Using getIdentifier() to Find ID of Image

Issue

I am trying to get id of an image by using following code.

 public class MovieActivity extends ActionBarActivity {
        private Context con;
        String name = "test";
        protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                con = MovieActivity.this;
                setContentView(R.layout.activity_movie);
            }

    public void updateScreen(){

            int imageResource = con.getResources().getIdentifier("drawable/" + name , null, con.getPackageName());

        }

    }

When I run it, I get exception:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference

I thought the problem was Context so I added con variable which gets context when code runs. I made some researches and tried another methods but I got same exception every time. Can anyone help me?

EDIT: When I use the same code line in MainActivity, it works perfectly. But in another class, it fails.

public class SomeMovie extends MovieActivity {  }

public class MainActivity extends ActionBarActivity {

     protected void onCreate(Bundle savedInstanceState) {
          SomeMovie movie = new SomeMovie();
          movie.updateScreen();

      }
 }

SomeMovie class is child of MovieActivity class. I call the method on that. I debugged the code and noticed that Context is null when code gets into updateScreen() method. Is it wrong to use inheritance on activity classes?

Solution

Change

int imageResource = con.getResources().getIdentifier("drawable/" + name , null, con.getPackageName());

to

int imageResource = getResources().getIdentifier("drawable/" + name , null, con.getPackageName());

You are already in an Activity's context, so use it. (No need to use the this keyword to refer to it)

EDIT:

You are not defining a layout for the SomeMovie Activity, so its context is always null. You have to define the activity's layout in its onCreate method :

public class SomeMovie extends MovieActivity {

     protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.somemoviexml);
          ...

      }
 }

Answered By - Mohammed Aouf Zouag