findViewById() not working in a not MainActivity class

Question

I have a text view in my Lyout and I would like to set some text to this textview. This should be made in a class which is not a MainActivity class.

The problem is that I got a null pointer exception.

Here is my code:

public class UserInformations extends Activity{  TextView emailTextView; LocalDatabase localdatabase= new LocalDatabase(this);       public void getUserInformation()     {     emailTextView = (TextView) findViewById(R.id.EmailTextView);     String email = localdatabase.getUserEmail();     emailTextView.setText(email);     } } 

When I am doing this in the Main Activity class, it works, but it doesn't work not in another class.

Answer 1

Calling findViewById() on the Activity object will only work if the current Activity layout is set by setContentView. If you add a layout through some other means, then you need the View object of the layout and call findViewById() on it.

View v = inflater.inflate(id_number_of_layout); # such as R.layout.activity_main View innerView = v.findViewById(id_number_of_view_inside_v); 

If the layout is supposed to be the main layout of the activity, then do this:

public class MyActivity extends Activity{   TextView emailTextView;     @Override   public void onCreate(Bundle savedInstanceState){      super.onCreate(savedInstanceState);      setContentView(id_number_of_layout);      emailTextView = (TextView) findViewById(R.id.EmailTextView);      // ... whatever other set up you need to do ...   }    public void getUserInformation() {      // .... regular code ...    } }