--- theme: juejin highlight: androidstudio --- > 接某某公司的电话面试，聊着聊着对方来了句： > 你知道事件是怎么传递到Activity的吗？ > ps: 我在电话那头懵了🙈，一时语塞，难道是要造火箭？ > **基于android11源码进行分析** 回到正题，不管造不造火箭，我们来看一下这个问题我们在 `Activity` 内复写的 `dispatchTouchEvent` 方法中使用: `Thread.dumpStack()` 打印当前线程的堆栈信息： ```kotlin java.lang.Exception: Stack trace at java.lang.Thread.dumpStack(Thread.java:1523) at com.melody.demo.MainActivity.dispatchTouchEvent(MainActivity.kt:31) at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69) at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:679) at android.view.View.dispatchPointerEvent(View.java:13961) at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6402) at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:6197) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5586) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5639) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5605) at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:5763) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5613) at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5820) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5586) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5639) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5605) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5613) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5586) at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8680) at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8600) at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:8553) at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8938) at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:239) at android.os.MessageQueue.nativePollOnce(Native Method) at android.os.MessageQueue.next(MessageQueue.java:363) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:8668) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1109) ``` 我们参考上面的堆栈信息，来看一下里面的源码： `注意：不要看行数，我们需要前后源码连起来看` ### 1.ZygoteInit.main函数 `main函数` 为开篇入口： ```kotlin //com.android.internal.os.ZygoteInit public static void main(String argv[]) { //统一用省略号代替部分代码... ... try { .... if (startSystemServer) { //fork出子进程SystemServer Runnable r = forkSystemServer(abiList, zygoteSocketName, zygoteServer); if (r != null) { r.run(); return; } } //caller.run()执行内部方法 //循环读取消息，获取子进程发送的消息 caller = zygoteServer.runSelectLoop(abiList); } catch (Throwable ex) { throw ex; } finally { ... } if (caller != null) { caller.run(); } } ``` 我们根据：`RuntimeInit$MethodAndArgsCaller.run` 反向推导出来源是来自`forkSystemServer`，继续看： ```kotlin //com.android.internal.os.ZygoteInit private static Runnable forkSystemServer(String abiList, String socketName, ZygoteServer zygoteServer) { .... //使用硬编码的方式定义出启动system server的参数字符串args String args[] = ... ZygoteArguments parsedArgs = null; try { //zygote命令行参数，把args解析为需要的参数 parsedArgs = new ZygoteArguments(args); ... //fork创建SystemServer pid = Zygote.forkSystemServer(....); } catch (IllegalArgumentException ex) { throw new RuntimeException(ex); } if (pid == 0) {//表示子进程执行 .... return handleSystemServerProcess(parsedArgs); } return null; } ``` 接着奏乐接着舞，我们看下`handleSystemServerProcess`做了什么？ ```kotlin //com.android.internal.os.ZygoteInit private static Runnable handleSystemServerProcess(ZygoteArguments parsedArgs) { .... if (parsedArgs.mInvokeWith != null) { String[] args = parsedArgs.mRemainingArgs; ..... //启动应用进程 WrapperInit.execApplication(parsedArgs.mInvokeWith, parsedArgs.mNiceName, parsedArgs.mTargetSdkVersion, VMRuntime.getCurrentInstructionSet(), null, args); } else { ClassLoader cl = null; if (systemServerClasspath != null) { //创建类加载器 cl = createPathClassLoader(systemServerClasspath, parsedArgs.mTargetSdkVersion); //赋予当前线程 Thread.currentThread().setContextClassLoader(cl); } return ZygoteInit.zygoteInit(parsedArgs.mTargetSdkVersion, parsedArgs.mDisabledCompatChanges, parsedArgs.mRemainingArgs, cl); } } ``` 我们看看 `zygoteInit`里面做了什么事情： ```java //com.android.internal.os.ZygoteInit public static final Runnable zygoteInit(int targetSdkVersion, long[] disabledCompatChanges, String[] argv, ClassLoader classLoader) { .... //将System.out和System.err重定向到安卓日志。 RuntimeInit.redirectLogStreams(); //通用初始化：异常捕获、重置log配置、网络流量统计等 RuntimeInit.commonInit(); //不懂，哈哈哈 ZygoteInit.nativeZygoteInit(); //最终会进入ActivityThread 的 main 方法 return RuntimeInit.applicationInit(targetSdkVersion, disabledCompatChanges, argv, classLoader); } ``` ### 2.ActivityThread的main函数走起，看看`applicationInit`，又有什么小九九： ```java protected static Runnable applicationInit(int targetSdkVersion, long[] disabledCompatChanges, String[] argv, ClassLoader classLoader) { .... return findStaticMain(args.startClass, args.startArgs, classLoader); } ``` 看好了，小兄弟 `findStaticMain：` ```java //com.android.internal.os.RuntimeInit protected static Runnable findStaticMain(String className, String[] argv, ClassLoader classLoader) { Class cl; try { //通过 className("android.app.ActivityThread" )反射得到 ActivityThread 类 //className 通过 AMS 等其它地方传递过来的，并不是唯一 cl = Class.forName(className, true, classLoader); } catch (ClassNotFoundException ex) { throw new RuntimeException(....); } Method m; try { //拿到 ActivityThread的 main 函数 m = cl.getMethod("main", new Class[] { String[].class }); } catch (NoSuchMethodException ex) { throw new RuntimeException(...); } catch (SecurityException ex) { throw new RuntimeException(...); } int modifiers = m.getModifiers(); if (! (Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers))) { throw new RuntimeException(...); } return new MethodAndArgsCaller(m, argv); } static class MethodAndArgsCaller implements Runnable { public MethodAndArgsCaller(Method method, String[] args) { mMethod = method; mArgs = args; } public void run() { try { //开始执行 ActivityThread的main 方法 mMethod.invoke(null, new Object[] { mArgs }); } catch (IllegalAccessException ex) { throw new RuntimeException(ex); } catch (InvocationTargetException ex) { Throwable cause = ex.getCause(); if (cause instanceof RuntimeException) { throw (RuntimeException) cause; } else if (cause instanceof Error) { throw (Error) cause; } throw new RuntimeException(ex); } } } ``` 到此，我们才发现，刚刚执行到 `RuntimeInit$MethodAndArgsCaller.run`，里面将会通过`invoke`执行 `ActivityThread.main(args)` ### 3.InputEventReceiver.dispatchInputEvent 我们在文章一开始打印的堆栈信息的时候，能看到执行的顺序是： ```java Looper.loop() -> Message.getNext() -> nativePollOnce(ptr,nextPollTimeoutMillis) -> InputEventReceiver.dispatchInputEvent ``` #### 3.1 Looper.nativePollOnce [**点击查看 android_os_MessageQueue.cpp 源码**](https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-11.0.0_r40/core/jni/android_os_MessageQueue.cpp) ```c++ //frameworks/base/core/jni/android_os_MessageQueue.cpp //部分实现 static void android_os_MessageQueue_nativePollOnce(JNIEnv* env, jobject obj, jlong ptr, jint timeoutMillis) { NativeMessageQueue* nativeMessageQueue = reinterpret_cast(ptr); nativeMessageQueue->pollOnce(env, obj, timeoutMillis); } ``` `Java`层的`MessageQueue`对应`Native`层的`NativeMessageQueue` ```c++ void NativeMessageQueue::pollOnce(JNIEnv* env, jobject pollObj, int timeoutMillis) { mPollEnv = env; mPollObj = pollObj; //调用了Native Looper的pollOnce() mLooper->pollOnce(timeoutMillis); mPollObj = NULL; mPollEnv = NULL; ... } ``` [**点击查看 