[firebase_messaging] Updated Getting Started

packages/firebase_messaging/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.0.17
+
+* Update README to work with background notification for Android
+
 ## 6.0.16
 
 * Fix push notifications clearing after app launch on iOS.

packages/firebase_messaging/README.md

@@ -73,34 +73,55 @@ By default background messaging is not enabled. To handle messages in the backgr
 
    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>/`.
+1. Add an `FirebaseCloudMessagingPluginRegistrant.kt` class to your app in the same directory as your `MainActivity.kt`. This is typically found in `<app-name>/android/app/src/main/kotlin/<app-organization-path>/`.
+
+  ```kt
+    import io.flutter.plugin.common.PluginRegistry
+    import io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin
+
+
+    object FirebaseCloudMessagingPluginRegistrant {
+        fun registerWith(registry: PluginRegistry) {
+            if (alreadyRegisteredWith(registry)) {
+                return
+            }
+            FirebaseMessagingPlugin.registerWith(registry.registrarFor("io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin"))
+        }
+
+        private fun alreadyRegisteredWith(registry: PluginRegistry): Boolean {
+            val key = FirebaseCloudMessagingPluginRegistrant::class.java.canonicalName
+            if (registry.hasPlugin(key)) {
+                return true
+            }
+            registry.registrarFor(key)
+            return false
+        }
+    }
+  ```
+1. Add an `Application.kt` class to your app in the same directory as your `MainActivity.kt`. This is typically found in `<app-name>/android/app/src/main/kotlin/<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);
-     }
-   }
-   ```
+  ```kt
+    import io.flutter.app.FlutterApplication
+    import io.flutter.plugin.common.PluginRegistry
+    import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback
+    import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService
+
+
+    class Application : FlutterApplication(), PluginRegistrantCallback {
+        override fun onCreate() {
+            super.onCreate()
+            FlutterFirebaseMessagingService.setPluginRegistrant(this)
+        }
+
+        override fun registerWith(registry: PluginRegistry) {
+            FirebaseCloudMessagingPluginRegistrant.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`.
+1. In `Application.kt` and `FirebaseCloudMessagingPluginRegistrant.kt`, 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
+   ```kt
    package com.domain.myapplication;
    ```
 
@@ -129,7 +150,7 @@ By default background messaging is not enabled. To handle messages in the backgr
    ```
 
    Note: the protocol of `data` and `notification` are in line with the
-   fields defined by a [RemoteMessage](https://firebase.google.com/docs/reference/android/com/google/firebase/messaging/RemoteMessage). 
+   fields defined by a [RemoteMessage](https://firebase.google.com/docs/reference/android/com/google/firebase/messaging/RemoteMessage). You may also need to force stop or uninstall & reinstall the app to make the background notifications work.
 
 1. Set `onBackgroundMessage` handler when calling `configure`