
+    }
+
+    /**
+     * A callback for when a child has changed in FirebaseArray.
+     *
+     * @param type     The type of event received
+     * @param index    The index at which the change occurred
+     * @param oldIndex If {@code type} is a moved event, the previous index of the moved child.
+     *                 For any other event, {@code oldIndex} will be -1.
+     */
+    void onChildChanged(EventType type, int index, int oldIndex);
+
+    /** This method will be triggered each time updates from the database have been completely processed.
+     * So the first time this method is called, the initial data has been loaded - including the case
+     * when no data at all is available. Each next time the method is called, a complete update (potentially
+     * consisting of updates to multiple child items) has been completed.
+     * <p>
+     * You would typically override this method to hide a loading indicator (after the initial load) or
+     * to complete a batch update to a UI element.
+     */
+    void onDataChanged();
+
+    /**
+     * This method will be triggered in the event that this listener either failed at the server,
+     * or is removed as a result of the security and Firebase Database rules.
+     *
+     * @param error A description of the error that occurred
+     */
+    void onCancelled(DatabaseError error);
+}

database/src/main/java/com/firebase/ui/database/FirebaseArray.java

@@ -27,19 +27,8 @@
  * This class implements an array-like collection on top of a Firebase location.
  */
 class FirebaseArray implements ChildEventListener, ValueEventListener {
-    public interface OnChangedListener {
-        enum EventType {ADDED, CHANGED, REMOVED, MOVED}
-
-        void onChildChanged(EventType type, int index, int oldIndex);
-
-        void onDataChanged();
-
-        void onCancelled(DatabaseError databaseError);
-
-    }
-
     private Query mQuery;
-    private OnChangedListener mListener;
+    private ChangeEventListener mListener;
     private List<DataSnapshot> mSnapshots = new ArrayList<>();
 
     public FirebaseArray(Query ref) {
@@ -80,21 +69,21 @@ public void onChildAdded(DataSnapshot snapshot, String previousChildKey) {
             index = getIndexForKey(previousChildKey) + 1;
         }
         mSnapshots.add(index, snapshot);
-        notifyChangedListeners(OnChangedListener.EventType.ADDED, index);
+        notifyChangedListeners(ChangeEventListener.EventType.ADDED, index);
     }
 
     @Override
     public void onChildChanged(DataSnapshot snapshot, String previousChildKey) {
         int index = getIndexForKey(snapshot.getKey());
         mSnapshots.set(index, snapshot);
-        notifyChangedListeners(OnChangedListener.EventType.CHANGED, index);
+        notifyChangedListeners(ChangeEventListener.EventType.CHANGED, index);
     }
 
     @Override
     public void onChildRemoved(DataSnapshot snapshot) {
         int index = getIndexForKey(snapshot.getKey());
         mSnapshots.remove(index);
-        notifyChangedListeners(OnChangedListener.EventType.REMOVED, index);
+        notifyChangedListeners(ChangeEventListener.EventType.REMOVED, index);
     }
 
     @Override
@@ -103,7 +92,7 @@ public void onChildMoved(DataSnapshot snapshot, String previousChildKey) {
         mSnapshots.remove(oldIndex);
         int newIndex = previousChildKey == null ? 0 : (getIndexForKey(previousChildKey) + 1);
         mSnapshots.add(newIndex, snapshot);
-        notifyChangedListeners(OnChangedListener.EventType.MOVED, newIndex, oldIndex);
+        notifyChangedListeners(ChangeEventListener.EventType.MOVED, newIndex, oldIndex);
     }
 
     @Override
@@ -116,23 +105,23 @@ public void onCancelled(DatabaseError error) {
         notifyCancelledListeners(error);
     }
 
-    public void setOnChangedListener(OnChangedListener listener) {
+    public void setOnChangedListener(ChangeEventListener listener) {
         mListener = listener;
     }
 
-    protected void notifyChangedListeners(OnChangedListener.EventType type, int index) {
+    protected void notifyChangedListeners(ChangeEventListener.EventType type, int index) {
         notifyChangedListeners(type, index, -1);
     }
 
-    protected void notifyChangedListeners(OnChangedListener.EventType type, int index, int oldIndex) {
+    protected void notifyChangedListeners(ChangeEventListener.EventType type, int index, int oldIndex) {
         if (mListener != null) {
             mListener.onChildChanged(type, index, oldIndex);
         }
     }
 
-    protected void notifyCancelledListeners(DatabaseError databaseError) {
+    protected void notifyCancelledListeners(DatabaseError error) {
         if (mListener != null) {
-            mListener.onCancelled(databaseError);
+            mListener.onCancelled(error);
         }
     }
 }

database/src/main/java/com/firebase/ui/database/FirebaseIndexArray.java

@@ -32,7 +32,7 @@ class FirebaseIndexArray extends FirebaseArray {
     private static final String TAG = FirebaseIndexArray.class.getSimpleName();
 
     private Query mQuery;
-    private OnChangedListener mListener;
+    private ChangeEventListener mListener;
     private Map<Query, ValueEventListener> mRefs = new HashMap<>();
     private List<DataSnapshot> mDataSnapshots = new ArrayList<>();
 
@@ -107,7 +107,7 @@ public void onChildRemoved(DataSnapshot keySnapshot) {
 
         if (isMatch(index, key)) {
             mDataSnapshots.remove(index);
-            notifyChangedListeners(OnChangedListener.EventType.REMOVED, index);
+            notifyChangedListeners(ChangeEventListener.EventType.REMOVED, index);
         }
     }
 
@@ -124,7 +124,7 @@ public void onChildMoved(DataSnapshot keySnapshot, String previousChildKey) {
             DataSnapshot snapshot = mDataSnapshots.remove(oldIndex);
             int newIndex = getIndexForKey(key);
             mDataSnapshots.add(newIndex, snapshot);
-            notifyChangedListeners(OnChangedListener.EventType.MOVED, newIndex, oldIndex);
+            notifyChangedListeners(ChangeEventListener.EventType.MOVED, newIndex, oldIndex);
         }
     }
 
@@ -135,7 +135,7 @@ public void onCancelled(DatabaseError error) {
     }
 
     @Override
-    public void setOnChangedListener(OnChangedListener listener) {
+    public void setOnChangedListener(ChangeEventListener listener) {
         super.setOnChangedListener(listener);
         mListener = listener;
     }
@@ -149,15 +149,15 @@ public void onDataChange(DataSnapshot snapshot) {
             if (snapshot.getValue() != null) {
                 if (!isMatch(index, key)) {
                     mDataSnapshots.add(index, snapshot);
-                    notifyChangedListeners(OnChangedListener.EventType.ADDED, index);
+                    notifyChangedListeners(ChangeEventListener.EventType.ADDED, index);
                 } else {
                     mDataSnapshots.set(index, snapshot);
-                    notifyChangedListeners(OnChangedListener.EventType.CHANGED, index);
+                    notifyChangedListeners(ChangeEventListener.EventType.CHANGED, index);
                 }
             } else {
                 if (isMatch(index, key)) {
                     mDataSnapshots.remove(index);
-                    notifyChangedListeners(OnChangedListener.EventType.REMOVED, index);
+                    notifyChangedListeners(ChangeEventListener.EventType.REMOVED, index);
                 } else {
                     Log.w(TAG, "Key not found at ref: " + snapshot.getRef());
                 }