Looper.cpp源码**](https://android.googlesource.com/platform/system/core/+/refs/tags/android-11.0.0_r40/libutils/Looper.cpp) ```c++ //system/core/libutils/Looper.cpp int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData) { int result = 0; for (;;) { ... result = pollInner(timeoutMillis); } } //喜欢看更多细节的，可以点击上面的链接自己查看源码 int Looper::pollInner(int timeoutMillis) { struct epoll_event eventItems[EPOLL_MAX_EVENTS]; // 阻塞等待epoll返回事件,然后再处理Message和fd event int eventCount = epoll_wait(mEpollFd.get(), eventItems, EPOLL_MAX_EVENTS, timeoutMillis); ... for (int i = 0; i < eventCount; i++) { //处理每一个读取到的event int fd = eventItems[i].data.fd; uint32_t epollEvents = eventItems[i].events; ... ssize_t requestIndex = mRequests.indexOfKey(fd); ... //处理request，生成对应的reponse对象，push到mResponses数组 pushResponse(events, mRequests.valueAt(requestIndex)); } Done: ; .... // Invoke all response callbacks. for (size_t i = 0; i < mResponses.size(); i++) { Response& response = mResponses.editItemAt(i); if (response.request.ident == POLL_CALLBACK) { int fd = response.request.fd; int events = response.events; void* data = response.request.data; //大家注意了，注意此处的handleEvent,往下翻有解释 int callbackResult = response.request.callback->handleEvent(fd, events, data); ... result = POLL_CALLBACK; } } return result; } // Looper在阻塞的时候，可以通过wake()方法来唤醒它， // 通过往mWakeEventFd写入"1"，会导致epoll_wait返回，从而取消轮询状态。 void Looper::wake() { uint64_t inc = 1; /* * 向mWakeEventFd写入数据，用于唤醒消息队列 * 调用这个方法后, epoll_wait函数会返回，沿着调用链一路向上 * pollInner->pollOnce->pollOnce->android_os_MessageQueue_nativePollOnce->nativePollOnce->next * 此时Looper.loop()调用的next()会返回，循环体继续执行 */ ssize_t nWrite = TEMP_FAILURE_RETRY(write(mWakeEventFd.get(), &inc, sizeof(uint64_t))); } ``` #### 3.2 callback->handleEvent 看一下`response.request.callback->handleEvent(fd, events, data)` ```c++ //system/core/libutils/Looper.cpp SimpleLooperCallback::SimpleLooperCallback(Looper_callbackFunc callback) : mCallback(callback) { } 👆👆👆👆 int SimpleLooperCallback::handleEvent(int fd, int events, void* data) { return mCallback(fd, events, data); } ``` 源码到此处的话，就感觉断了一样， **那么到底怎么触发InputEventReceiver.dispatchInputEvent的呢？** 我们只能从InputEvent下手了，我们知道Android中有个叫 InputManagerService的类，怎么创建出来的？大家可以去看一下**SystemServer.java** 代码 #### 3.3 SystemServer ```java //com.android.server.SystemServer public final class SystemServer{ public static void main(String[] args) { new SystemServer().run(); } private void run() { .... //创建InputManagerService //交给ServiceManager管理 //绑定WMS的InputManagerCallback //执行inputMagerService.start() startOtherServices(t); } } ``` #### 3.4 new InputManagerService 构造函数内会调用：**nativeInit()**, 初始化Native层的InputManagerService： [**点击查看 InputManagerService.cpp 源码**](https://android.googlesource.com/platform/frameworks/base/+/master/services/core/jni/com_android_server_input_InputManagerService.cpp) ```c++ //frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp static jlong nativeInit(JNIEnv* env, jclass /* clazz */, jobject serviceObj, jobject contextObj, jobject messageQueueObj) { ... //NativeInputManager 内部创建了【InputManager】,感兴趣的自行查看源码学习 NativeInputManager* im = new NativeInputManager(contextObj, serviceObj, messageQueue->getLooper()); im->incStrong(0); return reinterpret_cast(im); } ``` 接着看**InputManager**里面初始了什么? [**点击查看 InputManager 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/services/inputflinger/InputManager.cpp) ```c++ //platform/frameworks/native/services/inputflinger/InputManager.cpp InputManager::InputManager( const sp& readerPolicy, const sp& dispatcherPolicy) { //初始化InputDispatcher mDispatcher = createInputDispatcher(dispatcherPolicy); //初始化InputReader