Android-如何从其他类动态添加ListView项

Question

I am developing simple text messaging app using FCM (latest GCM), where I have an activity called ChatActivity that shows list of messages using ListView.

However, when any new message arrives it will be handled by FirebaseMessagingService class...

public class MyFcmListenerService extends FirebaseMessagingService {

    @override
    public void onMessageReceived(RemoteMessage remoteMessage) {

        String from = remoteMessage.getFrom();
        Map<String, String> data = remoteMessage.getData();
        String body = rawData.get("body");

        Log.i("From",from);
        Log.i("Message",body);

    }
}

This class prints message in console successfully whenever any new message arrives.

My question is, when I get a new message from FCM in onMessageReceived() class, how can I add that String message to the ListView in ChatActivity ?

And, after adding item to the ListView, how can I call .notifyDataSetChanged() on ListView Adaptor ?

Answer 1

There are many ways you can pass data to an Activity and by extension a ListView upon receiving a message. One simple way is to set up a BroadcastReceiver in your Activity and then when you receive your FCM message you can use LocalBroadcastManager to send a broadcast indicating that your activity should update the ListView's adapter. See LocalBroadcastManager for more.

@McAwesomville suggests using Firebase Realtime Database , is also an option, you can see it in use for a simple chat app in the Firebase Android Codelab .

Answer 2

I am using FirebaseUI in my app and it works very well. You can read more about it here.