Cannot cast double values as String to textview

Question

I got a null pointer exeption error on Attempt to invoke virtual method void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference.

public class MainActivity {
    TextView servingqueue;
}

This is onCreate

    DatabaseReference mRootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference mServingQueue = mRootRef.child("ServingQueue");

servingqueue = (TextView) findViewById(R.id.queueServing);

mServingQueue.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Double number = dataSnapshot.getValue(Double.class);
        servingqueue.setText(String.valueOf(number));
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }

The error appeared right on

servingqueue.setText(String.valueOf(number));

It just does not want to pass the value from Firebase to my textview. I get force close from my app upon loading the activity.

Answer 1

First Cast Double to double(primitive) then Cast it to String

Double number = dataSnapshot.getValue(Double.class);
 double d=number.doubleValue();
        servingqueue.setText(String.valueOf(d));