概述

Android 输入系统的工作原理概括来说，内核将原始事件写入到设备节点中，InputReader 不断地通过 EventHub 将原始事件取出来并翻译加工成 Android 输入事件，然后交给 InputDispatcher。

InputDispatcher 根据 WMS 提供的窗口信息将事件交给合适的窗口。窗口的 ViewRootImpl 对象再沿着控件树将事件派发给感兴趣的控件。控件对其收到的事件作出响应，更新自己的画面、执行特定的动作
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概念解释

InputManagerService（IMS）：Android 系统服务，分为 Java 层和 Native 层两部分，Java 层负责与 WMS 通信，而 Native 层则是 InputReader 和 InputDispatcher 两个输入系统关键组件的运行容器；
WindowManagerService（WMS）：它并不是输入系统的一员，新建窗口时，WMS 为新窗口和 IMS 创建了事件传递所用的通道，会将窗口的可点击区域，焦点窗口等信息实时更新到 IMS 的 InputDispatcher 中，使得 InputDispatcher 可以正确将事件派发到指定窗口；
EventHub：直接访问所有的设备节点，通过 getEvents() 函数将所有输入系统相关的待处理的底层事件返回给使用者，包括原始输入事件，设备节点的增删等；
InputReader：运行在一个独立的线程中，负责管理输入设备的列表和配置，以及进行输入事件的加工处理，它通过其线程循环不断地通过 getEvents() 函数从 EventHub 中将事件取出并进行处理，对于设备节点的增删事件，它会更新输入设备列表与配置；对于原始输入事件，InputReader对其进行翻译，组装，封装为包含更多信息，更多可读性的输入事件，然后交给InputDispatcher进行派发；
InputDispatcher：运行于一个独立的线程中，InputDispatcher 中保管来自 WMS 的所有窗口的信息，收到 InputReader 的输入事件后，会在其保管的窗口中寻找合适的窗口，并将事件派发给此窗口；
ViewRootImpl：对某些窗口，如 SurfaceView 的窗口来说，窗口就是输入事件派发的终点，而对其他的如Activity，对话框等使用了 Android 控件系统的窗口来说，输入事件的终点是控件；
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Input 系统流程

服务端

Input 系统初始化 IMS

SystemServer中的 ServerThread 线程中启动 InputManagerService

创建 IMS 对象
1. 创建 NativeInputManager 对象，此对象将是 Native 层组件与 Java 层 IMS 进行通信的桥梁
2. 创建 Native 层的 InputManager，创建 InputDispatcher、InputReader、EventHub
将 IMS 添加到服务中心
调用 IMS 对象的 start() 函数完成 InputDispatcherThread 、InputReaderThread 的创建和启动
1. InputReader 在其线程循环中不断地从 EventHub 中抽取原始输入事件，进行加工处理后将加工所得的事件放入 InputDispatcher 的派发发队列中
2. InputDispatcher 则在其线程循环中将派发队列中的事件取出，查找合适的窗口，将事件写入到窗口的事件接收管道中
3. 窗口事件接收线程的 Looper 从管道中将事件取出，交由事件处理函数进行事件响应
  暂时无法在飞书文档外展示此内容