mReader = createInputReader(readerPolicy, mClassifier); } ``` SystemServer的**main函数**里面执行了 **InputManagerService.start()** ```c++ //platform/frameworks/native/services/inputflinger/InputManager.cpp status_t InputManager::start() { //InputDispatcher.start() status_t result = mDispatcher->start(); if (result) { return result; } //InputReader.start() result = mReader->start(); if (result) { //InputDispatcher.stop() mDispatcher->stop(); return result; } return OK; } ``` [**点击查看 InputDispatcher.cpp 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/services/inputflinger/dispatcher/InputDispatcher.cpp) ```c++ //frameworks/native/services/inputflinger/InputDispatcher.cpp status_t InputDispatcher::start() { if (mThread) { return ALREADY_EXISTS; } mThread = std::make_unique( "InputDispatcher", [this]() { dispatchOnce(); }, [this]() { mLooper->wake(); }); return OK; } ``` [**点击查看 InputReader.cpp 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/services/inputflinger/reader/InputReader.cpp) ```c++ //platform/frameworks/native/services/inputflinger/reader/InputReader.cpp status_t InputReader::start() { if (mThread) { return ALREADY_EXISTS; } mThread = std::make_unique( "InputReader", [this]() { loopOnce(); }, [this]() { mEventHub->wake(); }); return OK; } ``` 代码看到这里，并不清楚后面会往哪走，发现一个新的玩意[**点击查看 EventHub.cpp 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/services/inputflinger/reader/EventHub.cpp) 好家伙，感觉做系统层开发的太苦逼了，好多东西🤔

```c++ //platform/frameworks/native/services/inputflinger/reader/EventHub.cpp void EventHub::wake() { ssize_t nWrite; do { //EventHub::getEvents方法中有这么一段代码： //int pollResult = epoll_wait(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis) //wake的时候往pipe的写端mWakeWritePipeFd写一字符"W" //唤醒epoll_wait nWrite = write(mWakeWritePipeFd, "W", 1); } while (nWrite == -1 && errno == EINTR); ... } ``` 回到上面的`loopOnce()`，执行了这个方法，才会执行`EventHub::wake()` ```c++ //platform/frameworks/native/services/inputflinger/reader/InputReader.cpp void InputReader::loopOnce() { ... size_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE); { mReaderIsAliveCondition.broadcast(); if (count) { //处理事件 processEventsLocked(mEventBuffer, count); } ... } ... mQueuedListener->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) { ... //数据事件的处理 processEventsForDeviceLocked(deviceId, rawEvent, batchSize); } else { .... } ... } } void InputReader::processEventsForDeviceLocked(int32_t eventHubId, const RawEvent* rawEvents,size_t count) { ... std::shared_ptr& device = deviceIt->second; device->process(rawEvents, count); } ``` [**点击查看 InputDevice.cpp 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/services/inputflinger/reader/InputDevice.cpp) ```c++ //platform/hardware/libhardware/modules/input/evdev/InputDevice.cpp void InputDevice::process(const RawEvent* rawEvents, size_t count) { for (const RawEvent* rawEvent = rawEvents; count != 0; rawEvent++) { ... if (rawEvent->type == EV_SYN && rawEvent->code == SYN_DROPPED) { mDropUntilNextSync = true; reset(rawEvent->when); } else { for_each_mapper_in_subdevice(rawEvent->deviceId, [rawEvent](InputMapper& mapper) { //调用具体InputMapper来处理 mapper.process(rawEvent); }); } --count; } } ``` mapper.process(event) 直接贴后面执行的一些方法 `依次执行的顺序：` [**点击查看 TouchInputMapper.cpp 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/services/inputflinger/reader/mapper/TouchInputMapper.cpp) ```java //platform/frameworks/native/services/inputflinger/reader/mapper/TouchInputMapper.cpp void TouchInputMapper::process(const RawEvent* rawEvent) void TouchInputMapper::sync(nsecs_t when) void TouchInputMapper::processRawTouches(bool