点击手机屏幕，可以分发input 事件到对应的view，由上一节知道input 是运行在system 进程的，那应用进程与系统进程是如何通讯的呢，相信本文可以给到一点小小的答案。
先给个结论：应用在resume 的时候才去建立与input 服务的联系。其中还创建了Token 对象和WindowState 对象等
/frameworks/base/core/java/android/app/ActivityThread.java
应用执行resume 代码流程
4826 @Override
4827 public void handleResumeActivity(ActivityClientRecord r, boolean finalStateRequest,
4828 boolean isForward, String reason) {
4829 // If we are getting ready to gc after going to the background, well
4830 // we are back active so skip it.
4831 unscheduleGcIdler();
4832 mSomeActivitiesChanged = true;
4833
4834 // TODO Push resumeArgs into the activity for consideration
4835 // skip below steps for double-resume and r.mFinish = true case.
// 这里去回调应用的onsesume 方法
4836 if (!performResumeActivity(r, finalStateRequest, reason)) {
4837 return;
4838 }
4839 if (mActivitiesToBeDestroyed.containsKey(r.token)) {
4840 // Although the activity is resumed, it is going to be destroyed. So the following
4841 // UI operations are unnecessary and also prevents exception because its token may
4842 // be gone that window manager cannot recognize it. All necessary cleanup actions
4843 // performed below will be done while handling destruction.
4844 return;
4845 }
4846
4847 final Activity a = r.activity;
4848
4849 if (localLOGV) {
4850 Slog.v(TAG, "Resume " + r + " started activity: " + a.mStartedActivity
4851 + ", hideForNow: " + r.hideForNow + ", finished: " + a.mFinished);
4852 }
4853
4854 final int forwardBit = isForward
4855 ? WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;
4856
4857 // If the window hasn't yet been added to the window manager,
4858 // and this guy didn't finish itself or start another activity,
4859 // then go ahead and add the window.
4860 boolean willBeVisible = !a.mStartedActivity;
4861 if (!willBeVisible) {
4862 willBeVisible = ActivityClient.getInstance().willActivityBeVisible(
4863 a.getActivityToken());
4864 }
4865 if (r.window == null && !a.mFinished && willBeVisible) {
4866 r.window = r.activity.getWindow();
4867 View decor = r.window.getDecorView();
4868 decor.setVisibility(View.INVISIBLE);
4869 ViewManager wm = a.getWindowManager();
4870 WindowManager.LayoutParams l = r.window.getAttributes();
4871 a.mDecor = decor;
4872 l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
4873 l.softInputMode |= forwardBit;
4874 if (r.mPreserveWindow) {
4875 a.mWindowAdded = true;
4876 r.mPreserveWindow = false;
4877 // Normally the ViewRoot sets up callbacks with the Activity
4878 // in addView->ViewRootImpl#setView. If we are instead reusing
4879 // the decor view we have to notify the view root that the
4880 // callbacks may have changed.
4881 ViewRootImpl impl = decor.getViewRootImpl();
4882 if (impl != null) {
4883 impl.notifyChildRebuilt();
4884 }
4885 }
4886 if (a.mVisibleFromClient) {
4887 if (!a.mWindowAdded) {
4888 a.mWindowAdded = true;
// 这里去增加view，并设置了 mWindowAdded 为true 的。保证只增加一次
4889 wm.addView(decor, l);/frameworks/base/core/java/android/view/WindowManagerImpl.java
// addview 方法
145 @Override
146 public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
147 applyTokens(params);
148 mGlobal.addView(view, params, mContext.getDisplayNoVerify(), mParentWindow,
149 mContext.getUserId());
150 }/frameworks/base/core/java/android/view/WindowManagerGlobal.java
// addview 方法
145 @Override
146 public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
147 applyTokens(params);