源码分析

SystemServer.java {public static void main(String[] args) {new SystemServer().run();}@Overridepublic void run() {startOtherServices(t);}private void startOtherServices(@NonNull TimingsTraceAndSlog t) {InputManagerService inputManager = null;inputManager = new InputManagerService(context);// 将IMS发布给ServiceManager，以便其他人可以访问IMS提供的接口ServiceManager.addService(Context.INPUT_SERVICE,inputManager);// 设置向WMS发起回调的callback对象inputManager.setWindowManagerCallbacks(wm.getInputManagerCallback());// 正式启动IMSinputManager.start();}
}
InputManagerService.java {static class Injector {private final Context mContext;private final Looper mLooper;NativeInputManagerService getNativeService(InputManagerService service) {return new NativeInputManagerService.NativeImpl(service, mContext, mLooper.getQueue());}}InputManagerService(Injector injector) {mHandler = new InputManagerHandler(injector.getLooper());mNative = injector.getNativeService(this);}public void start() {Slog.i(TAG, "Starting input manager");mNative.start();}
}
NativeInputManagerService.java {class NativeImpl implements NativeInputManagerService {/** Pointer to native input manager service object, used by native code. */private final long mPtr;NativeImpl(InputManagerService service, Context context, MessageQueue messageQueue) {mPtr = init(service, context, messageQueue);}private native long init(InputManagerService service, Context context,MessageQueue messageQueue);public native void start();}
}InputManagerService.cpp {static const JNINativeMethod gInputManagerMethods[] = {{"init","(Lcom/android/server/input/InputManagerService;Landroid/content/Context;Landroid/os/MessageQueue;)J",(void*)nativeInit},{"start", "()V", (void*)nativeStart},}static jlong nativeInit(JNIEnv* env, jclass /* clazz */,jobject serviceObj, jobject contextObj, jobject messageQueueObj) {sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);// 新建了一个 NativeInputManager 对象// 此对象将是 Native 层组件与 Java 层 IMS 进行通信的桥梁// 实现了 InputReaderPolicyInterface 与 InputDispatcherPolicyInterface 两个接口NativeInputManager* im = new NativeInputManager(contextObj, serviceObj,messageQueue->getLooper());return reinterpret_cast<jlong>(im);}static void nativeStart(JNIEnv* env, jobject nativeImplObj) {NativeInputManager* im = getNativeInputManager(env, nativeImplObj);status_t result = im->getInputManager()->start();}static NativeInputManager* getNativeInputManager(JNIEnv* env, jobject clazz) {return reinterpret_cast<NativeInputManager*>(env->GetLongField(clazz,gNativeInputManagerServiceImpl.mPtr));}
}
NativeInputManager.cpp {NativeInputManager::NativeInputManager(jobject contextObj,jobject serviceObj, const sp<Looper>& looper) :mLooper(looper), mInteractive(true) {// 创建 Native 层的 InputManagerInputManager* im = new InputManager(this, this);mInputManager = im;defaultServiceManager()->addService(String16("inputflinger"), im);}
}
InputManager.cpp {InputManager::InputManager(const sp<InputReaderPolicyInterface>& readerPolicy,const sp<InputDispatcherPolicyInterface>& dispatcherPolicy) {// 创建 InputDispatchermDispatcher = createInputDispatcher(dispatcherPolicy);//这里的 mBlocker 即封装的 mDispatcher ，mDispatcher 实现了 InputListenerInterface 接口//通过 getListener().notifyMotion(&args) 通知 mDispatcher 处理事件mClassifier = std::make_unique<InputClassifier>(*mDispatcher);mBlocker = std::make_unique<UnwantedInteractionBlocker>(*mClassifier);// 创建 InputReadermReader = createInputReader(readerPolicy, *mBlocker);}status_t InputManager::start() {status_t result = mDispatcher->start();result = mReader->start();return OK;}
}
InputReaderFactory.cpp {std::unique_ptr<InputReaderInterface> createInputReader(const sp<InputReaderPolicyInterface>& policy, InputListenerInterface& listener) {// 这里会创建 EventHub ，并设置事件回调return std::make_unique<InputReader>(std::make_unique<EventHub>(), policy, listener);}
}
InputDispatcherFactory.cpp {std::unique_ptr<InputDispatcherInterface> createInputDispatcher(const sp<InputDispatcherPolicyInterface>& policy) {return std::make_unique<android::inputdispatcher::InputDispatcher>(policy);}
}
InputDispatcher.cpp {status_t InputDispatcher::start() {// 创建供 InputDispatcher 运行的线程 InputDispatcherThreadmThread = std::make_unique<InputThread>("InputDispatcher", [this]() { dispatchOnce(); }, [this]() { mLooper->wake(); });return OK;}
}
InputReader.cpp {status_t InputReader::start() {// 创建供 InputReader 运行的线程 InputReaderThreadmThread = std::make_unique<InputThread>("InputReader", [this]() { loopOnce(); }, [this]() { mEventHub->wake(); });return OK;}
}

事件读取（EventHub）与加工（InputReader）

EventHub

避免不断地轮询这些描述符
不需要为每个描述符创建独立的线程进行阻塞读取，避免了资源浪费的同时又可以获得较快的响应速度。

INotify：Linux 内核所提供的一种文件系统变化通知机制。可以监控文件系统的变化，如文件新建、删除、读写等

inotify_init() 创建一个 inotify 对象，返回一个 notifyFd。
inotify_add_watch 将一个或多个监听添加到 inotify 对象中。
read() 函数从 inotify 对象中读取监听事件

Epoll：监听多个描述符的可读/可写状态。等待返回时携带了可读的描述符

epoll_create(int max_fds) 创建一个 epoll 对象的描述符，之后对 epoll 的操作均使用这个描述符完成。max_fds 参数表示了此 epoll 对象可以监听的描述符的最大数量。
epoll_ctl (int epfd, int op,int fd, struct epoll_event *event) 用于管理注册事件的函数。这个函数可以增加/删除/修改事件的注册。
int epoll_wait(int epfd, structepoll_event * events, int maxevents, int timeout) 用于等待事件的到来。当此函数返回时，events 数组参数中将会包含产生事件的文件描述符。