timeout) void TouchInputMapper::cookAndDispatch(nsecs_t when) void TouchInputMapper::dispatchTouches(nsecs_t when, uint32_t policyFlags) void TouchInputMapper::dispatchMotion(nsecs_t when, uint32_t policyFlags, uint32_t source, int32_t action, int32_t actionButton, int32_t flags,...) ``` `TouchInputMapper::dispatchMotion`方法最后会调用： ```c++ void TouchInputMapper::dispatchMotion(...){ ... getListener()->notifyMotion(&args); } getListener()实际上是InputDispatcher void InputDispatcher::notifyMotion(const NotifyMotionArgs* args) ``` 好家伙，再回来看看`InputDispatcher`，话说上面我们没有分析 `InputDispatcher.start()`内部的`dispatchOnce()`，细节方面感兴趣的可以自己去看源码，我们提供一下`内部方法调用`的顺序： ```c++ //frameworks/native/services/inputflinger/InputDispatcher.cpp void InputDispatcher::dispatchOnce() void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) bool InputDispatcher::dispatchMotionLocked(nsecs_t currentTime, MotionEntry* entry,DropReason* dropReason, nsecs_t* nextWakeupTime) void InputDispatcher::dispatchEventLocked(nsecs_t currentTime, EventEntry* eventEntry,const std::vector& inputTargets) void InputDispatcher::prepareDispatchCycleLocked(nsecs_t currentTime,const sp& connection,EventEntry* eventEntry,const InputTarget& inputTarget) void InputDispatcher::enqueueDispatchEntriesLocked(nsecs_t currentTime,const sp& connection,EventEntry* eventEntry,const InputTarget& inputTarget) void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,const sp& connection) ``` 我们看最后一个方法`startDispatchCycleLocked`： ```c++ //frameworks/native/services/inputflinger/InputDispatcher.cpp void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,const sp& connection) { .... case EventEntry::Type::MOTION: { .... // Publish the motion event. status = connection->inputPublisher.publishMotionEvent(..) .... } } ``` `InputPublisher`在哪儿呢？谷歌了下，发现在这里 [**点击查看 InputTransport.cpp 源码**](https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-11.0.0_r40/libs/input/InputTransport.cpp) ```c++ //frameworks/native/libs/input/InputTransport.cpp status_t InputPublisher::publishMotionEvent(....) { .... InputMessage msg; msg.header.type = InputMessage::Type::MOTION; .... msg.body.motion.downTime = downTime; msg.body.motion.eventTime = eventTime; msg.body.motion.pointerCount = pointerCount; .... //进行跨进程通信 return mChannel->sendMessage(&msg); } ``` 不抛弃，不放弃，离真相越近，😂越心疼做framework开发的程序员👨‍💻‍ ```c++ //frameworks/native/libs/input/InputTransport.cpp //发送消息 status_t InputChannel::sendMessage(const InputMessage* msg) { const size_t msgLength = msg->size(); InputMessage cleanMsg; msg->getSanitizedCopy(&cleanMsg); ssize_t nWrite; do { //写入Fd nWrite = ::send(mFd.get(), &cleanMsg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL); } while (nWrite == -1 && errno == EINTR); ... return OK; } //接收消息 status_t InputChannel::receiveMessage(InputMessage* msg) { ssize_t nRead; do { nRead = ::recv(mFd.get(), msg, sizeof(InputMessage), MSG_DONTWAIT); } while (nRead == -1 && errno == EINTR); ... return OK; } ``` #### 3.5 InputChannel在哪里创建的？不知道有多少人能看到此处，我们在文章开始那里提示大家： `注意：不要看行数，我们需要前后源码连起来看` 我们看这一行：`ViewRootImpl$WindowInputEventReceiver.onInputEvent()`，进入**ViewRootImpl**发现：**setView(...)** 方法内部初始化了**InputChannel** ```java //android.view.ViewRootImpl 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(); } .... //WindowInputEventReceiver继承自InputEventReceiver //对InputChannel中输入事件的监听 mInputEventReceiver = new WindowInputEventReceiver(inputChannel, Looper.myLooper()); .... } ``` `WindowInputEventReceiver`初始化后，构造函数里面会执行`nativeInit(..)