148 mGlobal.addView(view, params, mContext.getDisplayNoVerify(), mParentWindow,
149 mContext.getUserId());
150 }
/frameworks/base/core/java/android/view/WindowManagerGlobal.java
304 public void addView(View view, ViewGroup.LayoutParams params,
305 Display display, Window parentWindow, int userId) {
306 if (view == null) {
307 throw new IllegalArgumentException("view must not be null");
308 }
。。。。
372 IWindowSession windowlessSession = null;
373 // If there is a parent set, but we can't find it, it may be coming
385 if (windowlessSession == null) {
// 创建ViewRootImpl 对象，windowlessSession与分屏有关
386 root = new ViewRootImpl(view.getContext(), display);
387 } else {
388 root = new ViewRootImpl(view.getContext(), display,
389 windowlessSession);
390 }
// 给 ViewRootImpl 去设置params 参数
392 view.setLayoutParams(wparams);
393
394 mViews.add(view);
395 mRoots.add(root);
396 mParams.add(wparams);
397
398 // do this last because it fires off messages to start doing things
399 try {
// 去设置view
400 root.setView(view, wparams, panelParentView, userId);
401 } catch (RuntimeException e) {/frameworks/base/core/java/android/view/ViewRootImpl.java
1099 public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,
1100 int userId) {
1101 synchronized (this) {
1102 if (mView == null) {
1103 mView = view;
。。。。
// 向surfaceflinger 申请vsync ，准备绘制
1195 requestLayout();
1196 InputChannel inputChannel = null;
1197 if ((mWindowAttributes.inputFeatures
1198 & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
// 没有该属性，创建 InputChannel对象
1199 inputChannel = new InputChannel();
1200 }
。。。。
1212 try {
1213 mOrigWindowType = mWindowAttributes.type;
1214 mAttachInfo.mRecomputeGlobalAttributes = true;
1215 collectViewAttributes();
1216 adjustLayoutParamsForCompatibility(mWindowAttributes);
1217 controlInsetsForCompatibility(mWindowAttributes);
// 一、这里传入了空的 inputChannel，去与input 创建socket 通信。这里还去创建了 windowtoken、windowstate 等对象
1218 res = mWindowSession.addToDisplayAsUser(mWindow, mWindowAttributes,
1219 getHostVisibility(), mDisplay.getDisplayId(), userId,
1220 mInsetsController.getRequestedVisibilities(), inputChannel, mTempInsets,
1221 mTempControls);
// 二、创建service 服务端到客户端的回调
1325 if (inputChannel != null) {
1326 if (mInputQueueCallback != null) {
1327 mInputQueue = new InputQueue();
1328 mInputQueueCallback.onInputQueueCreated(mInputQueue);
1329 }
// 创建 WindowInputEventReceiver对象，looper 是主线程
1330 mInputEventReceiver = new WindowInputEventReceiver(inputChannel,
1331 Looper.myLooper());
1332
1333 if (ENABLE_INPUT_LATENCY_TRACKING && mAttachInfo.mThreadedRenderer != null) {
1334 InputMetricsListener listener = new InputMetricsListener();
1335 mHardwareRendererObserver = new HardwareRendererObserver(
1336 listener, listener.data, mHandler, true /*waitForPresentTime*/);
1337 mAttachInfo.mThreadedRenderer.addObserver(mHardwareRendererObserver);
1338 }
1339 }
1340
1341 view.assignParent(this);
1342 mAddedTouchMode = (res & WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE) != 0;
1343 mAppVisible = (res & WindowManagerGlobal.ADD_FLAG_APP_VISIBLE) != 0;
1344
1345 if (mAccessibilityManager.isEnabled()) {
1346 mAccessibilityInteractionConnectionManager.ensureConnection();
1347 }
1348
1349 if (view.getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
1350 view.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
1351 }
1352
// 设置input 事件接收后的回调链
1353 // Set up the input pipeline.