EventHub.cpp {EventHub::EventHub(void) : mBuiltInKeyboardId(NO_BUILT_IN_KEYBOARD),mNextDeviceId(1),mControllerNumbers(),mNeedToSendFinishedDeviceScan(false),mNeedToReopenDevices(false),mNeedToScanDevices(true),mPendingEventCount(0),mPendingEventIndex(0),mPendingINotify(false) {//使用epoll_create()函数创建一个epoll对象,用来监听设备节点是否有数据可读（有无事件）mEpollFd = epoll_create1(EPOLL_CLOEXEC);//创建一个 inotify 对象 。这个对象将被用来 监听设备节点的增删事件mINotifyFd = inotify_init1(IN_CLOEXEC);std::error_code errorCode;bool isDeviceInotifyAdded = false;if (std::filesystem::exists("/dev/input", errorCode)) {// 将存储设备节点的路径 /dev/input 作为监听对象添加到inotify对象中// 当此文件夹下的设备节点发生创建与删除事件时，都可以通过mINotifyFd读取事件的详细信息mDeviceInputWd = inotify_add_watch(mINotifyFd, "/dev/input", IN_DELETE | IN_CREATE);}struct epoll_event eventItem = {};eventItem.events = EPOLLIN | EPOLLWAKEUP;eventItem.data.fd = mINotifyFd;// 将 mINotifyFd 作为 epoll 的一个监控对象// 当 inotify 事件到来时，epoll_wait() 将立刻返回// EventHub 便可从 mINotifyFd 中读取设备节点的增删信息，并作相应处理int result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mINotifyFd, &eventItem);}
}

