Input系统—InputReader线程

Posted by Gityuan on December 11, 2016

基于Android 6.0源码, 分析InputManagerService的启动过程

一. InputReader起点

上一篇文章Input系统—启动篇,介绍IMS服务的启动过程会创建两个native线程,分别是InputReader,InputDispatcher. 接下来从InputReader线程的执行过程从threadLoop为起点开始分析。

1.1 threadLoop

[-> InputReader.cpp]

bool InputReaderThread::threadLoop() {
    mReader->loopOnce(); //【见小节1.2】
    return true;
}

threadLoop返回值true代表的是会不断地循环调用loopOnce()。另外,如果当返回值为false则会 退出循环。整个过程是不断循环的地调用InputReader的loopOnce()方法,先来回顾一下InputReader对象构造方法。

1.2 loopOnce

[-> InputReader.cpp]

void InputReader::loopOnce() {
    ...
    {
        AutoMutex _l(mLock);
        uint32_t changes = mConfigurationChangesToRefresh;
        if (changes) {
            timeoutMillis = 0;
            ...
        } else if (mNextTimeout != LLONG_MAX) {
            nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
            timeoutMillis = toMillisecondTimeoutDelay(now, mNextTimeout);
        }
    }

    //从EventHub读取事件,其中EVENT_BUFFER_SIZE = 256【见小节2.1】
    size_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);

    { // acquire lock
        AutoMutex _l(mLock);
         mReaderIsAliveCondition.broadcast();
        if (count) { //处理事件【见小节3.1】
            processEventsLocked(mEventBuffer, count);
        }
        if (oldGeneration != mGeneration) {
            inputDevicesChanged = true;
            getInputDevicesLocked(inputDevices);
        }
        ...
    } // release lock


    if (inputDevicesChanged) { //输入设备发生改变
        mPolicy->notifyInputDevicesChanged(inputDevices);
    }
    //发送事件到nputDispatcher【见小节4.1】
    mQueuedListener->flush();
}

二. EventHub

2.1 getEvents

[-> EventHub.cpp]

size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSize) {
    AutoMutex _l(mLock); //加锁

    struct input_event readBuffer[bufferSize];
    RawEvent* event = buffer; //原始事件
    size_t capacity = bufferSize; //容量大小为256
    bool awoken = false;
    for (;;) {
        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
        ...

        if (mNeedToScanDevices) {
            mNeedToScanDevices = false;
            scanDevicesLocked(); //扫描设备【见小节2.2】
            mNeedToSendFinishedDeviceScan = true;
        }

        while (mOpeningDevices != NULL) {
            Device* device = mOpeningDevices;
            mOpeningDevices = device->next;
            event->when = now;
            event->deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;
            event->type = DEVICE_ADDED; //添加设备的事件
            event += 1;
            mNeedToSendFinishedDeviceScan = true;
            if (--capacity == 0) {
                break;
            }
        }
        ...

        bool deviceChanged = false;
        while (mPendingEventIndex < mPendingEventCount) {
            //从mPendingEventItems读取事件项
            const struct epoll_event& eventItem = mPendingEventItems[mPendingEventIndex++];
            ...
            //获取设备ID所对应的device
            ssize_t deviceIndex = mDevices.indexOfKey(eventItem.data.u32);
            Device* device = mDevices.valueAt(deviceIndex);
            if (eventItem.events & EPOLLIN) {
                //从设备不断读取事件,放入到readBuffer
                int32_t readSize = read(device->fd, readBuffer,
                        sizeof(struct input_event) * capacity);

                if (readSize == 0 || (readSize < 0 && errno == ENODEV)) {
                    deviceChanged = true;
                    closeDeviceLocked(device);//设备已被移除则执行关闭操作
                } else if (readSize < 0) {
                    ...
                } else if ((readSize % sizeof(struct input_event)) != 0) {
                    ...
                } else {
                    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++) {
                        //获取readBuffer的数据
                        struct input_event& iev = readBuffer[i];
                        //将input_event信息, 封装成RawEvent
                        event->when = nsecs_t(iev.time.tv_sec) * 1000000000LL
                                + nsecs_t(iev.time.tv_usec) * 1000LL;
                        event->deviceId = deviceId;
                        event->type = iev.type;
                        event->code = iev.code;
                        event->value = iev.value;
                        event += 1;
                        capacity -= 1;
                    }
                    if (capacity == 0) {
                        mPendingEventIndex -= 1;
                        break;
                    }
                }
            }
            ...
        }
        ...
        mLock.unlock(); //poll之前先释放锁
        //等待input事件的到来
        int pollResult = epoll_wait(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis);
        ...
        mLock.lock(); //poll之后再次请求锁