1354 CharSequence counterSuffix = attrs.getTitle();
1355 mSyntheticInputStage = new SyntheticInputStage();
1356 InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
1357 InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
1358 "aq:native-post-ime:" + counterSuffix);
1359 InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
1360 InputStage imeStage = new ImeInputStage(earlyPostImeStage,
1361 "aq:ime:" + counterSuffix);
1362 InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
1363 InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
1364 "aq:native-pre-ime:" + counterSuffix);
1365
1366 mFirstInputStage = nativePreImeStage;
1367 mFirstPostImeInputStage = earlyPostImeStage;
1368 mPendingInputEventQueueLengthCounterName = "aq:pending:" + counterSuffix;
1369
1370 AnimationHandler.requestAnimatorsEnabled(mAppVisible, this);
1371 }
1372 }一、传入空的 inputChannel，去与input 创建socket 通信。
调用mWindowSession.addToDisplay携带着InputChannel，addToDisplay最终调用到WMS的addwindow。
/frameworks/base/services/core/java/com/android/server/wm/Session.java
205 public int addToDisplayAsUser(IWindow window, WindowManager.LayoutParams attrs,
206 int viewVisibility, int displayId, int userId, InsetsVisibilities requestedVisibilities,
207 InputChannel outInputChannel, InsetsState outInsetsState,
208 InsetsSourceControl[] outActiveControls) {
209 return mService.addWindow(this, window, attrs, viewVisibility, displayId, userId,
210 requestedVisibilities, outInputChannel, outInsetsState, outActiveControls);
211 }/frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
449 public int addWindow(Session session, IWindow client, LayoutParams attrs, int viewVisibility,
1450 int displayId, int requestUserId, InsetsVisibilities requestedVisibilities,
1451 InputChannel outInputChannel, InsetsState outInsetsState,
1452 InsetsSourceControl[] outActiveControls) {
1453 Arrays.fill(outActiveControls, null);
1454 int[] appOp = new int[1];
1455 final boolean isRoundedCornerOverlay = (attrs.privateFlags
1456 & PRIVATE_FLAG_IS_ROUNDED_CORNERS_OVERLAY) != 0;
1457 int res = mPolicy.checkAddPermission(attrs.type, isRoundedCornerOverlay, attrs.packageName,
1458 appOp);
1459 if (res != ADD_OKAY) {
1460 return res;
1461 }
。。。。。。。。
1682 final boolean openInputChannels = (outInputChannel != null
1683 && (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0);
1684 if (openInputChannels) {
// 通过windowstate 去打开channel，给outInputChannel 赋值
1685 win.openInputChannel(outInputChannel);
1686 }
1687 /frameworks/base/services/core/java/com/android/server/wm/WindowState.java
2766 void openInputChannel(InputChannel outInputChannel) {
2767 if (mInputChannel != null) {
2768 throw new IllegalStateException("Window already has an input channel.");
2769 }
2770 String name = getName();
// 通过wms 的ims 去创建inputchannel
2771 mInputChannel = mWmService.mInputManager.createInputChannel(name);
2772 mInputChannelToken = mInputChannel.getToken();
2773 mInputWindowHandle.setToken(mInputChannelToken);
2774 mWmService.mInputToWindowMap.put(mInputChannelToken, this);
2775 if (outInputChannel != null) {
2776 mInputChannel.copyTo(outInputChannel);
2777 } else {
2778 // If the window died visible, we setup a fake input channel, so that taps
2779 // can still detected by input monitor channel, and we can relaunch the app.
2780 // Create fake event receiver that simply reports all events as handled.
2781 mDeadWindowEventReceiver = new DeadWindowEventReceiver(mInputChannel);
2782 }
2783 }/frameworks/base/services/core/java/com/android/server/input/InputManagerService.java
784 public InputChannel createInputChannel(String name) {
785 return mNative.createInputChannel(name);
786 }
// mNative 对象是 NativeImpl
406 NativeInputManagerService getNativeService(InputManagerService service) {
407 return new NativeInputManagerService.NativeImpl(service, mContext, mLooper.getQueue());
408 }/frameworks/base/services/core/java/com/android/server/input/NativeInputManagerService.java
194 class NativeImpl implements NativeInputManagerService {
195 /** Pointer to native input manager service object, used by native code. */
