In the onCreate() method, add the line of code that requests the progress indicator window feature. Here's some helpful

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import com.parse.ParseUser;
import com.parse.ParseException;
import com.parse.SignUpCallback;

public class SignUpActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // rest of code omitted
    }

    protected void signUp(String username, String password) {
        ParseUser newUser = new ParseUser();
        newUser.setUsername(username);
        newUser.setPassword(password);
        newUser.signUpInBackground(new SignUpCallback() {
            @Override
            public void done(ParseException e) {
                // some code omitted
            }
        });
    }
}