When an app is in background, onMessageReceived method is not firing

问题

Actually i need to show badge in app icon but i don't know how to get badge and why onMessageReceived not call when app is in background or app is not running.

public class Custom_FirebaseMessagingService extends FirebaseMessagingService          {
            private static final String TAG = "FirebaseMsgService";
            String activityName;

            @Override
            public void onMessageReceived(RemoteMessage remoteMessage) {

                if (remoteMessage == null)
                    return;
                if (remoteMessage.getNotification() != null) {
                    Log.i(TAG, "Notification Body: " + remoteMessage.getNotification().getBody());
                }
                // Check if message contains a data payload.
                if (remoteMessage.getData().size() > 0) {
                    Log.i(TAG, "Data Payload: " + remoteMessage.getData().toString());
                    try{
                        //boolean from_bg = Boolean.parseBoolean(remoteMessage.getData().get("from_bg").toString());
                        Map<String, String> data = remoteMessage.getData();
                        boolean show_fg =  Boolean.parseBoolean(data.get("show_fg"));
                        ..... 

回答1:

There are two types of FCM

notification Messages: Sending a payload with this message type triggers onMessageReceived() only when your app is in foreground.

data Messages: Sending a payload with only this specific message type triggers onMessageReceived() regardless if your app is in foreground/background.

Reference: https://firebase.google.com/docs/cloud-messaging/android/receive#handling_messages

回答2:

Add service to AndroidManifest.xml. Also make sure token is not expired.

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

Refresh Token if it is expired.

@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);
}

来源：https://stackoverflow.com/questions/44152037/when-an-app-is-in-background-onmessagereceived-method-is-not-firing