196 @SuppressWarnings({"unused", "FieldCanBeLocal"})
197 private final long mPtr;
198
199 NativeImpl(InputManagerService service, Context context, MessageQueue messageQueue) {
// 调用native 层初始化方法
200 mPtr = init(service, context, messageQueue);
201 }
// 调用native 层createInputChannel 方法
229 public native InputChannel createInputChannel(String name);
/frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp
2322 {"createInputChannel", "(Ljava/lang/String;)Landroid/view/InputChannel;",
2323 (void*)nativeCreateInputChannel},
1592
1593 static jobject nativeCreateInputChannel(JNIEnv* env, jobject nativeImplObj, jstring nameObj) {
1594 NativeInputManager* im = getNativeInputManager(env, nativeImplObj);
1595
1596 ScopedUtfChars nameChars(env, nameObj);
1597 std::string name = nameChars.c_str();
1598
// NativeInputManager 的 createInputChannel 方法
1599 base::Result<std::unique_ptr<InputChannel>> inputChannel = im->createInputChannel(name);
1600
1601 if (!inputChannel.ok()) {
1602 std::string message = inputChannel.error().message();
1603 message += StringPrintf(" Status=%d", static_cast<int>(inputChannel.error().code()));
1604 jniThrowRuntimeException(env, message.c_str());
1605 return nullptr;
1606 }
1607
// 回调java 层的方法
1608 jobject inputChannelObj =
1609 android_view_InputChannel_createJavaObject(env, std::move(*inputChannel));
1610 if (!inputChannelObj) {
1611 return nullptr;
1612 }
1613
1614 android_view_InputChannel_setDisposeCallback(env, inputChannelObj,
1615 handleInputChannelDisposed, im);
1616 return inputChannelObj;
1617 }
512 base::Result<std::unique_ptr<InputChannel>> NativeInputManager::createInputChannel(
513 const std::string& name) {
514 ATRACE_CALL();
// 调用InputDispatcher 的方法 createInputChannel
515 return mInputManager->getDispatcher().createInputChannel(name);
516 }/frameworks/native/services/inputflinger/dispatcher/InputDispatcher.cpp
5450 Result<std::unique_ptr<InputChannel>> InputDispatcher::createInputChannel(const std::string& name) {
5451 if (DEBUG_CHANNEL_CREATION) {
5452 ALOGD("channel '%s' ~ createInputChannel", name.c_str());
5453 }
5454
5455 std::unique_ptr<InputChannel> serverChannel;
5456 std::unique_ptr<InputChannel> clientChannel;
// InputChannel 去创建socket 通信
5457 status_t result = InputChannel::openInputChannelPair(name, serverChannel, clientChannel);
5458
5459 if (result) {
5460 return base::Error(result) << "Failed to open input channel pair with name " << name;
5461 }
5462
5463 { // acquire lock
5464 std::scoped_lock _l(mLock);
5465 const sp<IBinder>& token = serverChannel->getConnectionToken();
5466 int fd = serverChannel->getFd();
// 创建服务器端的 Connection，serverChannel作为参数
5467 sp<Connection> connection =
5468 new Connection(std::move(serverChannel), false /*monitor*/, mIdGenerator);
5469
5470 if (mConnectionsByToken.find(token) != mConnectionsByToken.end()) {
5471 ALOGE("Created a new connection, but the token %p is already known", token.get());
5472 }
// 将token作为客户端的标志值保存到 mConnectionsByToken，在事件分发的时候可以使用
5473 mConnectionsByToken.emplace(token, connection);
5474
5475 std::function<int(int events)> callback = std::bind(&InputDispatcher::handleReceiveCallback,
5476 this, std::placeholders::_1, token);
5477
// 将 handleReceiveCallback 函数增加到fd 的监听中，应用客户端与input 服务端通信的时候，会回调 handleReceiveCallback
5478 mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, new LooperEventCallback(callback), nullptr);
5479 } // release lock
5480
5481 // Wake the looper because some connections have changed.
5482 mLooper->wake();
// 这里返回客户端inputchannel 给应用
5483 return clientChannel;
5484 }调用socketpair函数创建一对相互连接的socket，然后创建了一对InputChannel，分别持有一个socket，一个作为客户端一个作为服务端，这样分别持有这两个InputChannel的两端就可以通过socket通信了。
// =========InputChannel 去创建socket 通信========
334 status_t InputChannel::openInputChannelPair(const std::string& name,
335 std::unique_ptr<InputChannel>& outServerChannel,
336 std::unique_ptr<InputChannel>& outClientChannel) {
337 int sockets[2];
// 创建socket
338 if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) {
339 status_t result = -errno;
