兩個類，讓你再也不用實現onActivityResult()

天之界線2010發表於2019-03-04

當我們知道fragment僅僅可以收到自己請求的回撥後，我們就可以用它來解耦activity中onActivityResult的邏輯了。一般情況下，如果一個activity中多個回撥結果的話，onActivityResult()中會有各種case判斷，並且這種設計也打斷了流式寫法。那麼我們索性建立一個無UI的fragment做精準的接收器，這樣就可以再也不寫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);
        }
    }

}
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請求封裝類：

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);
    }
}
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傳送請求和監聽請求的程式碼：

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();
    }
});
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題外話：

最新的support包已經解決了fragment巢狀時裡層的fragment收不到結果的問題，請及時更新依賴。

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