// SystemServer.java
private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
            // ..
    // 1. 創(chuàng)建
    inputManager = new InputManagerService(context);
    // 注冊(cè)服務(wù)    
    ServiceManager.addService(Context.INPUT_SERVICE, inputManager,
                    /* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
    // 保存 wms 的回調(diào)
    inputManager.setWindowManagerCallbacks(wm.getInputManagerCallback());
    // 2. 啟動(dòng)
    inputManager.start();    
    try {
        // 3. 就緒
        if (inputManagerF != null) {
            inputManagerF.systemRunning();
        }
    } catch (Throwable e) {
        reportWtf("Notifying InputManagerService running", e);
    }
    // ...
}

// InputManagerService.java
public InputManagerService(Context context) {
    this.mContext = context;
    this.mHandler = new InputManagerHandler(DisplayThread.get().getLooper());
    // 配置為空
    mStaticAssociations = loadStaticInputPortAssociations();
    // 默認(rèn) false
    mUseDevInputEventForAudioJack =
            context.getResources().getBoolean(R.bool.config_useDevInputEventForAudioJack);
    // 1. 底層進(jìn)行初始化
    // mPtr 指向底層創(chuàng)建的 NativeInputManager 對(duì)象
    mPtr = nativeInit(this, mContext, mHandler.getLooper().getQueue());
    // 空
    String doubleTouchGestureEnablePath = context.getResources().getString(
            R.string.config_doubleTouchGestureEnableFile);
    // null
    mDoubleTouchGestureEnableFile = TextUtils.isEmpty(doubleTouchGestureEnablePath) ? null :
        new File(doubleTouchGestureEnablePath);
    LocalServices.addService(InputManagerInternal.class, new LocalService());
}

// com_android_server_input_InputManagerService.cpp
static jlong nativeInit(JNIEnv* env, jclass /* clazz */,
        jobject serviceObj, jobject contextObj, jobject messageQueueObj) {
    // 從Java層的MessageQueue中獲取底層映射的MessageQueue
    sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);
    if (messageQueue == nullptr) {
        jniThrowRuntimeException(env, "MessageQueue is not initialized.");
        return 0;
    }
    // 創(chuàng)建 NativeInputManager
    NativeInputManager* im = new NativeInputManager(contextObj, serviceObj,
            messageQueue->getLooper());
    im->incStrong(0);
    // 返回指向 NativeInputManager 對(duì)象的指針
    return reinterpret_cast<jlong>(im);
}

// com_android_server_input_InputManagerService.cpp
NativeInputManager::NativeInputManager(jobject contextObj,
        jobject serviceObj, const sp<Looper>& looper) :
        mLooper(looper), mInteractive(true) {
    JNIEnv* env = jniEnv();
    // 1.保存上層的InputManagerService對(duì)象
    mServiceObj = env->NewGlobalRef(serviceObj);
    // 2. 初始化一些參數(shù)
    {
        AutoMutex _l(mLock);
        // mLocked 的類型是 struct Locked，這里初始化了一些參數(shù)
        // 這些參數(shù)會(huì)被上層改變
        mLocked.systemUiVisibility = ASYSTEM_UI_VISIBILITY_STATUS_BAR_VISIBLE;
        mLocked.pointerSpeed = 0;
        mLocked.pointerGesturesEnabled = true;
        mLocked.showTouches = false;
        mLocked.pointerCapture = false;
        mLocked.pointerDisplayId = ADISPLAY_ID_DEFAULT;
    }
    mInteractive = true;
    // 3.創(chuàng)建并注冊(cè)服務(wù) InputManager
    mInputManager = new InputManager(this, this);
    defaultServiceManager()->addService(String16("inputflinger"),
            mInputManager, false);
}

// InputManager.cpp
InputManager::InputManager(
        const sp<InputReaderPolicyInterface>& readerPolicy,
        const sp<InputDispatcherPolicyInterface>& dispatcherPolicy) {
    // 1. 創(chuàng)建InputDispatcher對(duì)象，使用 InputDispatcherPolicyInterface 接口
    mDispatcher = createInputDispatcher(dispatcherPolicy);
    // 2. 創(chuàng)建InputClassifier對(duì)象，使用 InputListenerInterface
    mClassifier = new InputClassifier(mDispatcher);
    // 3. 創(chuàng)建InputReader對(duì)象，使用 InputReaderPolicyInterface 和 InputListenerInterface
    mReader = createInputReader(readerPolicy, mClassifier);
}
// InputDispatcherFactory.cpp
sp<InputDispatcherInterface> createInputDispatcher(
        const sp<InputDispatcherPolicyInterface>& policy) {
    return new android::inputdispatcher::InputDispatcher(policy);
}
// InputReaderFactory.cpp
sp<InputReaderInterface> createInputReader(const sp<InputReaderPolicyInterface>& policy,
                                           const sp<InputListenerInterface>& listener) {
    return new InputReader(std::make_unique<EventHub>(), policy, listener);
}

