public final <I, O> ActivityResultLauncher register(
@NonNull final String key,
@NonNull final LifecycleOwner lifecycleOwner,
@NonNull final ActivityResultContract<I, O> con
tract,
@NonNull final ActivityResultCallback callback) {
Lifecycle lifecycle = lifecycleOwner.getLifecycle();
//每个请求的key也不一样，根据key生成一个唯一的requestCode
final int requestCode = registerKey(key);
//把lifecycle和observer统一封装到LifecycleContainer中
LifecycleContainer lifecycleContainer = mKeyToLifecycleContainers.get(key);
if (lifecycleContainer == null) {
lifecycleContainer = new LifecycleContainer(lifecycle);
}
LifecycleEventObserver observer = new LifecycleEventObserver() {
@Override
public void onStateChanged(
@NonNull LifecycleOwner lifecycleOwner,
@NonNull Lifecycle.Event event) {
if (Lifecycle.Event.ON_START.equals(event)) {//处理回调
mKeyToCallback.put(key, new CallbackAndContract<>(callback, contract));
if (mParsedPendingResults.containsKey(key)) {
@SuppressWarnings(“unchecked”)
final O parsedPendingResult = (O) mParsedPendingResults.get(key);
mParsedPendingResults.remove(key);
callback.onActivityResult(parsedPendingResult);
}
//从bundle中获取结果
final ActivityResult pendingResult = mPendingResults.getParcelable(key);
if (pendingResult != null) {
mPendingResults.remove(key);
//把结果回调给调用者
callback.onActivityResult(contract.parseResult(
pendingResult.getResultCode(),
pendingResult.getData()));
}
} else if (Lifecycle.Event.ON_STOP.equals(event)) {
mKeyToCallback.remove(key);//stop时移除
} else if (Lifecycle.Event.ON_DESTROY.equals(event)) {
unregister(key);//destory时注销
}
}
};
//添加观察者
lifecycleContainer.addObserver(observer);
mKeyToLifecycleContainers.put(key, lifecycleContainer);
//返回ActivityResultLauncher对象
return new ActivityResultLauncher() {
@Override
public void launch(I input, @Nullable ActivityOptionsCompat options) {
mLaunchedKeys.add(key);
//ActivityResultRegistry的onLaunch，抽象方法，在ComponentActivity内实现
onLaunch(requestCode, contract, input, options);
}
public void unregister() {
ActivityResultRegistry.this.unregister(key);
}
public ActivityResultContract<I, ?> getContract() {
return contract;
}
};
}
2.launch
ActivityResultRegistry的onLaunch是一个抽象方法，在ComponentActivity内实现。首先会检查contract是否能获取同步结果，如果能，则直接分发处理。比如权限申请，我前面已经获取了权限，直接可以通过getSynchronousResult查询是否有权限。有直接返回true，不再通过requestPermissions去做申请权限。
在通过contract获取Intent，按Intent分为三种情况处理，第一种，权限申请，通过requestPermissions去申请权限，第二种处理INTENT_SENDER，和startIntentSenderForResult类似。第三种，处理其它问题，通过startActivityForResult启动Activity
public <I, O> void onLaunch(
final int requestCode,
@NonNull ActivityResultContract<I, O> contract,
I input,
@Nullable ActivityOptionsCompat options) {
ComponentActivity activity = ComponentActivity.this;
//如果能直接拿到结果，直接分发处理了。
final ActivityResultContract.SynchronousResult synchronousResult =
contract.getSynchronousResult(activity, input);
if (synchronousResult != null) {
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
dispatchResult(requestCode, synchronousResult.getValue());
}
});
return;
}
// 根据协定创建Intent对象
Intent intent = contract.createIntent(activity, input);
Bundle optionsBundle = null;
// If there are any extras, we should defensively set the classLoader
if (intent.getExtras() != null && intent.getExtras().getClassLoader() == null) {
