Firebase “Failed to convert a value of type java.util.HashMap to int”

Question

At this line of my code in my OnDataChange() method in the ValueEvenListener:

int latest = dataSnapshot.getValue(Integer.class);


        

Answer 1

This should work if we assume that the dataSnapshot is right.

final DatabaseReference database = FirebaseDatabase.getInstance().getReference();
database = database.child("Campaigns").child(key).child("count"); // replaced

        database.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                int latest = Integer.valueOf(dataSnapshot.getValue().toString()); // replaced
                button.setText(latest + "");
            }

            @Override
        public void onCancelled(DatabaseError databaseError) {
            Toast.makeText(context, context.getString(R.string.error) + ": " + databaseError.getMessage(), Toast.LENGTH_SHORT).show();
        }
    });

Reminder : addValueEventListener will run everytime there is a change in the dataSnapshot. If you want to run it just once use addListenerForSingleValueEvent instead.

Answer 2

Your ValueEventListener is attached to the whole database.

// This line gets a reference to the whole database
final DatabaseReference database =  FirebaseDatabase.getInstance().getReference();

// This line creates a child DatabaseReference, but you don't assign
// the child to a variable
database.child("Campaigns").child(key).child("count");

// This line adds a ValueEventListener to the whole database
database.addValueEventListener(new ValueEventListener() {

What you want instead is this:

final DatabaseReference database = FirebaseDatabase.getInstance().getReference()
final DatabaseReference countRef = database.child("Campaigns").child(key).child("count")
countRef.addValueEventListener(new ValueEventListener() {
    // ...
});

You can see that in the latter example the ValueEventListener is attached to the child reference, not to the root.

Answer 3

It turns out I had to child dataSnapshot to my destination again. E.g:

int latest = dataSnapshot.child("Campaigns").child(key).child("count").getValue(Integer.class);

By default dataSnapshot is actually my whole database.