Merge pull request #215 from ably/bug/app-processes-is-null

0 Fix app crashing when app is not yet started on some devices

android/src/main/java/io/ably/flutter/plugin/AblyFlutterPlugin.java

@@ -10,8 +10,6 @@
 
 import com.google.firebase.messaging.RemoteMessage;
 
-import javax.crypto.Cipher;
-
 import io.ably.flutter.plugin.generated.PlatformConstants;
 import io.ably.flutter.plugin.push.RemoteMessageCallback;
 import io.ably.flutter.plugin.push.PushActivationEventHandlers;
@@ -74,7 +72,7 @@ private void setupChannels(BinaryMessenger messenger, Context applicationContext
         BackgroundMethodCallHandler backgroundMethodCallHandler = new BackgroundMethodCallHandler(messenger, codec);
         methodChannel.setMethodCallHandler(methodCallHandler);
         PushActivationEventHandlers.instantiate(applicationContext, methodChannel);
-        PushMessagingEventHandlers.instantiate(applicationContext, methodChannel);
+        PushMessagingEventHandlers.reset(applicationContext, methodChannel);
     }
 
     @Override

android/src/main/java/io/ably/flutter/plugin/AblyMethodCallHandler.java

@@ -18,7 +18,6 @@
 
 import io.ably.flutter.plugin.generated.PlatformConstants;
 import io.ably.flutter.plugin.push.PushActivationEventHandlers;
-import io.ably.flutter.plugin.push.PushBackgroundIsolateRunner;
 import io.ably.flutter.plugin.types.PlatformClientOptions;
 import io.ably.flutter.plugin.util.BiConsumer;
 import io.ably.lib.realtime.AblyRealtime;
@@ -102,7 +101,6 @@ public AblyMethodCallHandler(final MethodChannel channel,
     _map.put(PlatformConstants.PlatformMethod.pushListSubscriptions, this::pushListSubscriptions);
     _map.put(PlatformConstants.PlatformMethod.pushDevice, this::pushDevice);
     _map.put(PlatformConstants.PlatformMethod.pushNotificationTapLaunchedAppFromTerminated, this::pushNotificationTapLaunchedAppFromTerminated);
-    _map.put(PlatformConstants.PlatformMethod.pushSetOnBackgroundMessage, this::pushSetOnBackgroundMessage);
 
     // paginated results
     _map.put(PlatformConstants.PlatformMethod.nextPage, this::getNextPage);
@@ -740,11 +738,6 @@ private void pushNotificationTapLaunchedAppFromTerminated(@NonNull MethodCall ca
     remoteMessageFromUserTapLaunchesApp = null;
   }
 
-  private void pushSetOnBackgroundMessage(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
-    Long backgroundMessageHandlerHandle = (Long) call.arguments;
-    PushBackgroundIsolateRunner.setBackgroundMessageHandler(applicationContext, backgroundMessageHandlerHandle);
-  }
-
   private void getNextPage(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
     final AblyFlutterMessage message = (AblyFlutterMessage) call.arguments;
     this.<Integer>ablyDo(

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

@@ -1,8 +1,6 @@
 package io.ably.flutter.plugin.push;
 
 import static io.ably.flutter.plugin.push.PushMessagingEventHandlers.PUSH_ON_BACKGROUND_MESSAGE_PROCESSING_COMPLETE;
-import static io.ably.flutter.plugin.push.PushMessagingEventHandlers.PUSH_ON_BACKGROUND_MESSAGE_RECEIVED;
-import static io.ably.flutter.plugin.push.PushMessagingEventHandlers.PUSH_ON_MESSAGE_RECEIVED;
 
 import android.app.ActivityManager;
 import android.content.BroadcastReceiver;
@@ -11,11 +9,10 @@
 import android.content.IntentFilter;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.localbroadcastmanager.content.LocalBroadcastManager;
 
