Android 5.0输入系统分析之InputReader和InputDispatcher线程启动过程_inputdispatcher::createinputmonitor-优快云博客

本文链接：https://blog.youkuaiyun.com/u013110721/article/details/77548906

Android输入系统工作流程如图（1），InputReader线程不断地从Input Driver中读取原始数据销做处理，放入enqueueInboundEventLocked队例中，InputDispatcher线程不断从enqueueInboundEventLocked队例中取出数据进行处理，把能传给用户的数据放入mInboundQueue队例中，然后最后APP进程从mInboundQueue队例中取出数据进行处理。

首先说明，所有图片来自：http://blog.youkuaiyun.com/jinzhuojun/article/details/41909159 这哥们写的很好，本人刚刚学习android，很多都是参考此文和自已理解写的，一定有不足之处，希望各位大神出来指正。

接下来，先分析InputReader线程和InputDispatcher线程如何启动的？从图（2）的时序图来一步步进行分析

在systemServer.java初始化IMS ，初始化WMS，然后把IMS 作为参数据传给WMS，最后把InputReader线程和InputDispatcher线程start起来

<1> inputManager = new InputManagerService(context);

Slog.i(TAG, "Window Manager");
wm = WindowManagerService.main(context, inputManager,
mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,

!mFirstBoot, mOnlyCore);

ServiceManager.addService(Context.WINDOW_SERVICE, wm);

ServiceManager.addService(Context.INPUT_SERVICE, inputManager); //add service

mActivityManagerService.setWindowManager(wm);

inputManager.setWindowManagerCallbacks(wm.getInputMonitor());

<2> inputManager.start();

先分分析<1>点 inputManager = new InputManagerService(context);

初始化InputManagerService，进入InputManagerService.java的构造函数InputManagerService

public InputManagerService(Context context) {
this.mContext = context;
this.mHandler = new InputManagerHandler(DisplayThread.get().getLooper());

mUseDevInputEventForAudioJack =
context.getResources().getBoolean(R.bool.config_useDevInputEventForAudioJack);
Slog.i(TAG, "Initializing input manager, mUseDevInputEventForAudioJack="
+ mUseDevInputEventForAudioJack);
mPtr = nativeInit(this, mContext, mHandler.getLooper().getQueue());

LocalServices.addService(InputManagerInternal.class, new LocalService());
}

调用了nativeInit，也就是调用（JNI）com_android_server_input_InputManagerService.cpp中nativeInit 函数

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;
}

NativeInputManager* im = new NativeInputManager(contextObj, serviceObj,
messageQueue->getLooper());
im->incStrong(0);
return reinterpret_cast<jlong>(im);
}

在nativeInit 函数中初始化了NativeInputManager，进入NativeInputManager构造函数NativeInputManager

NativeInputManager::NativeInputManager(jobject contextObj, jobject serviceObj, const sp<Looper>& looper) : mLooper(looper), mInteractive(true) {

......

sp<EventHub> eventHub = new EventHub();
mInputManager = new InputManager(eventHub, this, this);
}

可以在NativeInputManager函数中看到初始化了EventHub和InputManager，从中可以知道NativeInputManager层是java世界与c++世界中间桥梁，也就是IMS和InputManager的中间层

EventHub构造函数：

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);

mEpollFd = epoll_create(EPOLL_SIZE_HINT);
LOG_ALWAYS_FATAL_IF(mEpollFd < 0, "Could not create epoll instance. errno=%d", errno);

mINotifyFd = inotify_init();
int result = inotify_add_watch(mINotifyFd, DEVICE_PATH, IN_DELETE | IN_CREATE);
LOG_ALWAYS_FATAL_IF(result < 0, "Could not register INotify for %s. errno=%d",
DEVICE_PATH, errno);

struct epoll_event eventItem;
memset(&eventItem, 0, sizeof(eventItem));
eventItem.events = EPOLLIN;
eventItem.data.u32 = EPOLL_ID_INOTIFY;
result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mINotifyFd, &eventItem);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not add INotify to epoll instance. errno=%d", errno);

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);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake read pipe non-blocking. errno=%d",
errno);

result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking. errno=%d",
errno);

eventItem.data.u32 = EPOLL_ID_WAKE;
result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeReadPipeFd, &eventItem);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not add wake read pipe to epoll instance. errno=%d",
errno);

int major, minor;
getLinuxRelease(&major, &minor);
// EPOLLWAKEUP was introduced in kernel 3.5
mUsingEpollWakeup = major > 3 || (major == 3 && minor >= 5);
}

初始化inotify和epoll，用来监听Input Driver的数据和设备节点变化，后面InputReader线程中会用到。

InputManager构造函数：

InputManager::InputManager(
const sp<EventHubInterface>& eventHub,
const sp<InputReaderPolicyInterface>& readerPolicy,
const sp<InputDispatcherPolicyInterface>& dispatcherPolicy) {
mDispatcher = new InputDispatcher(dispatcherPolicy);
mReader = new InputReader(eventHub, readerPolicy, mDispatcher);
initialize();
}

InputDispatcher和InputReader只是简单初始化。接下来initialize函数

void InputManager::initialize() {
mReaderThread = new InputReaderThread(mReader);
mDispatcherThread = new InputDispatcherThread(mDispatcher);
}

创建了InputDispatcher，InputReader线程。现在<1> inputManager = new InputManagerService(context);跑完了

接下来就是<2> inputManager.start();那么就是调用了InputManagerService.java中start函数

public void start() {
Slog.i(TAG, "Starting input manager");
nativeStart(mPtr);

}

在nativeStart调用了(JNI) com_android_server_input_InputManagerService.cpp中nativeStart函数

static void nativeStart(JNIEnv* env, jclass clazz, jlong ptr) {
NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);

status_t result = im->getInputManager()->start();
if (result) {
jniThrowRuntimeException(env, "Input manager could not be started.");
}
}

在nativeStart函数中调用了InputManager.java的start函数

status_t InputManager::start() {
status_t result = mDispatcherThread->run("InputDispatcher", PRIORITY_URGENT_DISPLAY);
if (result) {
ALOGE("Could not start InputDispatcher thread due to error %d.", result);
return result;
}

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;
}