Fix app crashing when receiving multiple push notifications

android/src/main/java/io/ably/flutter/plugin/push/FirebaseMessagingReceiver.java

@@ -26,24 +26,37 @@ public class FirebaseMessagingReceiver extends BroadcastReceiver {
   @Nullable
   private PendingResult asyncProcessingPendingResult = null;
 
+  @Nullable
+  private BackgroundMessageProcessingCompleteReceiver backgroundMessageProcessingCompleteReceiver = null;
+
   @Override
   public void onReceive(Context context, Intent intent) {
-    final Boolean isApplicationInForeground = isApplicationInForeground(context);
-    final RemoteMessage message = new RemoteMessage(intent.getExtras());
-    final RemoteMessage.Notification notification = message.getNotification();
-    final boolean isDataMessage = !message.getData().isEmpty();
-    if (!isDataMessage) {
-      // Do not send a RemoteMessage without any data, to be consistent with iOS: 
-      // it doesn't call `didReceiveRemoteNotification` in this case.
-      Log.d(TAG, "Not sending message to dart side because it is a notification message without any data.");
-      return;
-    }
+    setupFlutterApplicationProcessingCompletionReceiver(context);
+    sendMessageToFlutterApplication(context, intent);
+  }
+
+  /**
+   * Launches a broadcast receiver ([BackgroundMessageProcessingCompleteReceiver]) so that the
+   * enclosing receiver (FirebaseMessagingReceiver), can be informed when the Flutter
+   * application completes. The Flutter application also has a receiver
+   * (PushMessagingEventHandlers.BroadcastReceiver) to listen to messages from this receiver
+   * (FirebaseMessagingReceiver).
+   */
+  private void setupFlutterApplicationProcessingCompletionReceiver(Context context) {
+    // Wait for Flutter application to process message
     // At the end of the receiver's execution time (and user's application processing the message)
-    // , Firebase messaging library will automatically create a notification. 
+    // , Firebase messaging library will automatically create a notification.
     // On iOS, the notification may be shown before the  message is processed by the application.
     // goAsync() also increases the execution time from 10s/ 20s (depending on API level) to 30s
-    new BackgroundMessageProcessingCompleteReceiver(context);
-    asyncProcessingPendingResult = goAsync();
+    if (backgroundMessageProcessingCompleteReceiver == null) {
+      backgroundMessageProcessingCompleteReceiver = new BackgroundMessageProcessingCompleteReceiver(context);
+      asyncProcessingPendingResult = goAsync();
+    }
+  }
+
+  private void sendMessageToFlutterApplication(Context context, Intent intent) {
+    final RemoteMessage message = new RemoteMessage(intent.getExtras());
+    final Boolean isApplicationInForeground = isApplicationInForeground(context);
 
     if (isApplicationInForeground) {
       // Send message to Dart side app already running
@@ -59,9 +72,10 @@ public void onReceive(Context context, Intent intent) {
       // No existing Flutter Activity is running, create a FlutterEngine and pass it the RemoteMessage
       new PushBackgroundIsolateRunner(context, this, message);
     }
+
   }
 
-  Boolean isApplicationInForeground(final Context context) {
+  private Boolean isApplicationInForeground(final Context context) {
     final ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
     // This only shows processes for the current android app.
     final List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
@@ -80,6 +94,9 @@ Boolean isApplicationInForeground(final Context context) {
     return false;
   }
 
+  /**
+   * A dynamic broadcast receiver registered to listen to a `PUSH_ON_BACKGROUND_MESSAGE_PROCESSING_COMPLETE`
+   */
   class BackgroundMessageProcessingCompleteReceiver extends BroadcastReceiver {
     BackgroundMessageProcessingCompleteReceiver(final Context context) {
       final IntentFilter filter = new IntentFilter();
@@ -89,6 +106,11 @@ class BackgroundMessageProcessingCompleteReceiver extends BroadcastReceiver {
 
     @Override
     public void onReceive(Context context, Intent intent) {
+      if (backgroundMessageProcessingCompleteReceiver != null) {
+        LocalBroadcastManager.getInstance(context).unregisterReceiver(backgroundMessageProcessingCompleteReceiver);
+        backgroundMessageProcessingCompleteReceiver = null;
+      }
+
       String action = intent.getAction();
       if (action.equals(PUSH_ON_BACKGROUND_MESSAGE_PROCESSING_COMPLETE)) {
         finish();

android/src/main/java/io/ably/flutter/plugin/push/PushMessagingEventHandlers.java

@@ -51,7 +51,6 @@ private void register(Context context) {
     @Override
     public void onReceive(Context context, Intent intent) {
       String action = intent.getAction();
-      Bundle intentExtras = intent.getExtras();
       RemoteMessage message = new RemoteMessage(intent.getExtras());
       switch (action) {
         case PUSH_ON_MESSAGE_RECEIVED:

example/lib/main.dart

@@ -142,6 +142,7 @@ class _MyAppState extends State<MyApp> {
 
   Future<void> createAblyRest() async {
     final clientOptions = ably.ClientOptions.fromKey(_apiKey)
+      ..clientId = Constants.clientId
       ..logLevel = ably.LogLevel.verbose
       ..logHandler = ({msg, exception}) {
         print('Custom logger :: $msg $exception');