Android中InputManagerService里的InputReader和inputDispatcher

2023年8月5日 509次阅读来源: vastyh

最近工作中遇到InputManagerService相关的问题，所以将InputReader和InputDispatcher看了一遍，水平有限，有的也没有理解。

这是input的中重要的两个类，这两个类由对应的两个线程来管理InputReaderThread和InputDispatcherThread，他们都是使用C++实现的。首先简单介绍下InputManagerService的实现。

InputReaderThread InputDispatcherThread Binder(InputManagerService)… Proxy…

负责从/dev/input/下读取输入事件，之后将input_event进入队列，

通知inputDispatcherThread 处理得到输入事件后，根据当前inputChannel情况，进行发送负责对InputReader和InputDispatcher的管理，提供接口供其他进程访问，如插入一个输入事件，注册一个inputChannel灯外部调用，如果input作为一个模块的话，这个接口是真正对外开放的

1 俩线程的启动

JAVA: InputManagerService.nativeInt () ->C++:NativeInputManager()->C++:InputManager()->C++:InputManager->initialize():如下代码所示：

48：void InputManager::initialize() {

49： mReaderThread = new InputReaderThread(mReader);

50： mDispatcherThread = new InputDispatcherThread(mDispatcher);

51：}

注意在本文之后inputReaderThread简称R线程，inputDispatcherThread简称D线程。

2 InputReader的执行

重要的函数：InputReader->loopOnce();，R线程是不断地在这个函数里循环。下面就看这个函数做了什么，首先介绍几个不重要的成员变量：

mGeneration:这个变量是标识输入设备的变化的，也就是说当设备新建，添加，删除时就会执行loopOnce()中的这段代码：

if (oldGeneration != mGeneration) {

inputDevicesChanged = true;

getInputDevicesLocked(inputDevices);

}

} // release lock

// Send out a message that the describes the changed input devices.

if (inputDevicesChanged) {

mPolicy->notifyInputDevicesChanged(inputDevices);

}

size_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);

当调用这个函数时，如果有事件发生，count>0, 事件存储在mEventBuffer中。

mEventBuffer：这是存储时间的缓冲。

下面就是重要级的函数，对事件的处理processEventsLocked(mEventBuffer, count);

processEventsLocked->processEventsForDeviceLocked->device->process(rawEvents, count)->mapper->process(rawEvent);

mDevices: 每个输入设备的对象，每个输入设备对应一个process去处理它自己的事件。

mMappers:每个输入设备可能对应不同输入类型，这就需要要mMappers去处理，在mMapers->process中通过notify机制去通知D线程处理输入。

3 InputDispatcher:

InputDispatcher->dispatchOnce()->dispatchOnceInnerLocked:

mPendingEvent:当前需要处理的的事件，如果没有就从mInboundQueue中取。

mInboundQueue:InputDispatcher的事件队列，R线程负责进队列，D进程出队列处理事件。

mTouchState: 表示当前时间处理的状态。

当mPendingEvent的事件需要派发时，如下代码所示：

switch (mPendingEvent->type) {

case EventEntry::TYPE_CONFIGURATION_CHANGED: {

ConfigurationChangedEntry* typedEntry =

static_cast<ConfigurationChangedEntry*>(mPendingEvent);

done = dispatchConfigurationChangedLocked(currentTime, typedEntry);

dropReason = DROP_REASON_NOT_DROPPED; // configuration changes are never dropped

break;

}

case EventEntry::TYPE_DEVICE_RESET: {

DeviceResetEntry* typedEntry =

static_cast<DeviceResetEntry*>(mPendingEvent);

done = dispatchDeviceResetLocked(currentTime, typedEntry);

dropReason = DROP_REASON_NOT_DROPPED; // device resets are never dropped

break;

}

case EventEntry::TYPE_KEY: {

KeyEntry* typedEntry = static_cast<KeyEntry*>(mPendingEvent);

if (isAppSwitchDue) {

if (isAppSwitchKeyEventLocked(typedEntry)) {

resetPendingAppSwitchLocked(true);

isAppSwitchDue = false;

} else if (dropReason == DROP_REASON_NOT_DROPPED) {

dropReason = DROP_REASON_APP_SWITCH;

}

if (dropReason == DROP_REASON_NOT_DROPPED

&& isStaleEventLocked(currentTime, typedEntry)) {

dropReason = DROP_REASON_STALE;

