title: Fragment Error : incompatible types,required android.app.fragment but found activity.messagefragment
body: <pre><code> @Override
  public void onDrawerItemSelected(View view, int position) {
      displayView(position);
  }
  
  private void displayView(int position) {
      Fragment fragment = null;
      String title = getString(R.string.app_name);
      switch (position) {
          case 0:
              fragment = new HomeFragment();
              title = getString(R.string.title_home);
              break;
          case 1:
              fragment = new FriendsFragment();
              title = getString(R.string.title_friends);
              break;
          case 2:
              fragment = new MessageFragment();
              title = getString(R.string.title_messages);
              break;
          default:
              break;
      }
  </code></pre>
  
  <p>the error printed is:</p>
  
  <pre><code>incompatible types,required android.app.fragment but found activity.messagefragment
  </code></pre>