        if (pollResult < 0) { //出现错误
            mPendingEventCount = 0;
            if (errno != EINTR) {
                usleep(100000); //系统发生错误则休眠1s
            }
        } else {
            mPendingEventCount = size_t(pollResult);
        }
    }

    return event - buffer; //返回所读取的事件个数
}

EventHub采用INotify + epoll机制实现监听目录/dev/input下的设备节点,经过EventHub将input_event结构体 + deviceId 转换成RawEvent结构体,如下:

2.1.1 RawEvent

[-> InputEventReader.h]

struct input_event {
 struct timeval time; //事件发生的时间点
 __u16 type;
 __u16 code;
 __s32 value;
};

struct RawEvent {
    nsecs_t when; //事件发生的时间店
    int32_t deviceId; //产生事件的设备Id
    int32_t type; // 事件类型
    int32_t code;
    int32_t value;
};

此处事件类型:

  • DEVICE_ADDED(添加)
  • DEVICE_REMOVED(删除)
  • FINISHED_DEVICE_SCAN(扫描完成)
  • type<FIRST_SYNTHETIC_EVENT(其他事件)

getEvents()已完成转换事件转换工作, 接下来,顺便看看设备扫描过程.

2.2 设备扫描

2.2.1 scanDevicesLocked

void EventHub::scanDevicesLocked() {
    //此处DEVICE_PATH="/dev/input"【见小节2.3】
    status_t res = scanDirLocked(DEVICE_PATH);
    ...
}

2.2.2 scanDirLocked

status_t EventHub::scanDirLocked(const char *dirname)
{
    char devname[PATH_MAX];
    char *filename;
    DIR *dir;
    struct dirent *de;
    dir = opendir(dirname);

    strcpy(devname, dirname);
    filename = devname + strlen(devname);
    *filename++ = '/';
    //读取/dev/input/目录下所有的设备节点
    while((de = readdir(dir))) {
        if(de->d_name[0] == '.' &&
           (de->d_name[1] == '\0' ||
            (de->d_name[1] == '.' && de->d_name[2] == '\0')))
            continue;
        strcpy(filename, de->d_name);
        //打开相应的设备节点【2.2.3】
        openDeviceLocked(devname);
    }
    closedir(dir);
    return 0;
}

2.2.3 openDeviceLocked

status_t EventHub::openDeviceLocked(const char *devicePath) {
    char buffer[80];
    //打开设备文件
    int fd = open(devicePath, O_RDWR | O_CLOEXEC);
    InputDeviceIdentifier identifier;
    //获取设备名
    if(ioctl(fd, EVIOCGNAME(sizeof(buffer) - 1), &buffer) < 1){
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.name.setTo(buffer);
    }

    identifier.bus = inputId.bustype;
    identifier.product = inputId.product;
    identifier.vendor = inputId.vendor;
    identifier.version = inputId.version;

    //获取设备物理地址
    if(ioctl(fd, EVIOCGPHYS(sizeof(buffer) - 1), &buffer) < 1) {
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.location.setTo(buffer);
    }

    //获取设备唯一ID
    if(ioctl(fd, EVIOCGUNIQ(sizeof(buffer) - 1), &buffer) < 1) {
    } else {
        buffer[sizeof(buffer) - 1] = '\0';
        identifier.uniqueId.setTo(buffer);
    }
    //将identifier信息填充到fd
    assignDescriptorLocked(identifier);
    //设置fd为非阻塞方式
    fcntl(fd, F_SETFL, O_NONBLOCK);

    //获取设备ID,分配设备对象内存
    int32_t deviceId = mNextDeviceId++;
    Device* device = new Device(fd, deviceId, String8(devicePath), identifier);
    ...

