Unable to connect to firebase DB from my android app

问题

I am unable to connect to my firebase DB.

My code:

DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference("error");
mDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                try {
                    //getting value as dataSnapshot;
                } catch (Exception ignored) { }
            }

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

OnDataChange() and onCancelled() are not getting triggered and "error" is my collection name in firebase DB console.

My firebase dependencies in app build file:

implementation "com.google.firebase:firebase-database:16.0.5"
implementation 'com.google.firebase:firebase-auth:16.0.5'
implementation "com.google.firebase:firebase-core:16.0.1"

来源：https://stackoverflow.com/questions/53396190/unable-to-connect-to-firebase-db-from-my-android-app