[firebase_messaging] Android: background service refactoring

packages/firebase_messaging/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 8.0.0
+
+* Refactors the Android portion for background messages. It is now using a
+  `FlutterEngine` internally, which does removes the requirement to manually
+  register a plugin registrant or include FCM dependencies in the host App.
+
 ## 7.0.0
 
 * Depend on `firebase_core` and migrate plugin to use `firebase_core` native SDK versioning features;

packages/firebase_messaging/README.md

@@ -61,55 +61,6 @@ for more.
 
 By default background messaging is not enabled. To handle messages in the background:
 
-1. Add the `com.google.firebase:firebase-messaging` dependency in your app-level `build.gradle` file that is typically located at `<app-name>/android/app/build.gradle`.
-
-   ```gradle
-   dependencies {
-     // ...
-
-     implementation 'com.google.firebase:firebase-messaging:<latest_version>'
-   }
-   ```
-
-   Note: you can find out what the latest version of the plugin is [here ("Cloud Messaging")](https://firebase.google.com/support/release-notes/android#latest_sdk_versions).
-
-1. Add an `Application.java` class to your app in the same directory as your `MainActivity.java`. This is typically found in `<app-name>/android/app/src/main/java/<app-organization-path>/`.
-
-   ```java
-   package io.flutter.plugins.firebasemessagingexample;
-
-   import io.flutter.app.FlutterApplication;
-   import io.flutter.plugin.common.PluginRegistry;
-   import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback;
-   import io.flutter.plugins.GeneratedPluginRegistrant;
-   import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService;
-
-   public class Application extends FlutterApplication implements PluginRegistrantCallback {
-     @Override
-     public void onCreate() {
-       super.onCreate();
-       FlutterFirebaseMessagingService.setPluginRegistrant(this);
-     }
-
-     @Override
-     public void registerWith(PluginRegistry registry) {
-       GeneratedPluginRegistrant.registerWith(registry);
-     }
-   }
-   ```
-
-1. In `Application.java`, make sure to change `package io.flutter.plugins.firebasemessagingexample;` to your package's identifier. Your package's identifier should be something like `com.domain.myapplication`.
-
-   ```java
-   package com.domain.myapplication;
-   ```
-
-1. Set name property of application in `AndroidManifest.xml`. This is typically found in `<app-name>/android/app/src/main/`.
-
-   ```xml
-   <application android:name=".Application" ...>
-   ```
-
 1. Define a **TOP-LEVEL** or **STATIC** function to handle background messages
 
    ```dart

packages/firebase_messaging/android/src/main/java/io/flutter/plugins/firebasemessaging/FirebaseMessagingPlugin.java

@@ -29,6 +29,8 @@
 import io.flutter.plugin.common.MethodChannel.Result;
 import io.flutter.plugin.common.PluginRegistry.NewIntentListener;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
+import io.flutter.plugin.common.PluginRegistry.ViewDestroyListener;
+import io.flutter.view.FlutterNativeView;
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
@@ -41,31 +43,33 @@ public class FirebaseMessagingPlugin extends BroadcastReceiver
   private static final String TAG = "FirebaseMessagingPlugin";
 
   private MethodChannel channel;
-  private Context applicationContext;
   private Activity mainActivity;
 
-  public static void registerWith(Registrar registrar) {
-    FirebaseMessagingPlugin instance = new FirebaseMessagingPlugin();
+  public static void registerWith(final Registrar registrar) {
+    final FirebaseMessagingPlugin instance = new FirebaseMessagingPlugin();
     instance.setActivity(registrar.activity());
     registrar.addNewIntentListener(instance);
     instance.onAttachedToEngine(registrar.context(), registrar.messenger());
+    registrar.addViewDestroyListener(
+        new ViewDestroyListener() {
+          @Override
+          public boolean onViewDestroy(FlutterNativeView view) {
+            instance.onDetachedFromEngine(registrar.context());
+            return false;
+          }
+        });
   }
 
   private void onAttachedToEngine(Context context, BinaryMessenger binaryMessenger) {
-    this.applicationContext = context;
     channel = new MethodChannel(binaryMessenger, "plugins.flutter.io/firebase_messaging");
-    final MethodChannel backgroundCallbackChannel =
-        new MethodChannel(binaryMessenger, "plugins.flutter.io/firebase_messaging_background");
 
     channel.setMethodCallHandler(this);
-    backgroundCallbackChannel.setMethodCallHandler(this);
-    FlutterFirebaseMessagingService.setBackgroundChannel(backgroundCallbackChannel);
 
     // Register broadcast receiver
     IntentFilter intentFilter = new IntentFilter();
     intentFilter.addAction(FlutterFirebaseMessagingService.ACTION_TOKEN);
     intentFilter.addAction(FlutterFirebaseMessagingService.ACTION_REMOTE_MESSAGE);
-    LocalBroadcastManager manager = LocalBroadcastManager.getInstance(applicationContext);
+    LocalBroadcastManager manager = LocalBroadcastManager.getInstance(context);
     manager.registerReceiver(this, intentFilter);
   }
 
@@ -80,7 +84,11 @@ public void onAttachedToEngine(FlutterPluginBinding binding) {
 
   @Override
   public void onDetachedFromEngine(FlutterPluginBinding binding) {
-    LocalBroadcastManager.getInstance(binding.getApplicationContext()).unregisterReceiver(this);
+    onDetachedFromEngine(binding.getApplicationContext());
+  }
+
+  private void onDetachedFromEngine(Context applicationContext) {
+    LocalBroadcastManager.getInstance(applicationContext).unregisterReceiver(this);
   }
 
   @Override
@@ -149,14 +157,10 @@ public void onMethodCall(final MethodCall call, final Result result) {
     /*  Even when the app is not active the `FirebaseMessagingService` extended by
      *  `FlutterFirebaseMessagingService` allows incoming FCM messages to be handled.
      *
-     *  `FcmDartService#start` and `FcmDartService#initialized` are the two methods used
-     *  to optionally setup handling messages received while the app is not active.
+     *  `FcmDartService#start` is setup to handle messages received while the app is not active.
      *
      *  `FcmDartService#start` sets up the plumbing that allows messages received while
      *  the app is not active to be handled by a background isolate.
-     *
-     *  `FcmDartService#initialized` is called by the Dart side when the plumbing for
-     *  background message handling is complete.
      */
     if ("FcmDartService#start".equals(call.method)) {
       long setupCallbackHandle = 0;
@@ -171,12 +175,10 @@ public void onMethodCall(final MethodCall call, final Result result) {
         e.printStackTrace();
       }
       FlutterFirebaseMessagingService.setBackgroundSetupHandle(mainActivity, setupCallbackHandle);
-      FlutterFirebaseMessagingService.startBackgroundIsolate(mainActivity, setupCallbackHandle);
       FlutterFirebaseMessagingService.setBackgroundMessageHandle(
           mainActivity, backgroundMessageHandle);
-      result.success(true);
-    } else if ("FcmDartService#initialized".equals(call.method)) {
-      FlutterFirebaseMessagingService.onInitialized();
+      mainActivity.startService(new Intent(mainActivity, FlutterFirebaseMessagingService.class));
+
       result.success(true);
     } else if ("configure".equals(call.method)) {
       FirebaseInstanceId.getInstance()