InputReader

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源码分析

InputReader.cpp {status_t InputReader::start() {mThread = std::make_unique<InputThread>("InputReader", [this]() { loopOnce(); }, [this]() { mEventHub->wake(); });return OK;}void InputReader::loopOnce() {int32_t oldGeneration;int32_t timeoutMillis;bool inputDevicesChanged = false;std::vector<InputDeviceInfo> inputDevices;// 读取事件，没事件时会 blocksize_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);{ // acquire lockif (count) {processEventsLocked(mEventBuffer, count);}} // release lockmQueuedListener.flush();}void InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {for (const RawEvent* rawEvent = rawEvents; count;) {int32_t type = rawEvent->type;size_t batchSize = 1;if (type < EventHubInterface::FIRST_SYNTHETIC_EVENT) {int32_t deviceId = rawEvent->deviceId;// 处理 输入 事件processEventsForDeviceLocked(deviceId, rawEvent, batchSize);} else {switch (rawEvent->type) {case EventHubInterface::DEVICE_ADDED:// 处理 新增设备 事件addDeviceLocked(rawEvent->when, rawEvent->deviceId);break;case EventHubInterface::DEVICE_REMOVED:// 处理 删除设备 事件removeDeviceLocked(rawEvent->when, rawEvent->deviceId);break;case EventHubInterface::FINISHED_DEVICE_SCAN:// 处理 设备扫描完成 事件handleConfigurationChangedLocked(rawEvent->when);break;default:ALOG_ASSERT(false); // can't happenbreak;}}}}void InputReader::processEventsForDeviceLocked(int32_t eventHubId, const RawEvent* rawEvents,size_t count) {auto deviceIt = mDevices.find(eventHubId);std::shared_ptr<InputDevice>& device = deviceIt->second;device->process(rawEvents, count);}
}
EventHub.cpp {size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSize) {struct input_event readBuffer[bufferSize];RawEvent* event = buffer;Device* device = getDeviceByFdLocked(eventItem.data.fd);while (mPendingEventIndex < mPendingEventCount) {// mPendingEventIndex 指定尚未处理的 epoll_event 的索引const struct epoll_event& eventItem = mPendingEventItems[mPendingEventIndex++];Device* device = getDeviceByFdLocked(eventItem.data.fd);for (;;) {nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);// This must be an input eventif (eventItem.events & EPOLLIN) {// 根据设备id 读取事件到 readBuffer 中int32_t readSize = read(device->fd, readBuffer, sizeof(struct input_event) * capacity);int32_t deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;size_t count = size_t(readSize) / sizeof(struct input_event);for (size_t i = 0; i < count; i++) {struct input_event& iev = readBuffer[i];event->when = processEventTimestamp(iev);event->readTime = systemTime(SYSTEM_TIME_MONOTONIC);event->deviceId = deviceId;event->type = iev.type;event->code = iev.code;event->value = iev.value;event += 1;capacity -= 1;}break;} }// 执行 epoll_wait() 函数等待新的事件到来int pollResult = epoll_wait(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis);}// All done, return the number of events we read.return event - buffer;}
}
InputDevice.cpp {void InputDevice::process(const RawEvent* rawEvents, size_t count) {for (const RawEvent* rawEvent = rawEvents; count != 0; rawEvent++) {for_each_mapper_in_subdevice(rawEvent->deviceId, [rawEvent](InputMapper& mapper) {mapper.process(rawEvent);});--count;}}
}
SingleTouchInputMapper.cpp {void SingleTouchInputMapper::process(const RawEvent* rawEvent) {TouchInputMapper::process(rawEvent);mSingleTouchMotionAccumulator.process(rawEvent);}
}
TouchInputMapper.cpp {void TouchInputMapper::process(const RawEvent* rawEvent) {mCursorButtonAccumulator.process(rawEvent);mCursorScrollAccumulator.process(rawEvent);mTouchButtonAccumulator.process(rawEvent);if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {sync(rawEvent->when, rawEvent->readTime);}}void TouchInputMapper::sync(nsecs_t when, nsecs_t readTime) {// Push a new state.mRawStatesPending.emplace_back();RawState& next = mRawStatesPending.back();next.clear();next.when = when;next.readTime = readTime;// Sync button state.next.buttonState = mTouchButtonAccumulator.getButtonState() | mCursorButtonAccumulator.getButtonState();// Sync scrollnext.rawVScroll = mCursorScrollAccumulator.getRelativeVWheel();mCursorScrollAccumulator.finishSync();processRawTouches(false /*timeout*/);}void TouchInputMapper::processRawTouches(bool timeout) {cookAndDispatch(mCurrentRawState.when, mCurrentRawState.readTime);}void TouchInputMapper::cookAndDispatch(nsecs_t when, nsecs_t readTime) {updateTouchSpots();// 内部处理各个事件，不需要的会进行拦截dispatchButtonRelease(when, readTime, policyFlags);dispatchHoverExit(when, readTime, policyFlags);dispatchTouches(when, readTime, policyFlags);dispatchHoverEnterAndMove(when, readTime, policyFlags);dispatchButtonPress(when, readTime, policyFlags);}void TouchInputMapper::dispatch***(nsecs_t when, nsecs_t readTime, uint32_t policyFlags) {dispatchMotion(...);}void TouchInputMapper::dispatchMotion(nsecs_t when, nsecs_t readTime, uint32_t policyFlags,uint32_t source, int32_t action, int32_t actionButton,int32_t flags, int32_t metaState, int32_t buttonState,int32_t edgeFlags, const PointerProperties* properties,const PointerCoords* coords, const uint32_t* idToIndex,BitSet32 idBits, int32_t changedId, float xPrecision,float yPrecision, nsecs_t downTime) {NotifyMotionArgs args(getContext()->getNextId(), when, readTime, deviceId, source, displayId,policyFlags, action, actionButton, flags, metaState, buttonState,MotionClassification::NONE, edgeFlags, pointerCount, pointerProperties,pointerCoords, xPrecision, yPrecision, xCursorPosition, yCursorPosition,downTime, std::move(frames));// Listener 为 InputDispatcher 实现getListener().notifyMotion(&args);}
}
InputDispatcher.cpp {void InputDispatcher::notifyMotion(const NotifyMotionArgs* args) {bool needWake = false;{// Just enqueue a new motion event.std::unique_ptr<MotionEntry> newEntry = std::make_unique<MotionEntry>(args->id, args->eventTime, args->deviceId,args->source, args->displayId, policyFlags,args->action, args->actionButton, args->flags,args->metaState, args->buttonState,args->classification, args->edgeFlags,args->xPrecision, args->yPrecision,args->xCursorPosition, args->yCursorPosition,args->downTime, args->pointerCount,args->pointerProperties, args->pointerCoords);needWake = enqueueInboundEventLocked(std::move(newEntry));} // release lockif (needWake) {// 唤醒 InputDispatcher 处理接收到的事件mLooper->wake();}}bool InputDispatcher::enqueueInboundEventLocked(std::unique_ptr<EventEntry> newEntry) {bool needWake = mInboundQueue.empty();mInboundQueue.push_back(std::move(newEntry));EventEntry& entry = *(mInboundQueue.back());switch (entry.type) {case EventEntry::Type::KEY: {if (...) {needWake = true;}break;}case EventEntry::Type::MOTION: {if (shouldPruneInboundQueueLocked(static_cast<MotionEntry&>(entry))) {......needWake = true;}break;}}return needWake;}
}