    //注册epoll
    struct epoll_event eventItem;
    memset(&eventItem, 0, sizeof(eventItem));
    eventItem.events = EPOLLIN;
    if (mUsingEpollWakeup) {
        eventItem.events |= EPOLLWAKEUP;
    }
    eventItem.data.u32 = deviceId;
    if (epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, &eventItem)) {
        delete device; //添加失败则删除该设备
        return -1;
    }
    ...
    //【见小节2.2.4】
    addDeviceLocked(device);
}

2.2.4 addDeviceLocked

void EventHub::addDeviceLocked(Device* device) {
    mDevices.add(device->id, device); //添加到mDevices队列
    device->next = mOpeningDevices;
    mOpeningDevices = device;
}

介绍了EventHub从设备节点获取事件的流程,当收到事件后接下里便开始处理事件。

三. InputReader

3.1 processEventsLocked

[-> InputReader.cpp]

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;
            while (batchSize < count) {
                if (rawEvent[batchSize].type >= EventHubInterface::FIRST_SYNTHETIC_EVENT
                        || rawEvent[batchSize].deviceId != deviceId) {
                    break;
                }
                batchSize += 1; //同一设备的事件打包处理
            }
            //数据事件的处理【见小节3.3】
            processEventsForDeviceLocked(deviceId, rawEvent, batchSize);
        } else {
            switch (rawEvent->type) {
            case EventHubInterface::DEVICE_ADDED:
                //设备添加【见小节3.2】
                addDeviceLocked(rawEvent->when, rawEvent->deviceId);
                break;
            case EventHubInterface::DEVICE_REMOVED:
                //设备移除
                removeDeviceLocked(rawEvent->when, rawEvent->deviceId);
                break;
            case EventHubInterface::FINISHED_DEVICE_SCAN:
                //设备扫描完成
                handleConfigurationChangedLocked(rawEvent->when);
                break;
            default:
                ALOG_ASSERT(false);//不会发生
                break;
            }
        }
        count -= batchSize;
        rawEvent += batchSize;
    }
}

事件处理总共有下几类类型:

  • DEVICE_ADDED(设备增加), [见小节3.2]
  • DEVICE_REMOVED(设备移除)
  • FINISHED_DEVICE_SCAN(设备扫描完成)
  • 数据事件[见小节3.4]

先来说说DEVICE_ADDED设备增加的过程。

3.2 设备增加

3.2.1 addDeviceLocked

void InputReader::addDeviceLocked(nsecs_t when, int32_t deviceId) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    if (deviceIndex >= 0) {
        return; //已添加的相同设备则不再添加
    }

    InputDeviceIdentifier identifier = mEventHub->getDeviceIdentifier(deviceId);
    uint32_t classes = mEventHub->getDeviceClasses(deviceId);
    int32_t controllerNumber = mEventHub->getDeviceControllerNumber(deviceId);
    //【见小节3.2.2】
    InputDevice* device = createDeviceLocked(deviceId, controllerNumber, identifier, classes);
    device->configure(when, &mConfig, 0);
    device->reset(when);
    mDevices.add(deviceId, device); //添加设备到mDevices
    ...
}

3.2.2 createDeviceLocked

InputDevice* InputReader::createDeviceLocked(int32_t deviceId, int32_t controllerNumber,
        const InputDeviceIdentifier& identifier, uint32_t classes) {
    //创建InputDevice对象
    InputDevice* device = new InputDevice(&mContext, deviceId, bumpGenerationLocked(),
            controllerNumber, identifier, classes);
    ...

    //获取键盘源类型
    uint32_t keyboardSource = 0;
    int32_t keyboardType = AINPUT_KEYBOARD_TYPE_NON_ALPHABETIC;
    if (classes & INPUT_DEVICE_CLASS_KEYBOARD) {
        keyboardSource |= AINPUT_SOURCE_KEYBOARD;
    }
    if (classes & INPUT_DEVICE_CLASS_ALPHAKEY) {
        keyboardType = AINPUT_KEYBOARD_TYPE_ALPHABETIC;
    }
    if (classes & INPUT_DEVICE_CLASS_DPAD) {
        keyboardSource |= AINPUT_SOURCE_DPAD;
    }
    if (classes & INPUT_DEVICE_CLASS_GAMEPAD) {
        keyboardSource |= AINPUT_SOURCE_GAMEPAD;
    }

    //添加键盘类设备InputMapper
    if (keyboardSource != 0) {
        device->addMapper(new KeyboardInputMapper(device, keyboardSource, keyboardType));
    }

    //添加鼠标类设备InputMapper
    if (classes & INPUT_DEVICE_CLASS_CURSOR) {
        device->addMapper(new CursorInputMapper(device));
    }

    //添加触摸屏设备InputMapper
    if (classes & INPUT_DEVICE_CLASS_TOUCH_MT) {
        device->addMapper(new MultiTouchInputMapper(device));
    } else if (classes & INPUT_DEVICE_CLASS_TOUCH) {
        device->addMapper(new SingleTouchInputMapper(device));
    }
    ...
    return device;
}