}

if (dropReason == DROP_REASON_NOT_DROPPED && mNextUnblockedEvent) {

dropReason = DROP_REASON_BLOCKED;

}

done = dispatchKeyLocked(currentTime, typedEntry, &dropReason, nextWakeupTime);

break;

}

case EventEntry::TYPE_MOTION: {

MotionEntry* typedEntry = static_cast<MotionEntry*>(mPendingEvent);

if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) {

dropReason = DROP_REASON_APP_SWITCH;

}

if (dropReason == DROP_REASON_NOT_DROPPED

&& isStaleEventLocked(currentTime, typedEntry)) {

dropReason = DROP_REASON_STALE;

}

if (dropReason == DROP_REASON_NOT_DROPPED && mNextUnblockedEvent) {

dropReason = DROP_REASON_BLOCKED;

}

done = dispatchMotionLocked(currentTime, typedEntry,

&dropReason, nextWakeupTime);

break;

}

default:

ALOG_ASSERT(false);

break;

}

if (done) {

if (dropReason != DROP_REASON_NOT_DROPPED) {

dropInboundEventLocked(mPendingEvent, dropReason);

}

releasePendingEventLocked();

*nextWakeupTime = LONG_LONG_MIN; // force next poll to wake up immediately

}

bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) {

bool needWake = mInboundQueue.isEmpty();

mInboundQueue.enqueueAtTail(entry);

traceInboundQueueLengthLocked();

switch (entry->type) {

case EventEntry::TYPE_KEY: {

// Optimize app switch latency.

// If the application takes too long to catch up then we drop all events preceding

// the app switch key.

KeyEntry* keyEntry = static_cast<KeyEntry*>(entry);

if (isAppSwitchKeyEventLocked(keyEntry)) {

if (keyEntry->action == AKEY_EVENT_ACTION_DOWN) {

mAppSwitchSawKeyDown = true;

} else if (keyEntry->action == AKEY_EVENT_ACTION_UP) {

if (mAppSwitchSawKeyDown) {

#if DEBUG_APP_SWITCH

ALOGD(“App switch is pending!”);

#endif

mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;

mAppSwitchSawKeyDown = false;

needWake = true;

}

break;

}

case EventEntry::TYPE_MOTION: {

// Optimize case where the current application is unresponsive and the user

// decides to touch a window in a different application.

// If the application takes too long to catch up then we drop all events preceding

// the touch into the other window.

MotionEntry* motionEntry = static_cast<MotionEntry*>(entry);

if (motionEntry->action == AMOTION_EVENT_ACTION_DOWN

&& (motionEntry->source & AINPUT_SOURCE_CLASS_POINTER)

&& mInputTargetWaitCause == INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY

&& mInputTargetWaitApplicationHandle != NULL) {

int32_t x = int32_t(motionEntry->pointerCoords[0].

getAxisValue(AMOTION_EVENT_AXIS_X));

int32_t y = int32_t(motionEntry->pointerCoords[0].

getAxisValue(AMOTION_EVENT_AXIS_Y));

sp<InputWindowHandle> touchedWindowHandle = findTouchedWindowAtLocked(x, y);

if (touchedWindowHandle != NULL

&& touchedWindowHandle->inputApplicationHandle

!= mInputTargetWaitApplicationHandle) {

// User touched a different application than the one we are waiting on.

// Flag the event, and start pruning the input queue.

mNextUnblockedEvent = motionEntry;

needWake = true;

}

break;

}

这些是处理事件的核心，我们就拿TYPE_MOTION举例，

dispatchMotionLocked->

findTouchedWindowTargetsLocked //填充inputTargets，是否有touchedWindowTarget需要事件

addMonitoringTargetsLocked //加入monitoringTarget

dispatchEventLocked -> //对inputTarget中的每个window进行派发事件

prepareDispatchCycleLocked->

enqueueDispatchEntriesLocked->

connection->outboundQueue.enqueueAtTail(dispatchEntry);

dispatchMotionLocked还是蛮复杂的，很多地方我也没弄明白。看代码话说windowmanagerService通过setInputWindows去填充InputDispacther的mWindowHandles,这是和所有window交流的根源，之后InputDispatcher填充inputTarget, 创建mConntionFd, 与需要input的window进行连接。

    原文作者：vastyh
    原文地址: https://blog.csdn.net/vastyh/article/details/8902162
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