事件的派发

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源码分析

InputDispatcher.cpp {status_t InputDispatcher::start() {mThread = std::make_unique<InputThread>("InputDispatcher", [this]() { dispatchOnce(); }, [this]() { mLooper->wake(); });return OK;}void InputDispatcher::dispatchOnce() {{ // acquire lock// 处理接收的消息dispatchOnceInnerLocked(&nextWakeupTime);// input anr 检测const nsecs_t nextAnrCheck = processAnrsLocked();} // release lock// 开启下次轮训等待 weak 唤醒mLooper->pollOnce(timeoutMillis);}void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) {// 取出从 reader 线程入队的事件mPendingEvent = mInboundQueue.front();mInboundQueue.pop_front();switch (mPendingEvent->type) {case EventEntry::Type::KEY: {std::shared_ptr<KeyEntry> keyEntry = std::static_pointer_cast<KeyEntry>(mPendingEvent);done = dispatchKeyLocked(currentTime, keyEntry, &dropReason, nextWakeupTime);break;}case EventEntry::Type::MOTION: {std::shared_ptr<MotionEntry> motionEntry = std::static_pointer_cast<MotionEntry>(mPendingEvent);done = dispatchMotionLocked(currentTime, motionEntry, &dropReason, nextWakeupTime);break;}}}bool InputDispatcher::dispatchMotionLocked(nsecs_t currentTime, std::shared_ptr<MotionEntry> entry,DropReason* dropReason, nsecs_t* nextWakeupTime) {// Identify targets.std::vector<InputTarget> inputTargets;addGlobalMonitoringTargetsLocked(inputTargets, getTargetDisplayId(*entry));dispatchEventLocked(currentTime, entry, inputTargets);return true;}void InputDispatcher::dispatchEventLocked(nsecs_t currentTime,std::shared_ptr<EventEntry> eventEntry,const std::vector<InputTarget>& inputTargets) {for (const InputTarget& inputTarget : inputTargets) {// Connection 对象中，有两个集合，分别是 outboundQueue 和 waitQueue。// outboundQueue 集合中存放发送给 APP 侧的输入事件// waitQueue 中存放发送给 APP 侧但还没收到回应的输入事件。sp<Connection> connection = getConnectionLocked(inputTarget.inputChannel->getConnectionToken());if (connection != nullptr) {prepareDispatchCycleLocked(currentTime, connection, eventEntry, inputTarget);}}}void InputDispatcher::prepareDispatchCycleLocked(nsecs_t currentTime,const sp<Connection>& connection,std::shared_ptr<EventEntry> eventEntry,const InputTarget& inputTarget) {enqueueDispatchEntriesLocked(currentTime, connection, eventEntry, inputTarget);}void InputDispatcher::enqueueDispatchEntriesLocked(nsecs_t currentTime,const sp<Connection>& connection,std::shared_ptr<EventEntry> eventEntry,const InputTarget& inputTarget) {bool wasEmpty = connection->outboundQueue.empty();// 事件加入到Connection对象中outboundQueue集合enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,InputTarget::FLAG_DISPATCH_AS_***);if (wasEmpty && !connection->outboundQueue.empty()) {startDispatchCycleLocked(currentTime, connection);}}void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,const sp<Connection>& connection) {while (connection->status == Connection::Status::NORMAL && !connection->outboundQueue.empty()) {// 取出队首事件，进行分发DispatchEntry* dispatchEntry = connection->outboundQueue.front();// Publish the event.status_t status;const EventEntry& eventEntry = *(dispatchEntry->eventEntry);switch (eventEntry.type) {case EventEntry::Type::KEY: {const KeyEntry& keyEntry = static_cast<const KeyEntry&>(eventEntry);// Publish the key event.status = connection->inputPublisher.publishKeyEvent(dispatchEntry->seq,dispatchEntry->resolvedEventId, keyEntry.deviceId,keyEntry.source, keyEntry.displayId,std::move(hmac), dispatchEntry->resolvedAction,dispatchEntry->resolvedFlags, keyEntry.keyCode,keyEntry.scanCode, keyEntry.metaState,keyEntry.repeatCount, keyEntry.downTime,keyEntry.eventTime);break;}case EventEntry::Type::MOTION: {const MotionEntry& motionEntry = static_cast<const MotionEntry&>(eventEntry);// Publish the motion event.status = connection->inputPublisher.publishMotionEvent(dispatchEntry->seq,dispatchEntry->resolvedEventId,motionEntry.deviceId, motionEntry.source,motionEntry.displayId, std::move(hmac),dispatchEntry->resolvedAction,motionEntry.actionButton,dispatchEntry->resolvedFlags,motionEntry.edgeFlags, motionEntry.metaState,motionEntry.buttonState,motionEntry.classification,dispatchEntry->transform,motionEntry.xPrecision, motionEntry.yPrecision,motionEntry.xCursorPosition,motionEntry.yCursorPosition,dispatchEntry->rawTransform,motionEntry.downTime, motionEntry.eventTime,motionEntry.pointerCount,motionEntry.pointerProperties, usingCoords);break;}}}
}
InputTransport.cpp {status_t InputPublisher::publishMotionEvent(...) {InputMessage msg;msg.header.type = InputMessage::Type::MOTION;msg.header.seq = seq;msg.body.motion.eventId = eventId;msg.body.motion.deviceId = deviceId;msg.body.motion.source = source;msg.body.motion.displayId = displayId;msg.body.motion.hmac = std::move(hmac);msg.body.motion.action = action;msg.body.motion.actionButton = actionButton;msg.body.motion.flags = flags;msg.body.motion.edgeFlags = edgeFlags;msg.body.motion.metaState = metaState;msg.body.motion.buttonState = buttonState;......return mChannel->sendMessage(&msg);}status_t InputChannel::sendMessage(const InputMessage* msg) {const size_t msgLength = msg->size();InputMessage cleanMsg;msg->getSanitizedCopy(&cleanMsg);ssize_t nWrite;do {// socket 的方式发送到客户端，通过的是 FD 管道nWrite = ::send(getFd(), &cleanMsg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL);} while (nWrite == -1 && errno == EINTR);return OK;}
}

