Utility method for getting the appropriate parent of a Fragment for a given callback interface.

FragmentUtils.java

import android.support.v4.app.Fragment;

public class FragmentUtils {

  /**
   * @param fragment
   *            The Fragment whose parent is to be found
   * @param parentClass
   *            The interface that the parent should implement
   * @return The parent of fragment that implements parentClass,
   *         null, if no such parent can be found
   */
  @Nullable
  public static <T> T getParent(@NonNull Fragment fragment, @NonNull Class<T> parentClass) {
    Fragment parentFragment = fragment.getParentFragment();
    if (parentClass.isInstance(parentFragment)) {
      //Checked by runtime methods
      //noinspection unchecked
      return (T) parentFragment;
    } else if (parentClass.isInstance(fragment.getActivity())) {
      //Checked by runtime methods
      //noinspection unchecked
      return (T) fragment.getActivity();
    }
    return null;
  }
}

LICENSE

Copyright 2015 Joshua Brown

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Maybe change to while to check if grandparent of parent fragment implements callback?

Could you give this gist an explicit license? Maybe Apache 2.0?

Nice utillity! Btw, you don't need to explicitly check if the parentFragment and activity are null. Class#isInstance(...) returns false if the argument is null.

When is the best place to call this on a a fragment recreate (e.g. on a rotation)? Obviously if you know you are child of an activity you can use the onAttach() lifecycle call back.