12. 输入系统_APP跟输入系统建立联系_InputChannel和Connection
核心: socketpair // 第9课第3节_输入系统_必备Linux编程知识_任意进程双向通信(scoketpair+binder)
对于每个APP在WindowManagerService中都有个WindowState与之对应,当新建一个APP的时候通过binder系统调用addToDisplay把自己告诉给WindowManagerService,同时会导致addWindow被调用,其会创建WindowState来表示这个应用程序,并创建一个socketpair得到两个文件句柄fd0和fd1,同时把fd1返回给应用程序,把fd0封装成Inputchannel,这个Inputchannel会放入到WindowState中,也会通过registerInputchannel注册给InputDispatcher,在InputDispatcher中会根据Inputchannel来构造一个Connection,把这个创建出来的Connection放入KeyedVector(KeyedVector<int,sp<Connection>> mConnectionsByFd),这个InputDispatcher得到数据后放入某个Connection.Inputchannel.fd0中,APP端从fd1取得数据;APP在收到返回的fd1后,把其封装成Inputchannel,在把其封装成WindowInputEventReceiver,最后把fd1放入Looper中,使用epoll来查询等待。
对于每个能接受输入事件的应用程序,其在InputDispatcher中都有对应的connection,InputDispatcher需要把数据发送给应用程序的时候,需要找出当前在屏幕最前面的是哪个应用程序,然后找到他的connection,把数据输入他的fd就可以
InputReader线程、InputDispatcher线程、WindowManagerService线程都属于SystemServer进程中,线程可以直接通讯,不需要binder
应用程序调用:
handleResumeActivity
ViewManager wm =a.getWindowManager()//这个WindowManager和上面说的WindowManagerService不是一个东西
wm.addView(decor,l);
mGlobal.addView()
root = new ViewRootlmpl()
root.setView()
mWindowSession.addToDisplay(...,mInputChannel)//该函数是分界线,下面的内容是在WindowManagerService线程中执行,前面的都是在应用程序中执行的,mWindowSession是一个远程服务的引用,mInputChannel包含有返回的文件句柄fd1
mRemote.transact(Stub.TRANSACTION_addToDisplay,...)
onTransact
addToDisplay
addWindow
InputChannel[] inputChannels = InputChannel.openInputChannelPair(name)//得到fd0和fd1
nativeOpenInputChannelPair
android_view_InputChannel_nativeOpenInputChannelPair
openInputChannelPair
socketpair
win.setInputChannel(inputChannels[0])
inputChannels[1].transferTo(outInputChannel)
mInputManager.registerInputChannel //把inputChannels[1]告诉InputDispatcher,WindowManagerService与InputDispatcher同属一个进程,所有可以直接调用
nativeRegisterInputChannel
im->registerInputChannel
registerInputChannel
connection = new Connection(inputChannel,inputWindowHandle,monitor)
int fd = inputChannel->getFd()
mConnectionByFd.add(fd,connection);
mLooker->addFd(fd,0,ALOOPER_EVENT_INPUT,....)
_arg6.writeToParcel
parcel->writeDupFileDescriptor(inputChannel->getFd())//把fd1写入binder驱动
outInputChannel.readFromParcel(_reply)
int rawFd = parcel->readFileDescriptor();//binder驱动中读到fd1
int dupFd = dup(rawFd);
InputChannel* inputChannel = new InputChannel(name, dupFd);
NativeInputChannel* nativeInputChannel = new NativeInputChannel(inputChannel);
android_view_InputChannel_setNativeInputChannel(env, obj, nativeInputChannel);
mInputEventReceiver = new WindowInputEventReceiver()
InputEventReceiver
nativeInit
receiver = new NativeInputEventReceiver
receiver->initialize()
setFdEvents
mMessageQueue->getLooper()->addFd(fd,0,events,this,NULL)
13. 输入系统_Dispatcher线程_分发dispatch
dispatch线程中有mConnectionsByFd,其中有一些列的connection,connection中有inputchannel.fd0,通过socketpair与APP的fd1通讯
分发的步骤(具体情景分析见uml图中的dispatch_input_event)
(1)查找目标
向WindowManagerService查询当前Window获得对应的Connection
(2)把输入事件放入Connection的队列outboundQueue
(3)从队列中取出事件构造为InputMessage发送