針對上篇《過時(shí)的OnActivityResult一》厚棵，本篇進(jìn)行源碼解析：

先來看一下在Activity中啟動launcher之后是怎么實(shí)現(xiàn)這種功能的

調(diào)用ComponentActivity中的registerForActivityResult，該方法返回一個(gè)ActivityResultLauncher用于啟動Intent

public final <I, O> ActivityResultLauncher<I> registerForActivityResult(
        @NonNull final ActivityResultContract<I, O> contract,
        @NonNull final ActivityResultRegistry registry,
        @NonNull final ActivityResultCallback<O> callback) {
    return registry.register(
            "activity_rq#" + mNextLocalRequestCode.getAndIncrement(), this, contract, callback);
}

由于沒有自定義ActivityResultRegistry,所以這里使用的是ComponentActivity中的mActivityResultRegistry,調(diào)用了ActivityResultRegistry中的register

register則使用了lifecycleOwner實(shí)現(xiàn)了自動解綁功能愈污，然后返回了一個(gè)ActivityResultLauncher,并調(diào)用了invoke方法

public final <I, O> ActivityResultLauncher<I> register() {
        // 注冊一個(gè)requestCode并保存回調(diào),這里的回調(diào)就是在onActivityResult攔截的時(shí)候取的
        final int requestCode = registerKey(key);
        mKeyToCallback.put(key, new CallbackAndContract<>(callback, contract));
        // 這里最終返回的是我們需要的ActivityResultLauncher怠惶，并調(diào)用了ComponentActivity中mActivityResultRegistry的invoke
        return new ActivityResultLauncher<I>() {
            @Override
            public void launch(I input, @Nullable ActivityOptionsCompat options) {
                invoke(requestCode, contract, input, options);
            }

            @Override
            public void unregister() {
                ActivityResultRegistry.this.unregister(key);
            }
        };
}

這個(gè)時(shí)候回到ComponentActivity的mActivityResultRegistry看下源碼就知道是怎么一回事了涨缚，該方法先判斷了action是否為權(quán)限或者支付，最后調(diào)用的startActivityForResult

private ActivityResultRegistry mActivityResultRegistry = new ActivityResultRegistry() {
        @Override
        public <I, O> void invoke() {
            ComponentActivity activity = ComponentActivity.this;
            Intent intent = contract.createIntent(activity, input);
            if (ACTION_REQUEST_PERMISSIONS.equals(intent.getAction())) {
                // requestPermissions path  權(quán)限處理
            } else if (ACTION_INTENT_SENDER_REQUEST.equals(intent.getAction())) {
                //google支付
            } else {
                // 啟動activity最終調(diào)用的是這里
                ActivityCompat.startActivityForResult(activity, intent, requestCode, options != null ? options.toBundle() : null);
            }
        }
 };

具體流程大概是這個(gè)樣子策治，再來看下是如何攔截onActivityResult的

ActivityResultRegistry攔截了onActivityResult,onRequestPermissionsResult同理脓魏，dispatchResult方法判斷了是否需要攔截,根據(jù)在調(diào)用register的時(shí)候保存的registerkey來判斷

protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    //處理onActivityResult如果不是launcher啟動的則還是走onActivityResult
    //不過這里已經(jīng)標(biāo)記為過時(shí)
    if (!mActivityResultRegistry.dispatchResult(requestCode, resultCode, data)) {
        super.onActivityResult(requestCode, resultCode, data);
    }
}

然后拿出mKeyToCallback中保存對應(yīng)requestCode的回調(diào)ActivityResultCallback，這個(gè)時(shí)候調(diào)用ActivityResultCallback的onActivityResult通惫，這樣就能拿到對應(yīng)的數(shù)據(jù)和狀態(tài)

public final boolean dispatchResult(int requestCode, int resultCode, @Nullable Intent data) {
    String key = mRcToKey.get(requestCode);
    if (key == null) {
        //使用的startActivityForResult
        return false;
    }
    doDispatch(key, resultCode, data, mKeyToCallback.get(key));
    return true;
}

//這里就比較簡單了,獲取回調(diào)之后返回parseResult生成的類數(shù)據(jù)
private <O> void doDispatch(String key, int resultCode, @Nullable Intent data, @Nullable CallbackAndContract<O> callbackAndContract) {
    if (callbackAndContract != null && callbackAndContract.mCallback != null) {
        ActivityResultCallback<O> callback = callbackAndContract.mCallback;
        ActivityResultContract<?, O> contract = callbackAndContract.mContract;
        //parseResult返回的什么這里就獲取的什么
        callback.onActivityResult(contract.parseResult(resultCode, data));
    } else {
        mPendingResults.putParcelable(key, new ActivityResult(resultCode, data));
    }
}

fragment也是先拿到mActivityResultRegistry然后還是走的Activity流程

public final <I, O> ActivityResultLauncher<I> registerForActivityResult(
        @NonNull final ActivityResultContract<I, O> contract,
        @NonNull final ActivityResultCallback<O> callback) {
    return prepareCallInternal(contract, new Function<Void, ActivityResultRegistry>() {
        @Override
        public ActivityResultRegistry apply(Void input) {
            //返回了ComponentActivity的ActivityResultRegistry
            if (mHost instanceof ActivityResultRegistryOwner) {
                return ((ActivityResultRegistryOwner) mHost).getActivityResultRegistry();
            }
            return requireActivity().getActivityResultRegistry();
        }
    }, callback);
}