该方法主要功能:

  • 创建InputDevice对象,将InputReader的mContext赋给InputDevice对象所对应的变量
  • 根据设备类型来创建并添加相对应的InputMapper,同时设置mContext.

input设备类型有很多种,以上代码只列举部分常见的设备以及相应的InputMapper:

  • 键盘类设备:KeyboardInputMapper
  • 触摸屏设备:MultiTouchInputMapper或SingleTouchInputMapper
  • 鼠标类设备:CursorInputMapper

介绍完设备增加过程,继续回到[小节3.1]除了设备的增删,更常见事件便是数据事件,那么接下来介绍数据事件的 处理过程。

3.3 事件处理

3.3.1 processEventsForDeviceLocked

void InputReader::processEventsForDeviceLocked(int32_t deviceId,
        const RawEvent* rawEvents, size_t count) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    ...

    InputDevice* device = mDevices.valueAt(deviceIndex);
    if (device->isIgnored()) {
        return; //可忽略则直接返回
    }
    //【见小节3.3.2】
    device->process(rawEvents, count);
}

3.3.2 InputDevice.process

void InputDevice::process(const RawEvent* rawEvents, size_t count) {
    size_t numMappers = mMappers.size();
    for (const RawEvent* rawEvent = rawEvents; count--; rawEvent++) {
        if (mDropUntilNextSync) {
            if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
                mDropUntilNextSync = false;
            }
        } else if (rawEvent->type == EV_SYN && rawEvent->code == SYN_DROPPED) {
            mDropUntilNextSync = true;
            reset(rawEvent->when);
        } else {
            for (size_t i = 0; i < numMappers; i++) {
                InputMapper* mapper = mMappers[i];
                //调用具体mapper来处理【见小节3.4】
                mapper->process(rawEvent);
            }
        }
    }
}

小节[3.2]createDeviceLocked创建设备并添加InputMapper,提到会有多种InputMapper。 这里以KeyboardInputMapper(按键事件)为例来展开说明

3.4 按键事件处理

3.4.1 KeyboardInputMapper.process

[-> InputReader.cpp ::KeyboardInputMapper]

void KeyboardInputMapper::process(const RawEvent* rawEvent) {
    switch (rawEvent->type) {
    case EV_KEY: {
        int32_t scanCode = rawEvent->code;
        int32_t usageCode = mCurrentHidUsage;
        mCurrentHidUsage = 0;

        if (isKeyboardOrGamepadKey(scanCode)) {
            int32_t keyCode;
            //获取所对应的KeyCode【见小节3.4.2】
            if (getEventHub()->mapKey(getDeviceId(), scanCode, usageCode, &keyCode, &flags)) {
                keyCode = AKEYCODE_UNKNOWN;
                flags = 0;
            }
            //【见小节3.4.4】
            processKey(rawEvent->when, rawEvent->value != 0, keyCode, scanCode, flags);
        }
        break;
    }
    case EV_MSC: ...
    case EV_SYN: ...
    }
}

3.4.2 EventHub::mapKey

[-> EventHub.cpp]

status_t EventHub::mapKey(int32_t deviceId,
        int32_t scanCode, int32_t usageCode, int32_t metaState,
        int32_t* outKeycode, int32_t* outMetaState, uint32_t* outFlags) const {
    AutoMutex _l(mLock);
    Device* device = getDeviceLocked(deviceId); //获取设备对象
    status_t status = NAME_NOT_FOUND;

    if (device) {
        sp<KeyCharacterMap> kcm = device->getKeyCharacterMap();
        if (kcm != NULL) {
            //根据scanCode找到keyCode【见小节3.4.3】
            if (!kcm->mapKey(scanCode, usageCode, outKeycode)) {
                *outFlags = 0;
                status = NO_ERROR;
            }
        }
    }
    ...
    return status;
}

将事件的扫描码(scanCode)转换成键盘码(Keycode)

3.4.3 KeyCharacterMap::mapKey

[-> KeyCharacterMap.cpp]

status_t KeyCharacterMap::mapKey(int32_t scanCode, int32_t usageCode, int32_t* outKeyCode) const {
    ...
    if (scanCode) {
        ssize_t index = mKeysByScanCode.indexOfKey(scanCode);
        if (index >= 0) {
            //根据scanCode找到keyCode
            *outKeyCode = mKeysByScanCode.valueAt(index);
            return OK;
        }
    }
    *outKeyCode = AKEYCODE_UNKNOWN;
    return NAME_NOT_FOUND;
}

