flat

adapter.java

/* within adapter class */

private static class ItemDeletate<T> {

  private final T item;
  private boolean isViewed;

  public ItemDelegate(T item) {
    this.item = item;
  }
  
}

callback.java

public class MyFragment extends Fragment {
  
  private MyInterface myInterface = null;
  
  public interface MyInterface {
    void function1();
  }
  
  @Override
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    
    try {
      myInterface = (MyInterface) activity;
    } catch (ClassCastException e) {
      throw new ClassCastException(activity.toString()
        + " must implement MyFragment.MyInterface");
    }
  }
  
  @Override
  public void onActivityCreated(/* ... */) {
    myInterface.function1();
  }
}

/* ... */

public class MyActivity extends Activity implements MyFragment.MyInterface {
  
  @Override
  public void function1() {
    /* ... */
  }
  
}