JakeWharton

/* Base fragment to ensure the parent activity implements a contract interface. */
public abstract class ContractFragment<T> extends Fragment {
    private T mContract;

    @Override
    public void onAttach(Activity activity) {
        try {
            mContract = (T)activity;
        } catch (ClassCastException e) {
            throw new IllegalStateException(activity.getClass().getSimpleName()