Question

I am trying to implement a ListView with test values. It should display 2 strings per list element. But i get a NullPointerException.

I have a ListActivity, calling an Adapter. If I comment the last line of this activity, I don’t have any error so I guess that my adaptator has something wrong. But I have searched solutions on the Web, and unfortunatelly, I cannot solve my problem due to a very low Java (and OOP) skill. Can you please tell me where I mad a mistake ?

public class ListActivity extends Activity {

//private final String TAG = ListActivity.class.getSimpleName();
private ListView listMessView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_list);

    List<Message> listMessages = new ArrayList<Message>();
    listMessages.add(new Message("London", "aze"));
    listMessages.add(new Message("Rome", "azeeaze"));
    listMessages.add(new Message("Paris", "qsdqsdqsd"));

    listMessView =  (ListView) findViewById(R.id.message_list);
    listMessView.setAdapter(new ListAdaptater(this, R.layout.list_row, listMessages));
    }
}


public class ListAdaptater extends ArrayAdapter<Message>{

  private int resource;
  private LayoutInflater inflater;
  private Context context;

  public ListAdaptater ( Context ctx, int resourceId, List<Message> objects) {

        super( ctx, resourceId, objects );
        resource = resourceId;
        inflater = LayoutInflater.from( context );
        context=ctx;
  }

  @Override
  public View getView ( int position, View convertView, ViewGroup parent ) {

        convertView = ( RelativeLayout ) inflater.inflate( resource, null );

        Message message = (Message) getItem( position );

        TextView txtName = (TextView) convertView.findViewById(R.id.user_name);
        txtName.setText(message.getUserName());

        TextView txtMsg = (TextView) convertView.findViewById(R.id.message);
        txtMsg.setText(message.getMessage());

        return convertView;
  }
  }

Answer 1

The field context is used before it’s initialized. Try using this:

  public ListAdaptater ( Context ctx, int resourceId, List<Message> objects) {

        super( ctx, resourceId, objects );
        resource = resourceId;
        inflater = LayoutInflater.from( ctx );
        context=ctx;
  }