340 ALOGE("channel '%s' ~ Could not create socket pair. errno=%s(%d)", name.c_str(),
341 strerror(errno), errno);
342 outServerChannel.reset();
343 outClientChannel.reset();
344 return result;
345 }
346
347 int bufferSize = SOCKET_BUFFER_SIZE;
// 设置双向通信
348 setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
349 setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
350 setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
351 setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
352
// 服务器端和客户端都是使用相同的token
353 sp<IBinder> token = new BBinder();
354
355 std::string serverChannelName = name + " (server)";
356 android::base::unique_fd serverFd(sockets[0]);
// 创建服务器端的 InputChannel 对象
357 outServerChannel = InputChannel::create(serverChannelName, std::move(serverFd), token);
358
359 std::string clientChannelName = name + " (client)";
360 android::base::unique_fd clientFd(sockets[1]);
// 创建客户器端的 InputChannel 对象
361 outClientChannel = InputChannel::create(clientChannelName, std::move(clientFd), token);
362 return OK;
363 }
309 std::unique_ptr<InputChannel> InputChannel::create(const std::string& name,
310 android::base::unique_fd fd, sp<IBinder> token) {
311 const int result = fcntl(fd, F_SETFL, O_NONBLOCK);
312 if (result != 0) {
313 LOG_ALWAYS_FATAL("channel '%s' ~ Could not make socket non-blocking: %s", name.c_str(),
314 strerror(errno));
315 return nullptr;
316 }
317 // using 'new' to access a non-public constructor
318 return std::unique_ptr<InputChannel>(new InputChannel(name, std::move(fd), token));
319 }
/frameworks/base/services/core/java/com/android/server/wm/WindowState.java
2766 void openInputChannel(InputChannel outInputChannel) {
2767 if (mInputChannel != null) {
2768 throw new IllegalStateException("Window already has an input channel.");
2769 }
2770 String name = getName();
// 最终获取到创建的 nputchannel
2771 mInputChannel = mWmService.mInputManager.createInputChannel(name);
// 获取到token，该token 的值与 服务器端ims 的值是一致的。可以一一对应socket 通信
2772 mInputChannelToken = mInputChannel.getToken();
// 将其设置给 InputWindowHandle
2773 mInputWindowHandle.setToken(mInputChannelToken);
2774 mWmService.mInputToWindowMap.put(mInputChannelToken, this);
2775 if (outInputChannel != null) {
// 最后将其拷贝给 mInputChannel
2776 mInputChannel.copyTo(outInputChannel);
2777 } else {
2778 // If the window died visible, we setup a fake input channel, so that taps
2779 // can still detected by input monitor channel, and we can relaunch the app.
2780 // Create fake event receiver that simply reports all events as handled.
2781 mDeadWindowEventReceiver = new DeadWindowEventReceiver(mInputChannel);
2782 }
2783 }二、创建service 服务端到客户端的回调
/frameworks/base/core/java/android/view/ViewRootImpl.java
// 创建 WindowInputEventReceiver对象，looper 是主线程
1330 mInputEventReceiver = new WindowInputEventReceiver(inputChannel,
1331 Looper.myLooper());
// 创建 WindowInputEventReceiver对象，继承了 InputEventReceiver对象
8953 final class WindowInputEventReceiver extends InputEventReceiver {
8954 public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
8955 super(inputChannel, looper);
8956 }
8957
// 会回调下列的方法，然后走调用链 enqueueInputEvent
8958 @Override
8959 public void onInputEvent(InputEvent event) {
8960 Trace.traceBegin(Trace.TRACE_TAG_VIEW, "processInputEventForCompatibility");
8961 List<InputEvent> processedEvents;
8962 try {
8963 processedEvents =
8964 mInputCompatProcessor.processInputEventForCompatibility(event);
8965 } finally {
8966 Trace.traceEnd(Trace.TRACE_TAG_VIEW);
8967 }
8968 if (processedEvents != null) {
8969 if (processedEvents.isEmpty()) {
8970 // InputEvent consumed by mInputCompatProcessor
8971 finishInputEvent(event, true);
8972 } else {
8973 for (int i = 0; i < processedEvents.size(); i++) {
8974 enqueueInputEvent(
8975 processedEvents.get(i), this,
8976 QueuedInputEvent.FLAG_MODIFIED_FOR_COMPATIBILITY, true);
8977 }
8978 }
8979 } else {
8980 enqueueInputEvent(event, this, 0, true);
8981 }
8982 }
// InputEventReceiver对象的构造方法
/frameworks/base/core/java/android/view/InputEventReceiver.java
69 public InputEventReceiver(InputChannel inputChannel, Looper looper) {
70 if (inputChannel == null) {