客户端

事件接收初始化

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源码分析

ViewRootImpl.java {public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,int userId) {InputChannel inputChannel = null;if ((mWindowAttributes.inputFeatures & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {inputChannel = new InputChannel();}// 创建 channelres = mWindowSession.addToDisplayAsUser(mWindow, mSeq, mWindowAttributes,getHostVisibility(), mDisplay.getDisplayId(), userId, mTmpFrame,mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,mAttachInfo.mDisplayCutout, inputChannel,mTempInsets, mTempControls);// 通过 loop 监听 channel 的 fdmInputEventReceiver = new WindowInputEventReceiver(inputChannel,Looper.myLooper());}
}
Session.java {public int addToDisplayAsUser(...,InputChannel outInputChannel,...) {return mService.addWindow(this, window, attrs, viewVisibility, displayId, userId,requestedVisibilities, outInputChannel, outInsetsState, outActiveControls,outAttachedFrame, outSizeCompatScale);}
}
WindowManagerService.java {public int addWindow(...,InputChannel outInputChannel,...){final WindowState win = new WindowState(this, session, client, token, parentWindow,appOp[0], seq, attrs, viewVisibility, session.mUid, userId,session.mCanAddInternalSystemWindow);final boolean openInputChannels = (outInputChannel != null && (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0);if  (openInputChannels) {win.openInputChannel(outInputChannel);}}
}
WindowState.java {void openInputChannel(InputChannel outInputChannel) {String name = getName();// 创建两个 channelmInputChannel = mWmService.mInputManager.createInputChannel(name);mInputChannelToken = mInputChannel.getToken();mInputWindowHandle.setToken(mInputChannelToken);mWmService.mInputToWindowMap.put(mInputChannelToken, this);if (outInputChannel != null) {// 将服务端创建的 InputChannel 赋值给 outInputChannelmInputChannel.copyTo(outInputChannel);}}
}
InputManagerService.java {public InputChannel createInputChannel(String name) {return mNative.createInputChannel(name);}
}
com_android_server_input_InputManagerService.cpp {static jobject nativeCreateInputChannel(JNIEnv* env, jobject nativeImplObj, jstring nameObj) {NativeInputManager* im = getNativeInputManager(env, nativeImplObj);// Native 层 InputChannel 的创建base::Result<std::unique_ptr<InputChannel>> inputChannel = im->createInputChannel(name);//Java 层 InputChannel 的创建jobject inputChannelObj = android_view_InputChannel_createJavaObject(env, std::move(*inputChannel));return inputChannelObj;}
}
NativeInputManager.cpp {base::Result<std::unique_ptr<InputChannel>> NativeInputManager::createInputChannel(const std::string& name) {return mInputManager->getDispatcher().createInputChannel(name);}
}InputDispatcher.cpp {Result<std::unique_ptr<InputChannel>> InputDispatcher::createInputChannel(const std::string& name) {std::unique_ptr<InputChannel> serverChannel;std::unique_ptr<InputChannel> clientChannel;// 创建 客户端与服务端的 InputChannel，使用 socket 进行通信status_t result = InputChannel::openInputChannelPair(name, serverChannel, clientChannel);{ // acquire lockconst sp<IBinder>& token = serverChannel->getConnectionToken();// 封装 connection 用于 服务端事件分发sp<Connection> connection = new Connection(std::move(serverChannel), false /*monitor*/, mIdGenerator);mConnectionsByToken.emplace(token, connection);std::function<int(int events)> callback = std::bind(&InputDispatcher::handleReceiveCallback,this, std::placeholders::_1, token);int fd = serverChannel->getFd();// 服务端 接收 客户端发送的事件，代表 客户端 消息处理完成mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, new LooperEventCallback(callback), nullptr);} // release lockreturn clientChannel;}
}
InputTransport.cpp {status_t InputChannel::openInputChannelPair(const std::string& name,std::unique_ptr<InputChannel>& outServerChannel,std::unique_ptr<InputChannel>& outClientChannel) {int sockets[2];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;}
}WindowInputEventReceiver.java {public InputEventReceiver(InputChannel inputChannel, Looper looper) {mInputChannel = inputChannel;mMessageQueue = looper.getQueue();mReceiverPtr = nativeInit(new WeakReference<InputEventReceiver>(this),mInputChannel, mMessageQueue);}
}
android_view_InputEventReceiver.cpp {static jlong nativeInit(JNIEnv* env, jclass clazz, jobject receiverWeak,jobject inputChannelObj, jobject messageQueueObj) {//根据 java 层 InputChannel 找到对应 Native 层 InputChannelstd::shared_ptr<InputChannel> inputChannel =android_view_InputChannel_getInputChannel(env, inputChannelObj);//根据 java 层 MessageQueue 找到对应 Native 层消息队列sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);//创建 Native 层接收器，inputChannel 交给 mInputConsumer(inputChannel)sp<NativeInputEventReceiver> receiver = new NativeInputEventReceiver(env,receiverWeak, inputChannel, messageQueue);status_t status = receiver->initialize();return reinterpret_cast<jlong>(receiver.get());}status_t NativeInputEventReceiver::initialize() {setFdEvents(ALOOPER_EVENT_INPUT);return OK;}void NativeInputEventReceiver::setFdEvents(int events) {if (mFdEvents != events) {mFdEvents = events;int fd = mInputConsumer.getChannel()->getFd();if (events) {//当监听的句柄 fd 发生事件，触发 NativeInputEventReceiver#handleEvent 方法mMessageQueue->getLooper()->addFd(fd, 0, events, this, nullptr);} else {mMessageQueue->getLooper()->removeFd(fd);}}}
}