intent.setExtrasClassLoader(activity.getClassLoader());
}
if (intent.hasExtra(EXTRA_ACTIVITY_OPTIONS_BUNDLE)) {
optionsBundle = intent.getBundleExtra(EXTRA_ACTIVITY_OPTIONS_BUNDLE);
intent.removeExtra(EXTRA_ACTIVITY_OPTIONS_BUNDLE);
} else if (options != null) {
optionsBundle = options.toBundle();
}
//处理权限
if (ACTION_REQUEST_PERMISSIONS.equals(intent.getAction())) {
// requestPermissions path
String[] permissions = intent.getStringArrayExtra(EXTRA_PERMISSIONS);
if (permissions == null) {
permissions = new String[0];
}
ActivityCompat.requestPermissions(activity, permissions, requestCode);
} else if (ACTION_INTENT_SENDER_REQUEST.equals(intent.getAction())) {
//处理StartIntentSenderForResult
IntentSenderRequest request =
intent.getParcelableExtra(EXTRA_INTENT_SENDER_REQUEST);
try {
// startIntentSenderForResult path
ActivityCompat.startIntentSenderForResult(activity, request.getIntentSender(),
requestCode, request.getFillInIntent(), request.getFlagsMask(),
request.getFlagsValues(), 0, optionsBundle);
} catch (final IntentSender.SendIntentException e) {
}
} else {
//其它普通问题启动Activity
ActivityCompat.startActivityForResult(activity, intent, requestCode, optionsBundle);
}
}
3.结果回调
在ComponentActivity中，onActivityResult和onRequestPermissionsResult方法会先被ActivityResultRegistry的dispatchResult方法拦截，如果它能处理，则不再调用Activity的方法。
dispatchResult会调用doDispatch来处理结果，这有两种情况，通过key从mKeyToCallback中获取callbackAndContract对象，如果不为空，则直接回调结果。比如权限申请，不会走ON_STOP事件，mKeyToCallback不会被清除，这里就不会为空。如果为空则把结果放到mPendingResults这个Bundle对象中，和前面的ON_START事件对应起来，从mPendingResults取出结果，回调结果。
-ComponentActivity.java
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
if (!mActivityResultRegistry.dispatchResult(requestCode, resultCode, data)) {
super.onActivityResult(requestCode, resultCode, data);
}
}
public void onRequestPermissionsResult(
int requestCode,
@NonNull String[] permissions,
@NonNull int[] grantResults) {
if (!mActivityResultRegistry.dispatchResult(requestCode, Activity.RESULT_OK, new Intent()
.putExtra(EXTRA_PERMISSIONS, permissions)
.putExtra(EXTRA_PERMISSION_GRANT_RESULTS, grantResults))) {
if (Build.VERSION.SDK_INT >= 23) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}
}
}
- ActivityResultRegistry.java
public final boolean dispatchResult(int requestCode, int resultCode, @Nullable Intent data) {
String key = mRcToKey.get(requestCode);
if (key == null) {
return false;
}
mLaunchedKeys.remove(key);
doDispatch(key, resultCode, data, mKeyToCallback.get(key));
return true;
}
private void doDispatch(String key, int resultCode, @Nullable Intent data,
@Nullable CallbackAndContract callbackAndContract) {
callbackAndContract不为空则直接回调即可
if (callbackAndContract != null && callbackAndContract.mCallback != null) {
ActivityResultCallback callback = callbackAndContract.mCallback;
ActivityResultContract<?, O> contract = callbackAndContract.mContract;
callback.onActivityResult(contract.parseResult(resultCode, data));
act callbackAndContract) {
callbackAndContract不为空则直接回调即可
if (callbackAndContract != null && callbackAndContract.mCallback != null) {
ActivityResultCallback callback = callbackAndContract.mCallback;
ActivityResultContract<?, O> contract = callbackAndContract.mContract;
callback.onActivityResult(contract.parseResult(resultCode, data));