` #### 3.6 如何触发dispatchInputEvent? [**点击查看 InputEventReceiver.cpp 源码**](https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-11.0.0_r40/core/jni/android_view_InputEventReceiver.cpp) ```c++ //platform/frameworks/base/core/jni/android_view_InputEventReceiver.cpp static jlong nativeInit(JNIEnv* env, jclass clazz, jobject receiverWeak, jobject inputChannelObj, jobject messageQueueObj) { ... sp receiver = new NativeInputEventReceiver(env, receiverWeak, inputChannel, messageQueue); status_t status = receiver->initialize(); ... receiver->incStrong(gInputEventReceiverClassInfo.clazz); // retain a reference for the object return reinterpret_cast(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) { //大家可以查看上面我们提供的👆👆Looper.cpp源码地址👆👆，进去看一下addFd方法 //调用Looper.addFd()完成的赋值操作 //Looper.cpp里面的 mCallback =『此处的this』 //所以：Looper.cpp里面的handleEvent = NativeInputEventReceiver::handleEvent(...) //看文章上面的Looper::pollInner方法 mMessageQueue->getLooper()->addFd(fd, 0, events, this, nullptr); } else { mMessageQueue->getLooper()->removeFd(fd); } } } ``` 看一下 `NativeInputEventReceiver::handleEvent(..)` ```c++ //platform/frameworks/base/core/jni/android_view_InputEventReceiver.cpp int NativeInputEventReceiver::handleEvent(int receiveFd, int events, void* data) { .... if (events & ALOOPER_EVENT_INPUT) { JNIEnv* env = AndroidRuntime::getJNIEnv(); //处理事件 status_t status = consumeEvents(env, false /*consumeBatches*/, -1, nullptr); mMessageQueue->raiseAndClearException(env, "handleReceiveCallback"); return status == OK || status == NO_MEMORY ? 1 : 0; } ... return 1; } status_t NativeInputEventReceiver::consumeEvents(JNIEnv* env, bool consumeBatches, nsecs_t frameTime, bool* outConsumedBatch) { ..... ScopedLocalRef receiverObj(env, nullptr); bool skipCallbacks = false; for (;;) { uint32_t seq; InputEvent* inputEvent; status_t status = mInputConsumer.consume(&mInputEventFactory, consumeBatches, frameTime, &seq, &inputEvent); .... if (!skipCallbacks) { .... jobject inputEventObj; switch (inputEvent->getType()) { .... if (inputEventObj) { //执行Java类里面的 InputEventReceiver.dispachInputEvent() env->CallVoidMethod(receiverObj.get(), gInputEventReceiverClassInfo.dispatchInputEvent, seq, inputEventObj); if (env->ExceptionCheck()) { skipCallbacks = true; } env->DeleteLocalRef(inputEventObj); } ... } ... } } ``` 执行👇👇下面这行代码，会执行到 `InputEventReceiver.dispachInputEvent()` ```c++ //😩不容易，终于可以跳出来了 CallVoidMethod(receiverObj.get(), gInputEventReceiverClassInfo.dispatchInputEvent, seq, inputEventObj) ``` ### 4.enqueueInputEvent 上面触发了dispatchInputEvent之后，回调onInputEvent ```java //android.view.ViewRootImpl.WindowInputEventReceiver final class WindowInputEventReceiver extends InputEventReceiver { public void onInputEvent(InputEvent event) { ... enqueueInputEvent(...) ... } } ``` ### 5.doProcessInputEvents ```java //android.view.ViewRootImpl void enqueueInputEvent(InputEvent event, InputEventReceiver receiver, int flags, boolean processImmediately) { .... //最终还是会执行doProcessInputEvents() if (processImmediately) { //立即执行 doProcessInputEvents(); } else { //延迟执行，最终还是会执行doProcessInputEvents() scheduleProcessInputEvents(); } } ``` ### 6.doProcessInputEvents ```java //android.view.ViewRootImpl void doProcessInputEvents() { // 传递队列中所有待处理的事件 while (mPendingInputEventHead != null) { QueuedInputEvent q = mPendingInputEventHead; mPendingInputEventHead = q.mNext; if (mPendingInputEventHead == null) { mPendingInputEventTail = null; } q.mNext = null; mPendingInputEventCount -= 1; .... deliverInputEvent(q); } ... } ``` ### 7.deliverInputEvent ```java //android.view.ViewRootImpl private void deliverInputEvent(QueuedInputEvent q) { ... InputStage stage; if (q.shouldSendToSynthesizer()) { stage = mSyntheticInputStage; } else { stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage; } .... if (stage != null) { handleWindowFocusChanged(); //使用责任链模式，开始传递，最终会执行到ViewPostImeInputStage.onProcess stage.deliver(q); } else { finishInputEvent(q); } ... } ``` ### 8.ViewPostImeInputStage.onProcess ```java //android.view.ViewRootImpl.ViewPostImeInputStage final class ViewPostImeInputStage extends InputStage { @Override protected int onProcess(QueuedInputEvent q) { ... final int source = q.mEvent.getSource(); if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) { //传递到view中 return processPointerEvent(q); } ... } } ``` ### 9.ViewPostImeInputStage.processPointerEvent ```java private int processPointerEvent(QueuedInputEvent q) { final MotionEvent event = (MotionEvent)q.mEvent; ... //执行view的dispatchPointerEvent,返回事件是否由此view处理 boolean handled = mView.dispatchPointerEvent(event); maybeUpdatePointerIcon(event); maybeUpdateTooltip(event); mAttachInfo.mHandlingPointerEvent = false; .... return handled ? FINISH_HANDLED : FORWARD; } ``` ### 10.View.dispatchPointerEvent ```java //android.view.View public final boolean dispatchPointerEvent(MotionEvent event) { if (event.isTouchEvent()) {//如果是触摸事件则100%是true return dispatchTouchEvent(event); } else { return dispatchGenericMotionEvent(event); } } ``` ### 11.DecorView.dispatchTouchEvent 我们进入ViewRootImpl里面再瞅一眼，上面刚刚分析的`View.dispatchPointerEvent`，这个View如果是ViewGroup，那么它就是`DecorView` ```java //com.android.internal.policy.DecorView @Override public boolean dispatchTouchEvent(MotionEvent ev) { //这个mWindow是PhoneWindow final Window.Callback cb = mWindow.getCallback(); //调用：WindowCallbackWrapper.dispatchTouchEvent return cb != null && !mWindow.isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev); } ``` #### 11.1 PhoneWindow怎么来的？打开Activity的源码，能看到`Activity.attatch`方法内部初始化了PhoneWindow ```java //android.app.Activity final void attach(Context context, ActivityThread aThread,...) { attachBaseContext(context); mFragments.attachHost(null /*parent*/); //初始化PhoneWindow mWindow = new PhoneWindow(this, window, activityConfigCallback); mWindow.setWindowControllerCallback(mWindowControllerCallback); //设置Callback mWindow.setCallback(this); mWindow.setOnWindowDismissedCallback(this); mWindow.getLayoutInflater().setPrivateFactory(this); ... mWindowManager = mWindow.getWindowManager(); ... } ``` #### 11.2 DecorView怎么和window关联到一起的？打开`PhoneWindow`，查看里面的`setContentView`方法，内部调用了`installDecor()` ```java //com.android.internal.policy.PhoneWindow private void installDecor() { ... //这样就关联起来了 mDecor.setWindow(this); .... } ``` ### 12.WindowCallbackWrapper.dispatchTouchEvent ```java //curtains.internal.WindowCallbackWrapper override fun dispatchTouchEvent(event: MotionEvent?): Boolean { return if (event != null) { val iterator = listeners.touchEventInterceptors.iterator() val dispatch: (MotionEvent) -> DispatchState = object : (MotionEvent) -> DispatchState { override fun invoke(interceptedEvent: MotionEvent): DispatchState { return if (iterator.hasNext()) { val nextInterceptor = iterator.next() nextInterceptor.intercept(interceptedEvent, this) } else { DispatchState.from(delegate.dispatchTouchEvent(interceptedEvent)) } } } //如果设置了OnTouchEventListener,那么就会执行这个iterator if (iterator.hasNext()) { val firstInterceptor = iterator.next() firstInterceptor.intercept(event, dispatch) } else { //没有设置OnTouchEventListener的场景 //delegate = Activity DispatchState.from(delegate.dispatchTouchEvent(event)) } is Consumed } else { //delegate = Activity delegate.dispatchTouchEvent(event) } } ``` 最终执行到 `Activity.dispatchTouchEvent`，分析结束，终于传递到Activity了。