事件接收

在这里插入图片描述

源码分析

android_view_InputEventReceiver.cpp {//当监听的句柄 fd 发生事件，触发 NativeInputEventReceiver#handleEvent 方法int NativeInputEventReceiver::handleEvent(int receiveFd, int events, void* data) {status_t status = consumeEvents(env, false /*consumeBatches*/, -1, nullptr);}status_t NativeInputEventReceiver::consumeEvents(JNIEnv* env,bool consumeBatches, nsecs_t frameTime, bool* outConsumedBatch) {for (;;) {InputEvent* inputEvent;status_t status = mInputConsumer.consume(&mInputEventFactory,consumeBatches, frameTime, &seq, &inputEvent);jobject inputEventObj;switch (inputEvent->getType()) {case AINPUT_EVENT_TYPE_KEY:inputEventObj = android_view_KeyEvent_fromNative(env,static_cast<KeyEvent*>(inputEvent));break;case AINPUT_EVENT_TYPE_MOTION: {MotionEvent* motionEvent = static_cast<MotionEvent*>(inputEvent);inputEventObj = android_view_MotionEvent_obtainAsCopy(env, motionEvent);break;}}if (inputEventObj) {// receiverWeak 是 ViewRootImpl 中创建的 WindowInputEventReceiver 对象// call WindowInputEventReceiver 的 dispatchInputEvent 方法env->CallVoidMethod(receiverObj.get(),gInputEventReceiverClassInfo.dispatchInputEvent, seq, inputEventObj);}}}
}InputTransport.cpp {status_t InputConsumer::consume(InputEventFactoryInterface* factory, bool consumeBatches,nsecs_t frameTime, uint32_t* outSeq, InputEvent** outEvent) {while (!*outEvent) {// 从 socket 中读取 InputMessagestatus_t result = mChannel->receiveMessage(&mMsg);switch (mMsg.header.type) {case InputMessage::Type::KEY: {KeyEvent* keyEvent = factory->createKeyEvent();// 将 InputMessage 封装成 keyEventinitializeKeyEvent(keyEvent, &mMsg);*outSeq = mMsg.header.seq;*outEvent = keyEvent;break;}case InputMessage::Type::MOTION: {MotionEvent* motionEvent = factory->createMotionEvent();updateTouchState(mMsg);// 将 InputMessage 封装成 MotionEventinitializeMotionEvent(motionEvent, &mMsg);*outSeq = mMsg.header.seq;*outEvent = motionEvent;break;}}return OK;}void InputConsumer::initializeMotionEvent(MotionEvent* event, const InputMessage* msg) {event->initialize(msg->body.motion.eventId, msg->body.motion.deviceId, msg->body.motion.source,msg->body.motion.displayId, msg->body.motion.hmac, msg->body.motion.action,msg->body.motion.actionButton, msg->body.motion.flags,msg->body.motion.edgeFlags, msg->body.motion.metaState,msg->body.motion.buttonState, msg->body.motion.classification, transform,msg->body.motion.xPrecision, msg->body.motion.yPrecision,msg->body.motion.xCursorPosition, msg->body.motion.yCursorPosition,displayTransform, msg->body.motion.downTime, msg->body.motion.eventTime,pointerCount, pointerProperties, pointerCoords);}status_t InputChannel::receiveMessage(InputMessage* msg) {ssize_t nRead;do {// 通过 socket 接收 InputDispatcher 发送的数据nRead = ::recv(getFd(), msg, sizeof(InputMessage), MSG_DONTWAIT);} while (nRead == -1 && errno == EINTR);return OK;}
}

