How to retrieve values from current signed in User Firebase,Android

Question

I'm not able to retrieve any of the values from my datasnapshot. I've tried several methods and techniques, but it's given a null value.

The image of my database is above. Please see my code below,trying to log a value, everything seems right but not working.

email = view.findViewById(R.id.email);
editTextfragmentF = view.findViewById(R.id.editText_firstname);
editTextfragmentL = view.findViewById(R.id.editText_lastname);

    FirebaseAuth mAuth = FirebaseAuth.getInstance();
    String UserID = mAuth.getCurrentUser().getUid();

    FirebaseDatabase database = FirebaseDatabase.getInstance();
    database.getReference().child("Users").child(UserID).addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
            if (mAuth.getCurrentUser() != null) {
                email.setText(mAuth.getCurrentUser().getEmail());

                //Gets current users first name
                String FN = String.valueOf(dataSnapshot.child("firstName").getValue());
                Log.i("First Name", FN);

                /*String LN = dataSnapshot.child("lastName").getValue().toString();
                Log.i("Last Name", LN);*/
                /*editTextfragmentF.setText(FN);
                editTextfragmentF.requestFocus();*/

                /*editTextfragmentL.setText(LN);
                editTextfragmentL.requestFocus();*/
            }
        }

The Result:

Answer 1

you need to change

database.getReference().child("Users").child(UserID).addChildEventListener

with

    database.getReference().child("Users").child(UserID).addValueEventListener(new ValueEventListener() {
      @Override
      public void onDataChange(DataSnapshot dataSnapshot) {
        email.setText(dataSnapshot.child("email").getValue(String.class));
        String FN = dataSnapshot.child("firstName").getValue(String.class);
        Log.i("First Name", FN);
      }

      @Override
      public void onCancelled(DatabaseError databaseError) {
        System.out.println("The read failed: " + databaseError.getCode());
      }
    });

Make sure you have granted internet access in your AndroidManifest.xml

<manifest xlmns:android...>
 ...
 <uses-permission android:name="android.permission.INTERNET" />
 <application ...
</manifest>

Answer 2

getValue() takes in type of object to be returned. In your case your are getting a string value so just pass String.class into the method then save it into a String variable.

String firstname=dataSnapshot.getValue(String.class);
Log.i("First Name", firstname);