android inputmanager中事件的传递流程

本文主要是介绍android inputmanager中事件的传递流程，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

涉及文件路径：

frameworks\base\services\core\java\com\android\server\input\InputManagerService.java
frameworks\base\core\java\android\view\InputChannel.java
frameworks\base\core\jni\android_view_InputChannel.cpp
frameworks\base\core\java\android\hardware\input\InputManager.java
frameworks\base\services\core\jni\com_android_server_input_InputManagerService.cpp
frameworks\native\services\inputflinger\InputManager.h
frameworks\native\services\inputflinger\InputManager.cpp
frameworks\native\services\inputflinger\InputReader.h
frameworks\native\services\inputflinger\InputReader.cpp
frameworks\native\services\inputflinger\InputListener.cpp
frameworks\native\services\inputflinger\InputDispatcher.h
system\core\libutils\include\utils\Looper.h
system\core\libutils\Looper.cpp
frameworks\native\services\inputflinger\InputDispatcher.cpp
frameworks\native\libs\input\InputTransport.cpp
frameworks\native\include\input\InputTransport.h
frameworks\base\core\java\android\view\ViewRootImpl.java
frameworks\native\services\inputflinger\EventHub.h
frameworks\native\include\input\InputDevice.h
frameworks\native\services\inputflinger\EventHub.cpp
frameworks\base\services\core\java\com\android\server\wm\WindowManagerService.java
frameworks\base\services\core\java\com\android\server\wm\Session.java
frameworks\base\core\java\android\view\InputEventReceiver.java
frameworks\base\core\jni\android_view_InputEventReceiver.cpp

概述：

android系统输入管理系统inputmanager主要功能就是监听android输入设备，及时将屏幕点击、按键事件、滚动球、鼠标等输入设备产生的输入事件通过转换成java层可使用的事件，比如motionevent，keyevent等将其从底层设备获取出来传递至android系统或者app，然后由系统或者app来做出相应的处理，比如在一个activity中点击了一个控件，屏幕的点击事件会通过inputmanager系统转化成一次触摸事件，然后将其传递至activity，然后activity继续将其传递至该控件，由该控件来做相应处理。

inputmanager系统主要类关系图如下：

主要从五个流程上来分析：
1、inputmanager系统的初始化
2、InputReader读取事件的流程
3、InputDispatcher事件分发的流程
4、java层事件监听器的注册流程
5、事件如何从C层传递至Java层

inputmanager系统的初始化

inputmanagerservice服务在systemserver中启动：

            traceBeginAndSlog("StartInputManagerService");inputManager = new InputManagerService(context);traceEnd();............traceBeginAndSlog("StartInputManager");inputManager.setWindowManagerCallbacks(wm.getInputMonitor());inputManager.start();traceEnd();

InputManagerService服务启动后的流程如下图：

inputmanagerservice初始化方法如下：

    public InputManagerService(Context context) {this.mContext = context;this.mHandler = new InputManagerHandler(DisplayThread.get().getLooper());mUseDevInputEventForAudioJack =context.getResources().getBoolean(R.bool.config_useDevInputEventForAudioJack);//调用native方法的初始化，这个是重点mPtr = nativeInit(this, mContext, mHandler.getLooper().getQueue());......}......public void start() {//开始扫描设备发送事件nativeStart(mPtr);......}

com_android_server_input_InputManagerService.cpp中的方法如下：

static jlong nativeInit(JNIEnv* env, jclass /* clazz */,jobject serviceObj, jobject contextObj, jobject messageQueueObj) {sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);if (messageQueue == NULL) {jniThrowRuntimeException(env, "MessageQueue is not initialized.");return 0;}//初始化NativeInputManagerNativeInputManager* im = new NativeInputManager(contextObj, serviceObj,messageQueue->getLooper());im->incStrong(0);return reinterpret_cast<jlong>(im);
}static void nativeStart(JNIEnv* env, jclass /* clazz */, jlong ptr) {NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);//开始事件的扫描和派发status_t result = im->getInputManager()->start();if (result) {jniThrowRuntimeException(env, "Input manager could not be started.");}
}NativeInputManager::NativeInputManager(jobject contextObj,jobject serviceObj, const sp<Looper>& looper) :mLooper(looper), mInteractive(true) {JNIEnv* env = jniEnv();mContextObj = env->NewGlobalRef(contextObj);mServiceObj = env->NewGlobalRef(serviceObj);{AutoMutex _l(mLock);mLocked.systemUiVisibility = ASYSTEM_UI_VISIBILITY_STATUS_BAR_VISIBLE;mLocked.pointerSpeed = 0;mLocked.pointerGesturesEnabled = true;mLocked.showTouches = false;mLocked.pointerCapture = false;}mInteractive = true;//初始化EventHub和InputManagersp<EventHub> eventHub = new EventHub();mInputManager = new InputManager(eventHub, this, this);
}

