android - Cannot get the value out of firebase with .getValue()

Question

I am new to Java, Android, and Firebase. What I am trying to do here is read what's already uploaded to firebase, but the code doesn't work. I put a breakpoint and found that it doesn't even run the listener. What is the problem here? Any help is much appreciated.

Here is my database on Firebase:

This is the code I used to retrieve the information from the database.

//in Main Activity
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference(); 

//Rest of the code is within onCreate()
mDatabase.child("9099").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                 String number = dataSnapshot.child("Number").getValue().toString();
                 String time = dataSnapshot.child("Time").getValue().toString();
                 String chan1 = dataSnapshot.child("Channel1").getValue().toString();
                 String chan2 = dataSnapshot.child("Channel2").getValue().toString();
                 testing.setText(String.format(time));
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });

Answer 1

等待大神答复