两个类，让你再也不用实现onActivityResult()

当我们知道fragment仅仅可以收到自己请求的回调后，我们就可以用它来解耦activity中onActivityResult的逻辑了。一般情况下，如果一个activity中多个回调结果的话，onActivityResult()中会有各种case判断，并且这种设计也打断了流式写法。那么我们索性建立一个无UI的fragment做精准的接收器，这样就可以再也不写onActivityResult()了。

Fragment：

/**
 * @author Kale
 * @date 2018/4/13
 */
public class OnActResultEventDispatcherFragment extends Fragment {

    public static final String TAG = "on_act_result_event_dispatcher";

    private SparseArray<ActResultRequest.Callback> mCallbacks = new SparseArray<>();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    public void startForResult(Intent intent, ActResultRequest.Callback callback) {
        mCallbacks.put(callback.hashCode(), callback);
        startActivityForResult(intent, callback.hashCode());
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        ActResultRequest.Callback callback = mCallbacks.get(requestCode);
        mCallbacks.remove(requestCode);

        if (callback != null) {
            callback.onActivityResult(resultCode, data);
        }
    }

}

请求封装类：

public class ActResultRequest {

    private OnActResultEventDispatcherFragment fragment;

    public ActResultRequest(Activity activity) {
        fragment = getEventDispatchFragment(activity);
    }

    private OnActResultEventDispatcherFragment getEventDispatchFragment(Activity activity) {
        final FragmentManager fragmentManager = activity.getFragmentManager();

        OnActResultEventDispatcherFragment fragment = findEventDispatchFragment(fragmentManager);
        if (fragment == null) {
            fragment = new OnActResultEventDispatcherFragment();
            fragmentManager
                    .beginTransaction()
                    .add(fragment, OnActResultEventDispatcherFragment.TAG)
                    .commitAllowingStateLoss();
            fragmentManager.executePendingTransactions();
        }
        return fragment;
    }

    private OnActResultEventDispatcherFragment findEventDispatchFragment(FragmentManager manager) {
        return (OnActResultEventDispatcherFragment) manager.findFragmentByTag(OnActResultEventDispatcherFragment.TAG);
    }

    public void startForResult(Intent intent, Callback callback) {
        fragment.startForResult(intent, callback);
    }

    public interface Callback {

        void onActivityResult(int resultCode, Intent data);
    }
}

发送请求和监听请求的代码：

Intent intent = new Intent(this, SecondActivity.class);

request.startForResult(intent, new ActResultRequest.Callback() {
    @Override
    public void onActivityResult(int resultCode, Intent data) {
        Toast.makeText(MainActivity.this, "" + resultCode, Toast.LENGTH_SHORT).show();
    }
});

题外话：

最新的support包已经解决了fragment嵌套时里层的fragment收不到结果的问题，请及时更新依赖。