android - onAttach(Activity) deprecated: where I can check if the activity implements callback interface

Question

Before API 23 I used Fragment's onAttach methods to get my listener instance, then the reference is cleaned inside onDetach. ex:

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    mListener = null;
    try {
        mListener = (SellFragmentListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement SellFragmentListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

Is it safe to do the same check inside onAttach(Context context) or is there a better way to get the holder activity instance?

Answer 1

Check the source code:

/**
 * Called when a fragment is first attached to its context.
 * {@link #onCreate(Bundle)} will be called after this.
 */
public void onAttach(Context context) {
    mCalled = true;
    final Activity hostActivity = mHost == null ? null : mHost.getActivity();
    if (hostActivity != null) {
        mCalled = false;
        onAttach(hostActivity);
    }
}

/**
 * @deprecated Use {@link #onAttach(Context)} instead.
 */
@Deprecated
public void onAttach(Activity activity) {
    mCalled = true;
}

So the onAttach(Activity activity) is called by the onAttach(Context context) if there is a host activity. You can use the onAttach(Activity activity) safely.