-import com.google.firebase.messaging.RemoteMessage;
-
 import java.util.List;
 
 import io.ably.flutter.plugin.AblyFlutterPlugin;
@@ -42,7 +39,7 @@ public void onReceive(Context context, Intent intent) {
    * (PushMessagingEventHandlers.BroadcastReceiver) to listen to messages from this receiver
    * (FirebaseMessagingReceiver).
    */
-  private void setupFlutterApplicationProcessingCompletionReceiver(Context context) {
+  private void setupFlutterApplicationProcessingCompletionReceiver(@NonNull final 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.
@@ -54,32 +51,30 @@ private void setupFlutterApplicationProcessingCompletionReceiver(Context context
     }
   }
 
-  private void sendMessageToFlutterApplication(Context context, Intent intent) {
-    final RemoteMessage message = new RemoteMessage(intent.getExtras());
+  private void sendMessageToFlutterApplication(@NonNull final Context context,
+                                               @NonNull final Intent intent) {
     final Boolean isApplicationInForeground = isApplicationInForeground(context);
 
     if (isApplicationInForeground) {
-      // Send message to Dart side app already running
-      final Intent onMessageReceivedIntent = new Intent(PUSH_ON_MESSAGE_RECEIVED);
-      onMessageReceivedIntent.putExtras(intent.getExtras());
-      LocalBroadcastManager.getInstance(context).sendBroadcast(onMessageReceivedIntent);
+      PushMessagingEventHandlers.sendMessageToFlutterApp(context, intent);
     } else if (AblyFlutterPlugin.isMainActivityRunning) {
-      // Flutter is already running, just send a background message to it.
-      final Intent onMessageReceivedIntent = new Intent(PUSH_ON_BACKGROUND_MESSAGE_RECEIVED);
-      onMessageReceivedIntent.putExtras(intent.getExtras());
-      LocalBroadcastManager.getInstance(context).sendBroadcast(onMessageReceivedIntent);
+      PushMessagingEventHandlers.sendBackgroundMessageToFlutterApp(context, intent);
     } else {
-      // No existing Flutter Activity is running, create a FlutterEngine and pass it the RemoteMessage
-      new PushBackgroundIsolateRunner(context, this, message);
+      new ManualFlutterApplicationRunner(context, this, intent);
     }
-
   }
 
-  private Boolean isApplicationInForeground(final Context context) {
+  private Boolean isApplicationInForeground(@NonNull 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();
 
+    if (appProcesses == null) {
+      // If no processes are running, appProcesses are null, not an empty list.
+      // The user's app is definitely not in the foreground if no processes are running.
+      return false;
+    }
+
     for (ActivityManager.RunningAppProcessInfo process : appProcesses) {
       // Importance is IMPORTANCE_SERVICE (not IMPORTANCE_FOREGROUND)
       //  - when app was terminated, or
@@ -98,7 +93,7 @@ private Boolean isApplicationInForeground(final Context context) {
    * A dynamic broadcast receiver registered to listen to a `PUSH_ON_BACKGROUND_MESSAGE_PROCESSING_COMPLETE`
    */
   class BackgroundMessageProcessingCompleteReceiver extends BroadcastReceiver {
-    BackgroundMessageProcessingCompleteReceiver(final Context context) {
+    BackgroundMessageProcessingCompleteReceiver(@NonNull final Context context) {
       final IntentFilter filter = new IntentFilter();
       filter.addAction(PUSH_ON_BACKGROUND_MESSAGE_PROCESSING_COMPLETE);
       LocalBroadcastManager.getInstance(context).registerReceiver(this, filter);
@@ -123,6 +118,7 @@ public void onReceive(Context context, Intent intent) {
   void finish() {
     if (asyncProcessingPendingResult != null) {
       asyncProcessingPendingResult.finish();
+      asyncProcessingPendingResult = null;
     }
   }
 }

android/src/main/java/io/ably/flutter/plugin/push/PushBackgroundIsolateRunner.java → android/src/main/java/io/ably/flutter/plugin/push/ManualFlutterApplicationRunner.java

@@ -1,11 +1,10 @@
 package io.ably.flutter.plugin.push;
 
