Android事件分发的事件由来原理分析
目录
- Andriod事件分发的事件从何而来
- 调用WMS中的成员mInputManager
- 调用的mNative的方法
- 看看InputManager怎么初始化
- createInputChannel干了3件事
- 首先看下openInputChannelPair
- 回到createInputChannel中
Andriod事件分发的事件从何而来
上一篇最后留下了一个疑问,WMS的事件是哪里来的?
注册事件回调是通过mWindowSession.addToDisplayAsUser来实现的,这是一个Binder调用实际调用的是frameworks/base/services/core/java/com/android/server/wm/Session.java这个类。
//frameworks/base/services/core/java/com/android/server/wm/Session.java @Override public int addToDisplayAsUser(IWindow window, WindowManager.LayoutParams attrs, int viewVisibility, int displayId, int userId, InsetsVisibilities requestedVisibilities, InputChannel outInputChannel, InsetsState outInsetsState, InsetsSourceControl[] outActiveControls, Rect outAttachedFrame, float[] outSizeCompatScale) { return mService.addWindow(this, window, attrs, viewVisibility, displayId, userId, requestedVisibilities, outInputChannel, outInsetsState, outActiveControls, outAttachedFrame, outSizeCompatScale); }
这里的mService就是WMS.调用的就是WMS的addWindow,addWindow方法很长,其中与事件相关的就两行
//frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java ...... final WindowState win = new WindowState(this, session, client, token, parentWindow,appOp[0], attrs, viewVisibility, session.mUid, userId,session.mCanAddInternalSystemWindow); win.openInputChannel(outInputChannel);
//frameworks/base/services/core/java/com/android/server/wm/WindowState.java void openInputChannel(InputChannel outInputChannel) { if (mInputChannel != null) { throw new IllegalStateException("Window already has an input channel."); } String name = getName(); mInputChannel = mWmService.mInputManager.createInputChannel(name); mInputChannelToken = mInputChannel.getToken(); mInputWindowHandle.setToken(mInputChannelToken); mWmService.mInputToWindowMap.put(mInputChannelToken, this); if (outInputChannel != null) { //将native创建的InputChannel复制给参数outInputChannel mInputChannel.copyTo(outInputChannel); } else { // If the window died visible, we setup a fake input channel, so that taps // can still detected by input monitor channel, and we can relaunch the app. // Create fake event receiver that simply reports all events as handled. mDeadWindowEventReceiver = new DeadWindowEventReceiver(mInputChannel); } }
调用WMS中的成员mInputManager
调用了WMS中的成员mInputManager来注册了InputChannel,mInputManager是一个InputManagerService。
这下就对了,事件从InputManagerService中来很合理。
public InputChannel createInputChannel(String name) { return mNative.createInputChannel(name); }
调用的mNative的方法
这个对象是在InputManagerService创建的时候初始化的
public InputManagerService(Context context) { this(new Injector(context, DisplayThread.get().getLooper())); } @VisibleForTesting InputManagerService(Injector injector) { // The static association map is accessed by both java and native code, so it must be // initialized before initializing the native service. mStaticAssociations = loadStaticInputPortAssociations(); mContext = injector.getContext(); mHandler = new InputManagerHandler(injector.getLooper()); mNative = injector.getNativeService(this); .... } //frameworks/base/services/core/java/com/android/server/input/NativeInputManagerService.java NativeInputManagerService getNativeService(InputManagerService service) { return new NativeInputManagerService.NativeImpl(service, mContext, mLooper.getQueue()); }
最终返回的是一个NativeImpl实例。字面意思就知道了,这是一个Native方法的实现,createInputChannel来到了native层。
//frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp base::Result<std::unique_ptr<InputChannel>> NativeInputManager::createInputChannel( const std::string& name) { ATRACE_CALL(); return mInputManager->getDispatcher().createInputChannel(name); }
调用了mInputManager的getDispatcher函数看名字就知道应该有个变量mDispatcher,查看mInputManager是怎么创建的可以发现是在NativeInputManager创建的时候初始化的
InputManager* im = new InputManager(this, this); mInputManager = im;
看看InputManager怎么初始化
InputManager::InputManager( const sp<InputReaderPolicyInterface>& readerPolicy, const sp<InputDispatcherPolicyInterface>& dispatcherPolicy) { mDispatcher = createInputDispatcher(dispatcherPolicy); mClassifier = std::make_unique<InputClassifier>(*mDispatcher); mBlocker = std::make_unique<UnwantedInteractionBlocker>(*mClassifier); mReader = createInputReader(readerPolicy, *mBlocker); }
