添加Firebase子级后，在Android中获得通知

Question

I am trying to get an android notification when a Fire base Database child has been added to the database using listeners, but unable to get the notification. I have coded this little test app which doesn't show an notification when the app is run, or even on background. Can someone please look into this, and help me out, I am still a beginner, a little help would be wonderful!

package com.fayaz.firebasenotify;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import android.app.NotificationManager;
import android.support.v4.app.NotificationCompat;
import android.view.View;


public class MainActivity extends AppCompatActivity {

private FirebaseDatabase myFirebaseRef = FirebaseDatabase.getInstance();
private DatabaseReference myRef =  myFirebaseRef.getReference();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

}

NotificationCompat.Builder builder = new NotificationCompat.Builder(this);

public void sendNotification(View view) {
    ValueEventListener valueEventListener = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            builder.setSmallIcon(R.mipmap.ic_launcher);
            builder.setContentTitle("Firebase Push Notification");
            builder.setContentText("Hello this is a test Firebase notification, a new database child has been added");
            NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            notificationManager.notify(1, builder.build());
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.i("FirebaseError", databaseError.getMessage());
        }

    };
    myRef.addValueEventListener(valueEventListener);
}
}

Answer 1

You should use ChildEventListener,

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mRootRef = FirebaseDatabase.getInstance().getReference();
    builder = new NotificationCompat.Builder(this);
    mRootRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            builder.setSmallIcon(R.mipmap.ic_launcher);
            builder.setContentTitle("Firebase Push Notification");
            builder.setContentText("Hello this is a test Firebase notification, a new database child has been added");
            NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            notificationManager.notify(1, builder.build());
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

Make sure you can read the data from the database (check security rules).