-import static android.content.Context.MODE_PRIVATE;
 import static io.ably.flutter.plugin.generated.PlatformConstants.PlatformMethod.pushOnBackgroundMessage;
 import static io.ably.flutter.plugin.generated.PlatformConstants.PlatformMethod.pushSetOnBackgroundMessage;
 
 import android.content.Context;
-import android.content.SharedPreferences;
+import android.content.Intent;
 import android.util.Log;
 
 import androidx.annotation.NonNull;
@@ -21,20 +20,35 @@
 import io.flutter.plugin.common.MethodChannel;
 import io.flutter.plugin.common.StandardMethodCodec;
 
-public class PushBackgroundIsolateRunner implements MethodChannel.MethodCallHandler {
-  private static final String TAG = PushBackgroundIsolateRunner.class.getName();
-  private static final String SHARED_PREFERENCES_KEY = "io.ably.flutter.plugin.push.PushBackgroundIsolate.SHARED_PREFERENCES_KEY";
-  private static final String BACKGROUND_MESSAGE_HANDLE_KEY = "BACKGROUND_MESSAGE_HANDLE_KEY";
+/**
+ * This class is used when the application was terminated when the push notification is received.
+ * It launches the Flutter application and sends it a RemoteMessage. See [PushMessagingEventHandlers.java]
+ * to see where push notifications being handled whilst the app is in the background or the foreground.
+ * Use this class when no existing Flutter Activity is running.
+ *
+ * This class can be generalized to launch the app manually for any purpose, but currently it is
+ * narrowly scoped for push notifications.
+ */
+public class ManualFlutterApplicationRunner implements MethodChannel.MethodCallHandler {
+  private static final String TAG = ManualFlutterApplicationRunner.class.getName();
   private final FirebaseMessagingReceiver broadcastReceiver;
   private final RemoteMessage remoteMessage;
   private final MethodChannel backgroundMethodChannel;
-
-  @NonNull
   private final FlutterEngine flutterEngine;
 
-  public PushBackgroundIsolateRunner(Context context, FirebaseMessagingReceiver receiver, RemoteMessage message) {
+  /**
+   * Creates a Flutter engine, launches the Flutter application inside that Flutter engine, and
+   * creates a MethodChannel to communicate with the Flutter application.
+   *
+   * @param context
+   * @param receiver The FirebaseMessagingReceiver which received the message
+   * @param intent An intent containing a RemoteMessage passed straight from FirebaseMessagingReceiver
+   */
+  public ManualFlutterApplicationRunner(@NonNull final Context context,
+                                        @NonNull final FirebaseMessagingReceiver receiver,
+                                        @NonNull final Intent intent) {
     this.broadcastReceiver = receiver;
-    this.remoteMessage = message;
+    this.remoteMessage = new RemoteMessage(intent.getExtras());
     flutterEngine = new FlutterEngine(context, null);
     DartExecutor executor = flutterEngine.getDartExecutor();
     backgroundMethodChannel = new MethodChannel(executor.getBinaryMessenger(), "io.ably.flutter.plugin.background", new StandardMethodCodec(new AblyMessageCodec(new CipherParamsStorage())));
@@ -46,18 +60,9 @@ public PushBackgroundIsolateRunner(Context context, FirebaseMessagingReceiver re
     flutterEngine.getBroadcastReceiverControlSurface().attachToBroadcastReceiver(receiver, null);
   }
 
-  /**
-   * This method is called when the main app is running and the user sets the background handler.
-   *
-   * @param backgroundMessageHandlerHandle
-   */
-  public static void setBackgroundMessageHandler(Context context, Long backgroundMessageHandlerHandle) {
-    SharedPreferences preferences = context.getApplicationContext().getSharedPreferences(SHARED_PREFERENCES_KEY, MODE_PRIVATE);
-    preferences.edit().putLong(BACKGROUND_MESSAGE_HANDLE_KEY, backgroundMessageHandlerHandle).apply();
-  }
-
   @Override
-  public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+  public void onMethodCall(@NonNull final MethodCall call,
+                           @NonNull final MethodChannel.Result result) {
     if (call.method.equals(pushSetOnBackgroundMessage)) {
       // This signals that the manually spawned app is ready to receive a message to handle.
       // We ask the user to set the background message handler early on.