// InputManagerService.java
    public void start() {
        Slog.i(TAG, "Starting input manager");
        // 1.啟動(dòng)native層
        nativeStart(mPtr);
        // Add ourself to the Watchdog monitors.
        Watchdog.getInstance().addMonitor(this);
        // 2.監(jiān)聽(tīng)數(shù)據(jù)庫(kù)，當(dāng)值發(fā)生改變時(shí)，通過(guò) native 層
        // 監(jiān)聽(tīng)Settings.System.POINTER_SPEED，這個(gè)表示手指的速度
        registerPointerSpeedSettingObserver();
        // 監(jiān)聽(tīng)Settings.System.SHOW_TOUCHES，這個(gè)表示是否在屏幕上顯示觸摸坐標(biāo)
        registerShowTouchesSettingObserver();
        // 監(jiān)聽(tīng)Settings.Secure.ACCESSIBILITY_LARGE_POINTER_ICON
        registerAccessibilityLargePointerSettingObserver();
        // 監(jiān)聽(tīng)Settings.Secure.LONG_PRESS_TIMEOUT，這個(gè)多少毫秒觸發(fā)長(zhǎng)按事件
        registerLongPressTimeoutObserver();
        // 監(jiān)聽(tīng)用戶切換
        mContext.registerReceiver(new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                updatePointerSpeedFromSettings();
                updateShowTouchesFromSettings();
                updateAccessibilityLargePointerFromSettings();
                updateDeepPressStatusFromSettings("user switched");
            }
        }, new IntentFilter(Intent.ACTION_USER_SWITCHED), null, mHandler);
        // 3. 從數(shù)據(jù)庫(kù)獲取值，并傳遞給 native 層
        updatePointerSpeedFromSettings();
        updateShowTouchesFromSettings();
        updateAccessibilityLargePointerFromSettings();
        updateDeepPressStatusFromSettings("just booted");
    }

// com_android_server_input_InputManagerService.cpp
static void nativeStart(JNIEnv* env, jclass /* clazz */, jlong ptr) {
    NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);
    // 調(diào)用InputManager::start()
    status_t result = im->getInputManager()->start();
    if (result) {
        jniThrowRuntimeException(env, "Input manager could not be started.");
    }
}

status_t InputManager::start() {
    // 啟動(dòng) Dispatcher
    status_t result = mDispatcher->start();
    if (result) {
        ALOGE("Could not start InputDispatcher thread due to error %d.", result);
        return result;
    }
    // 啟動(dòng) InputReader
    result = mReader->start();
    if (result) {
        ALOGE("Could not start InputReader due to error %d.", result);
        mDispatcher->stop();
        return result;
    }
    return OK;
}

//InputThread.cpp
InputThread::InputThread(std::string name, std::function<void()> loop, std::function<void()> wake)
     : mName(name), mThreadWake(wake) {
   mThread = new InputThreadImpl(loop);
   mThread->run(mName.c_str(), ANDROID_PRIORITY_URGENT_DISPLAY);
}

//InputThread.cpp
class InputThreadImpl : public Thread {
public:
    explicit InputThreadImpl(std::function<void()> loop)
          : Thread(/* canCallJava */ true), mThreadLoop(loop) {}
    ~InputThreadImpl() {}
private:
    std::function<void()> mThreadLoop;
    bool threadLoop() override {
        mThreadLoop();
        return true;
    }
};

// InputReader.cpp
status_t InputReader::start() {
    if (mThread) {
        return ALREADY_EXISTS;
    }
    // 線程啟動(dòng)后，循環(huán)調(diào)用 loopOnce()
    mThread = std::make_unique<InputThread>(
            "InputReader", [this]() { loopOnce(); }, [this]() { mEventHub->wake(); });
    return OK;
}
// InputDispatcher.cpp
status_t InputDispatcher::start() {
    if (mThread) {
        return ALREADY_EXISTS;
    }
    // 線程啟動(dòng)后，循環(huán)調(diào)用 dispatchOnce()
    mThread = std::make_unique<InputThread>(
            "InputDispatcher", [this]() { dispatchOnce(); }, [this]() { mLooper->wake(); });
    return OK;
}

// InputManagerService.java
public void systemRunning() {
    mNotificationManager = (NotificationManager)mContext.getSystemService(
            Context.NOTIFICATION_SERVICE);
    synchronized (mLidSwitchLock) {
        mSystemReady = true;
        // Send the initial lid switch state to any callback registered before the system was
        // ready.
        int switchState = getSwitchState(-1 /* deviceId */, InputDevice.SOURCE_ANY, SW_LID);
        for (int i = 0; i < mLidSwitchCallbacks.size(); i++) {
            LidSwitchCallback callback = mLidSwitchCallbacks.get(i);
            callback.notifyLidSwitchChanged(0 /* whenNanos */, switchState == KEY_STATE_UP);
        }
    }
    // 監(jiān)聽(tīng)廣播，通知底層加載鍵盤布局
    IntentFilter filter = new IntentFilter(Intent.ACTION_PACKAGE_ADDED);
    filter.addAction(Intent.ACTION_PACKAGE_REMOVED);
    filter.addAction(Intent.ACTION_PACKAGE_CHANGED);
    filter.addAction(Intent.ACTION_PACKAGE_REPLACED);
    filter.addDataScheme("package");
    mContext.registerReceiver(new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            updateKeyboardLayouts();
        }
    }, filter, null, mHandler);
    // 監(jiān)聽(tīng)廣播，通知底層加載設(shè)備別名
    filter = new IntentFilter(BluetoothDevice.ACTION_ALIAS_CHANGED);
    mContext.registerReceiver(new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            reloadDeviceAliases();
        }
    }, filter, null, mHandler);
    // 直接通知一次底層加載鍵盤布局和加載設(shè)備別名
    mHandler.sendEmptyMessage(MSG_RELOAD_DEVICE_ALIASES);
    mHandler.sendEmptyMessage(MSG_UPDATE_KEYBOARD_LAYOUTS);
    if (mWiredAccessoryCallbacks != null) {
        mWiredAccessoryCallbacks.systemReady();
    }
}
private void reloadKeyboardLayouts() {
    nativeReloadKeyboardLayouts(mPtr);
}
private void reloadDeviceAliases() {
    nativeReloadDeviceAliases(mPtr);
}