这里就出现了重要的两个类InputDispatcher和InputReader,createInputChanne方法l最终调用到了InputDispatcher中的createInputChannel。
//frameworks/native/services/inputflinger/dispatcher/InputDispatcher.cpp Result<std::unique_ptr<InputChannel>> InputDispatcher::createInputChannel(const std::string& name) { if (DEBUG_CHANNEL_CREATION) { ALOGD("channel '%s' ~ createInputChannel", name.c_str()); } std::unique_ptr<InputChannel> serverChannel; std::unique_ptr<InputChannel> clientChannel; //调用创建了一个serverChannel和一个clientChannel status_t result = InputChannel::openInputChannelPair(name, serverChannel, clientChannel); if (result) { return base::Error(result) << "Failed to open input channel pair with name " << name; } { // acquire lock std::scoped_lock _l(mLock); const sp<IBinder>& token = serverChannel->getConnectionToken(); int fd = serverChannel->getFd(); sp<Connection> connection = new Connection(std::move(serverChannel), false /*monitor*/, mIdGenerator); if (mConnectionsByToken.find(token) != mConnectionsByToken.end()) { ALOGE("Created a new connection, but the token %p is already known", token.get()); } mConnectionsByToken.emplace(token, connection); std::function<int(int events)> callback = std::bind(&InputDispatcher::handleReceiveCallback, this, std::placeholders::_1, token); mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, new LooperEventCallback(callback), nullptr); } // release lock // Wake the looper because some connections have changed. mLooper->wake(); return clientChannel; }
createInputChannel干了3件事
- 首先使用openInputChannelPair创建了2个InputChannel,一个clientChannel和一个serverChannel
- 将serverChannel封装成connection,并放入成员变量mConnectionsByToken中管理,这样在事件到来的时候就可以使用connection向客户端发送事件了
- 利用Looper持续监听serverChannel,事件处理的回调消息会就到InputDispatcher::handleReceiveCallback回调,最后把clientChannel返回给客户端,也就是最初在WMS中得到的InputChannel。
首先看下openInputChannelPair
//frameworks/native/libs/input/InputTransport.cpp status_t InputChannel::openInputChannelPair(const std::string& name, std::unique_ptr<InputChannel>& outServerChannel, std::unique_ptr<InputChannel>& outClientChannel) { int sockets[2]; //真正创建了socket if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) { status_t result = -errno; ALOGE("channel '%s' ~ Could not create socket pair. errno=%s(%d)", name.c_str(), strerror(errno), errno); outServerChannel.reset(); outClientChannel.reset(); return result; } //设置了socket传输的大小为32k int bufferSize = SOCKET_BUFFER_SIZE; setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize)); setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize)); setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize)); setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize)); sp<IBinder> token = new BBinder(); std::string serverChannelName = name + " (server)"; android::base::unique_fd serverFd(sockets[0]); outServerChannel = InputChannel::create(serverChannelName, std::move(serverFd), token); std::string clientChannelName = name + " (client)"; android::base::unique_fd clientFd(sockets[1]); outClientChannel = InputChannel::create(clientChannelName, std::move(clientFd), token); return OK; }
熟悉Linux的话就知道socketpair创建了一对双向的socket,往socket[0]中写能从socket[1]读,反向也是一样,分别创建了outServerChannel和outClientChannel,两个InputChannel有着同一个BBinder作为token。
回到createInputChannel中
const sp<IBinder>& token = serverChannel->getConnectionToken(); int fd = serverChannel->getFd();//拿到socket fd sp<Connection> connection = new Connection(std::move(serverChannel), false /*monitor*/, mIdGenerator); if (mConnectionsByToken.find(token) != mConnectionsByToken.end()) { ALOGE("Created a new connection, but the token %p is already known", token.get()); } mConnectionsByToken.emplace(token, connection); std::function<int(int events)> callback = std::bind(&InputDispatcher::handleReceiveCallback, this, std::placeholders::_1, token); mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, new LooperEventCallback(callback), nullptr);
这里将创建的serverChannel封装成了connection,同时用token作为key,存到了mConnectionsByToken中,这样就可以利用token来快速找到serverChannel封装的connection。最后监听serverChannel的fd,有事件时回调给InputDispatcher::handleReceiveCallback方法的最后把创建的clientChannel返回给了客户端,就是开头的WMS中。这样在WMS就也能通过clientChannel来获取事件了。
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