Set Up a Firebase Cloud Messaging Client App on Android

To write your Firebase Cloud Messaging Android client app, use the FirebaseMessaging API and Android Studio 1.4 or higher with Gradle. The instructions in this page assume that you have completed the steps for adding Firebase to your Android project.

FCM clients require devices running Android 4.0 or higher that also have the Google Play Store app installed, or an emulator running Android 4.0 with Google APIs. Note that you are not limited to deploying your Android apps through Google Play Store.

Set up Firebase and the FCM SDK

1. If you haven't already, add Firebase to your Android project.

2. In Android Studio, add the FCM dependency to your app-level build.gradle file:

   dependencies {
        compile 'com.google.firebase:firebase-messaging:11.2.0'
   }

Edit your app manifest

Add the following to your app's manifest:

• A service that extends FirebaseMessagingService. This is required if you want to do any message handling beyond receiving notifications on apps in the background. To receive notifications in foregrounded apps, to receive data payload, to send upstream messages, and so on, you must extend this service.

<service
    android:name=".MyFirebaseMessagingService">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT"/>
    </intent-filter>
</service>
AndroidManifest.xml

• A service that extends FirebaseInstanceIdService to handle the creation, rotation, and updating of registration tokens. This is required for sending to specific devices or for creating device groups.

<service
    android:name=".MyFirebaseInstanceIDService">
    <intent-filter>
        <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
    </intent-filter>
</service>
AndroidManifest.xml

• (Optional) Within the application component, metadata elements to set a default icon, color and notification channel (new in Android O) for notifications. Android uses these values whenever incoming messages do not explicitly set icon, color or notification_channel.

<!-- Set custom default icon. This is used when no icon is set for incoming notification messages.
     See README(https://goo.gl/l4GJaQ) for more. -->
<meta-data
    android:name="com.google.firebase.messaging.default_notification_icon"
    android:resource="@drawable/ic_stat_ic_notification" />
<!-- Set color used with incoming notification messages. This is used when no color is set for the incoming
     notification message. See README(https://goo.gl/6BKBk7) for more. -->
<meta-data
    android:name="com.google.firebase.messaging.default_notification_color"
    android:resource="@color/colorAccent" />
AndroidManifest.xml

• If FCM is critical to the Android app's function, be sure to set minSdkVersion 8 or higher in the app's build.gradle. This ensures that the Android app cannot be installed in an environment in which it could not run properly.

Access the device registration token

On initial startup of your app, the FCM SDK generates a registration token for the client app instance. If you want to target single devices or create device groups, you'll need to access this token by extending FirebaseInstanceIdService.

This section describes how to retrieve the token and how to monitor changes to the token. Because the token could be rotated after initial startup, you are strongly recommended to retrieve the latest updated registration token.

The registration token may change when:

• The app deletes Instance ID
• The app is restored on a new device
• The user uninstalls/reinstall the app
• The user clears app data.

Retrieve the current registration token

When you need to retrieve the current token, call FirebaseInstanceId.getInstance().getToken(). This method returns null if the token has not yet been generated.

Monitor token generation

The onTokenRefreshcallback fires whenever a new token is generated, so calling getToken in its context ensures that you are accessing a current, available registration token. Make sure you have added the service to your manifest, then call getToken in the context of onTokenRefresh, and log the value as shown:

@Override
public void onTokenRefresh() {
    // Get updated InstanceID token.
    String refreshedToken = FirebaseInstanceId.getInstance().getToken();
    Log.d(TAG, "Refreshed token: " + refreshedToken);

    // If you want to send messages to this application instance or
    // manage this apps subscriptions on the server side, send the
    // Instance ID token to your app server.
    sendRegistrationToServer(refreshedToken);
}
MyFirebaseInstanceIDService.java

After you've obtained the token, you can send it to your app server and store it using your preferred method. See the Instance ID API reference for full detail on the API.

Check for Google Play services

Apps that rely on the Play Services SDK should always check the device for a compatible Google Play services APK before accessing Google Play services features. It is recommended to do this in two places: in the main activity's onCreate() method, and in its onResume() method. The check in onCreate() ensures that the app can't be used without a successful check. The check in onResume() ensures that if the user returns to the running app through some other means, such as through the back button, the check is still performed.

If the device doesn't have a compatible version of Google Play services, your app can call GoogleApiAvailability.makeGooglePlayServicesAvailable() to allow users to download Google Play services from the Play Store.

Next steps

After the client app is set up, you are ready to start sending downstream messages with the Notifications composer. This functionality is demonstrated in the quickstart sample, which you can download, run, and review.

To add other, more advanced behavior to your app, you can declare an intent filter and implement an activity to respond to incoming messages. For details, see the guides for sending messages from an app server:

• Send topic messages
• Send to device groups
• Send upstream messages

Keep in mind that, to take advantage of these features, you'll need a server implementation and the server procotols (HTTP or XMPP), or an implementation of the Admin SDK.