EventHub.cpp

EventHub::EventHub(void) :mBuiltInKeyboardId(NO_BUILT_IN_KEYBOARD), mNextDeviceId(1), mControllerNumbers(),mOpeningDevices(0), mClosingDevices(0),mNeedToSendFinishedDeviceScan(false),mNeedToReopenDevices(false), mNeedToScanDevices(true),mPendingEventCount(0), mPendingEventIndex(0), mPendingINotify(false) {acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_ID);//新建epoll对象mEpollFd = epoll_create(EPOLL_SIZE_HINT);//新建notify对象mINotifyFd = inotify_init();//将存储设备点的路径dev/input作为监听对象添加到inotify对象中int result = inotify_add_watch(mINotifyFd, DEVICE_PATH, IN_DELETE | IN_CREATE);//将mINotifyFd作为epoll的一个监控对象struct epoll_event eventItem;memset(&eventItem, 0, sizeof(eventItem));eventItem.events = EPOLLIN;eventItem.data.u32 = EPOLL_ID_INOTIFY;//将对mINotifyFd的监听注册到epoll对象中result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mINotifyFd, &eventItem);int wakeFds[2];result = pipe(wakeFds);LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe.  errno=%d", errno);mWakeReadPipeFd = wakeFds[0];mWakeWritePipeFd = wakeFds[1];result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);eventItem.data.u32 = EPOLL_ID_WAKE;result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeReadPipeFd, &eventItem);int major, minor;getLinuxRelease(&major, &minor);mUsingEpollWakeup = major > 3 || (major == 3 && minor >= 5);
}

在EventHub的构造函数中，它通过INotify与Epoll机制建立起对设备点增删事件及可读状态的监听。INotify是Linux内核所提供的一种文件系统变化通知机制。它可以为应用程序监控文件系统的变化，如文件的新建、删除、读写等等。它有两个基本对象，inotify对象对应一个队列，应用程序可以向inotify对象添加多个监听，当被监听的事件发生时，可以通过read()函数从inotify对象中将事件信息读取出来；而watch对象则用来描述文件系统的变化事件的监听，它是一个二元组，包括监听目标和事件掩码两个元素，监听目标是文件系统的一个路径，可以是文件也可以是文件夹。Epoll可以使用一次等待监听多个描述符的可读/可写状态。

InputManager.cpp

InputManager::InputManager(const sp<EventHubInterface>& eventHub,const sp<InputReaderPolicyInterface>& readerPolicy,const sp<InputDispatcherPolicyInterface>& dispatcherPolicy) {mDispatcher = new InputDispatcher(dispatcherPolicy);//reader的初始化中将mDispatcher作为参数传入mReader = new InputReader(eventHub, readerPolicy, mDispatcher);initialize();
}

从类关系图可知，InputDispatcher继承自InputListenerInterface

void InputManager::initialize() {//初始化两个线程mReaderThread = new InputReaderThread(mReader);mDispatcherThread = new InputDispatcherThread(mDispatcher);
}

status_t InputManager::start() {//启动线程开始派发事件status_t result = mDispatcherThread->run("InputDispatcher", PRIORITY_URGENT_DISPLAY);if (result) {ALOGE("Could not start InputDispatcher thread due to error %d.", result);return result;}//启动线程开始读取设备输入事件result = mReaderThread->run("InputReader", PRIORITY_URGENT_DISPLAY);if (result) {ALOGE("Could not start InputReader thread due to error %d.", result);mDispatcherThread->requestExit();return result;}return OK;
}

InputReader读取事件的流程

事件读取流程如下图：

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