71 throw new IllegalArgumentException("inputChannel must not be null");
72 }
73 if (looper == null) {
74 throw new IllegalArgumentException("looper must not be null");
75 }
76
77 mInputChannel = inputChannel;
78 mMessageQueue = looper.getQueue();
// 调用native 层的初始化方法
79 mReceiverPtr = nativeInit(new WeakReference<InputEventReceiver>(this),
80 inputChannel, mMessageQueue);
81
82 mCloseGuard.open("InputEventReceiver.dispose");
83 }/frameworks/base/core/jni/android_view_InputEventReceiver.cpp
493 static jlong nativeInit(JNIEnv* env, jclass clazz, jobject receiverWeak,
494 jobject inputChannelObj, jobject messageQueueObj) {
495 std::shared_ptr<InputChannel> inputChannel =
496 android_view_InputChannel_getInputChannel(env, inputChannelObj);
497 if (inputChannel == nullptr) {
498 jniThrowRuntimeException(env, "InputChannel is not initialized.");
499 return 0;
500 }
501
502 sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);
503 if (messageQueue == nullptr) {
504 jniThrowRuntimeException(env, "MessageQueue is not initialized.");
505 return 0;
506 }
507
// 创建 NativeInputEventReceiver 对象
508 sp<NativeInputEventReceiver> receiver = new NativeInputEventReceiver(env,
509 receiverWeak, inputChannel, messageQueue);
// 初始化
510 status_t status = receiver->initialize();
511 if (status) {
512 std::string message = android::base::
513 StringPrintf("Failed to initialize input event receiver. status=%s(%d)",
514 statusToString(status).c_str(), status);
515 jniThrowRuntimeException(env, message.c_str());
516 return 0;
517 }
518
519 receiver->incStrong(gInputEventReceiverClassInfo.clazz); // retain a reference for the object
520 return reinterpret_cast<jlong>(receiver.get());
521 }
124 NativeInputEventReceiver::NativeInputEventReceiver(
125 JNIEnv* env, jobject receiverWeak, const std::shared_ptr<InputChannel>& inputChannel,
126 const sp<MessageQueue>& messageQueue)
127 : mReceiverWeakGlobal(env->NewGlobalRef(receiverWeak)),
128 mInputConsumer(inputChannel),
129 mMessageQueue(messageQueue),
130 mBatchedInputEventPending(false),
131 mFdEvents(0) {
132 if (kDebugDispatchCycle) {
133 ALOGD("channel '%s' ~ Initializing input event receiver.", getInputChannelName().c_str());
134 }
135 }
// 初始化的方法
142 status_t NativeInputEventReceiver::initialize() {
143 setFdEvents(ALOOPER_EVENT_INPUT);
144 return OK;
145 }
184 void NativeInputEventReceiver::setFdEvents(int events) {
185 if (mFdEvents != events) {
186 mFdEvents = events;
// events 是 ALOOPER_EVENT_INPUT
187 int fd = mInputConsumer.getChannel()->getFd();
188 if (events) {
// 在Looper 代码中，如果有socket 通信，会回调 handleEvent
189 mMessageQueue->getLooper()->addFd(fd, 0, events, this, nullptr);
190 } else {
191 mMessageQueue->getLooper()->removeFd(fd);
192 }
193 }
194 }
263 int NativeInputEventReceiver::handleEvent(int receiveFd, int events, void* data) {
264 // Allowed return values of this function as documented in LooperCallback::handleEvent
265 constexpr int REMOVE_CALLBACK = 0;
266 constexpr int KEEP_CALLBACK = 1;
267
268 if (events & (ALOOPER_EVENT_ERROR | ALOOPER_EVENT_HANGUP)) {
269 // This error typically occurs when the publisher has closed the input channel
270 // as part of removing a window or finishing an IME session, in which case
271 // the consumer will soon be disposed as well.
272 if (kDebugDispatchCycle) {
273 ALOGD("channel '%s' ~ Publisher closed input channel or an error occurred. events=0x%x",
274 getInputChannelName().c_str(), events);
275 }
276 return REMOVE_CALLBACK;
277 }
278
// 是下列的event，去消费input事件
279 if (events & ALOOPER_EVENT_INPUT) {
280 JNIEnv* env = AndroidRuntime::getJNIEnv();
281 status_t status = consumeEvents(env, false /*consumeBatches*/, -1, nullptr);
282 mMessageQueue->raiseAndClearException(env, "handleReceiveCallback");
283 return status == OK || status == NO_MEMORY ? KEEP_CALLBACK : REMOVE_CALLBACK;
284 }总结：
- 创建了一对相互连接的Socket，用来通信
- 创建了一对InputChannel，分别持有一个socket，使InputChannel成为实现两端通信的信使。
- 两个InputChannel分别作为客户端channel和服务端channel，服务端channel给InputDispatcher持有，客户端channel给InputEventReceiver持有。
- 两个socket的fd分别注册到对应端的Looper，有数据传输会唤醒对端处理。