事件分发

在这里插入图片描述

源码分析

ViewRootImpl.java {public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,int userId) {if (inputChannel != null) {mInputEventReceiver = new WindowInputEventReceiver(inputChannel,Looper.myLooper());}}final class WindowInputEventReceiver extends InputEventReceiver {// call by nativeprivate void dispatchInputEvent(int seq, InputEvent event) {onInputEvent(event);}@Overridepublic void onInputEvent(InputEvent event) {enqueueInputEvent(event, this, 0, true);}}void enqueueInputEvent(InputEvent event,InputEventReceiver receiver, int flags, boolean processImmediately) {QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);mPendingInputEventTail = q;doProcessInputEvents();}void doProcessInputEvents() {// Deliver all pending input events in the queue.while (mPendingInputEventHead != null) {QueuedInputEvent q = mPendingInputEventHead;deliverInputEvent(q);}}private void deliverInputEvent(QueuedInputEvent q) {try {InputStage stage;stage.deliver(q);} finally {Trace.traceEnd(Trace.TRACE_TAG_VIEW);}}abstract class InputStage {public final void deliver(QueuedInputEvent q) {result = onProcess(q);}}final class ViewPostImeInputStage extends InputStage {protected int onProcess(QueuedInputEvent q) {if (q.mEvent instanceof KeyEvent) {return processKeyEvent(q);} else {return processPointerEvent(q);}}private int processPointerEvent(QueuedInputEvent q) {final MotionEvent event = (MotionEvent)q.mEvent;boolean handled = mView.dispatchPointerEvent(event);return handled ? FINISH_HANDLED : FORWARD;}}
}
View.java {public final boolean dispatchPointerEvent(MotionEvent event) {if (event.isTouchEvent()) {return dispatchTouchEvent(event);} else {return dispatchGenericMotionEvent(event);}}
}
DecorView.java {public boolean dispatchTouchEvent(MotionEvent event) {//Activity 实现了 Window.Callback 这个接口final Window.Callback cb = mWindow.getCallback();return cb != null && !mWindow.isDestroyed() && mFeatureId < 0? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev);}
}
Activity.java {public boolean dispatchTouchEvent(MotionEvent ev) {if (ev.getAction() == MotionEvent.ACTION_DOWN) {onUserInteraction();}if (getWindow().superDispatchTouchEvent(ev)) {return true;}return onTouchEvent(ev);}
}
PhoneWindow.java {public boolean superDispatchTouchEvent(MotionEvent event) {return mDecor.superDispatchTouchEvent(event);}
}
DecorView.java {public boolean superDispatchTouchEvent(MotionEvent event) {return super.dispatchTouchEvent(event);}
}
ViewGroup.java {public boolean dispatchTouchEvent(MotionEvent ev) {onInterceptTouchEvent(ev);for (int i = childrenCount - 1; i >= 0; i--) {dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)}}private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,View child, int desiredPointerIdBits) {return child.dispatchTouchEvent(event);}
}
View.java{public boolean dispatchTouchEvent(MotionEvent event) {onTouchEvent(event)}public boolean onTouchEvent(MotionEvent event) {//do sameing}
}

key	描述
EV_KEY	键盘、按钮或其他类似按键的状态变化
EV_REL	相对坐标轴值的变化，例如鼠标移动5个单位
EV_ABS	绝对轴值的变化，例如触摸屏上触摸的坐标
SYN_REPORT	将事件同步并打包

Android 输入系统

概述

概念解释

Input 系统流程

服务端

Input 系统初始化 IMS

源码分析

事件读取（EventHub）与加工（InputReader）

EventHub

InputReader

源码分析

事件的派发

源码分析

客户端

事件接收初始化

源码分析

事件接收

源码分析

事件分发

源码分析

相关工具

getevent

sendevent

dumpsys input

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