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

@@ -5,9 +5,9 @@
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
-import android.os.Bundle;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.localbroadcastmanager.content.LocalBroadcastManager;
 
@@ -16,21 +16,52 @@
 import io.ably.flutter.plugin.generated.PlatformConstants;
 import io.flutter.plugin.common.MethodChannel;
 
+/**
+ * This class is used when the application is in the **foreground** or **background**, but not when
+ * **terminated**. See [PushTerminatedIsolateRunner.java] to see where push notifications being
+ * handled whilst the app is terminated.
+ */
 final public class PushMessagingEventHandlers {
   private static final String TAG = PushMessagingEventHandlers.class.getName();
   public static final String PUSH_ON_MESSAGE_RECEIVED = "io.ably.ably_flutter.PUSH_ON_MESSAGE_RECEIVED";
   public static final String PUSH_ON_BACKGROUND_MESSAGE_RECEIVED = "io.ably.ably_flutter.PUSH_ON_BACKGROUND_MESSAGE_RECEIVED";
   public static final String PUSH_ON_BACKGROUND_MESSAGE_PROCESSING_COMPLETE = "io.ably.ably_flutter.PUSH_ON_BACKGROUND_MESSAGE_COMPLETE";
   static PushMessagingEventHandlers instance;
 
-  public static void instantiate(Context context, MethodChannel methodChannel) {
-    if (instance == null) {
-      instance = new PushMessagingEventHandlers(context, methodChannel);
+  /**
+   * Replaces the existing instance if required. this is because the latest methodChannel is the
+   * most important because it is from the latest plugin registration.
+   * @param context
+   * @param methodChannel
+   */
+  public static void reset(Context context, MethodChannel methodChannel) {
+    if (instance != null) {
+      instance.close(context);
     }
+    instance = new PushMessagingEventHandlers(context, methodChannel);
   }
 
+  private void close(Context context) {
+    this.broadcastReceiver.close(context);
+  }
+
+  private final BroadcastReceiver broadcastReceiver;
   private PushMessagingEventHandlers(Context context, MethodChannel methodChannel) {
-    new BroadcastReceiver(context, methodChannel);
+    this.broadcastReceiver = new BroadcastReceiver(context, methodChannel);
+  }
+
+  // Send message to Dart side app already running
+  public static void sendMessageToFlutterApp(@NonNull final Context context, @NonNull final Intent intent) {
+    final Intent onMessageReceivedIntent = new Intent(PUSH_ON_MESSAGE_RECEIVED);
+    onMessageReceivedIntent.putExtras(intent.getExtras());
+    LocalBroadcastManager.getInstance(context).sendBroadcast(onMessageReceivedIntent);
+  }
+
+  // Flutter is already running, just send a background message to it.
+  public static void sendBackgroundMessageToFlutterApp(Context context, Intent intent) {
+    final Intent onMessageReceivedIntent = new Intent(PUSH_ON_BACKGROUND_MESSAGE_RECEIVED);
+    onMessageReceivedIntent.putExtras(intent.getExtras());
+    LocalBroadcastManager.getInstance(context).sendBroadcast(onMessageReceivedIntent);
   }
 
   private static class BroadcastReceiver extends android.content.BroadcastReceiver {
@@ -48,6 +79,11 @@ private void register(Context context) {
       LocalBroadcastManager.getInstance(context).registerReceiver(this, filter);
     }
 
+    void close(Context context) {
+      LocalBroadcastManager.getInstance(context).unregisterReceiver(this);
+      this.methodChannel = null;
+    }
+
     @Override
     public void onReceive(Context context, Intent intent) {
       String action = intent.getAction();

lib/src/platform/src/platform.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:ably_flutter/src/platform/src/background_android_isolate_platform.dart';
 import 'package:flutter/services.dart';
 
 import '../../error/error.dart';
@@ -28,6 +29,7 @@ class Platform {
     if (_initializer == null) {
       AblyMethodCallHandler(methodChannel);
       _initializer = methodChannel.invokeMethod(PlatformMethod.registerAbly);
+      BackgroundIsolateAndroidPlatform();
     }
     return _initializer;
   }