再回到[3.4.1],接下来进入如下过程:

3.4.4 InputMapper.processKey

[-> InputReader.cpp]

void KeyboardInputMapper::processKey(nsecs_t when, bool down, int32_t keyCode,
        int32_t scanCode, uint32_t policyFlags) {

    if (down) {
        if (mParameters.orientationAware && mParameters.hasAssociatedDisplay) {
            keyCode = rotateKeyCode(keyCode, mOrientation);
        }

        ssize_t keyDownIndex = findKeyDown(scanCode);
        if (keyDownIndex >= 0) {
            //mKeyDowns记录着所有按下的键
            keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;
        } else {
            ...
            mKeyDowns.push(); //压入栈顶
            KeyDown& keyDown = mKeyDowns.editTop();
            keyDown.keyCode = keyCode;
            keyDown.scanCode = scanCode;
        }
        mDownTime = when; //记录按下时间点

    } else {
        ssize_t keyDownIndex = findKeyDown(scanCode);
        if (keyDownIndex >= 0) {
            //键抬起操作,则移除按下事件
            keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;
            mKeyDowns.removeAt(size_t(keyDownIndex));
        } else {
            return;  //键盘没有按下操作,则直接忽略抬起操作
        }
    }
    nsecs_t downTime = mDownTime;
    ...

    //创建NotifyKeyArgs对象, when记录eventTime, downTime记录按下时间;
    NotifyKeyArgs args(when, getDeviceId(), mSource, policyFlags,
            down ? AKEY_EVENT_ACTION_DOWN : AKEY_EVENT_ACTION_UP,
            AKEY_EVENT_FLAG_FROM_SYSTEM, keyCode, scanCode, newMetaState, downTime);
    //通知key事件【见小节3.4.5】
    getListener()->notifyKey(&args);
}

参数说明:

  • mKeyDowns记录着所有按下的键;
  • mDownTime记录按下时间点;
  • 此处KeyboardInputMapper的mContext指向InputReader,getListener()获取的便是mQueuedListener。 接下来调用该对象的notifyKey.

3.4.5 QueuedInputListener.notifyKey

[-> InputListener.cpp]

void QueuedInputListener::notifyKey(const NotifyKeyArgs* args) {
    mArgsQueue.push(new NotifyKeyArgs(*args));
}

mArgsQueue的数据类型为Vector<NotifyArgs*>,将该key事件压人该栈顶。 到此,整个事件加工完成, 再然后就是将事件发送给InputDispatcher线程.

四. QueuedListener

4.1 QueuedInputListener.flush

[-> InputListener.cpp]

void QueuedInputListener::flush() {
    size_t count = mArgsQueue.size();
    for (size_t i = 0; i < count; i++) {
        NotifyArgs* args = mArgsQueue[i];
        //【见小节4.2】
        args->notify(mInnerListener);
        delete args;
    }
    mArgsQueue.clear();
}

从InputManager对象初始化的过程可知,mInnerListener便是InputDispatcher对象。

4.2 NotifyKeyArgs.notify

[-> InputListener.cpp]

void NotifyKeyArgs::notify(const sp<InputListenerInterface>& listener) const {
    listener->notifyKey(this); // this是指NotifyKeyArgs【见小节4.3】
}

4.3 InputDispatcher.notifyKey

[-> InputDispatcher.cpp]

void InputDispatcher::notifyKey(const NotifyKeyArgs* args) {
    if (!validateKeyEvent(args->action)) {
        return;
    }
    ...
    int32_t keyCode = args->keyCode;

    if (keyCode == AKEYCODE_HOME) {
        if (args->action == AKEY_EVENT_ACTION_DOWN) {
            property_set("sys.domekey.down", "1");
        } else if (args->action == AKEY_EVENT_ACTION_UP) {
            property_set("sys.domekey.down", "0");
        }
    }

    if (metaState & AMETA_META_ON && args->action == AKEY_EVENT_ACTION_DOWN) {
        ...
    } else if (args->action == AKEY_EVENT_ACTION_UP) {
        ...
    }

    KeyEvent event; //初始化KeyEvent对象
    event.initialize(args->deviceId, args->source, args->action,
            flags, keyCode, args->scanCode, metaState, 0,
            args->downTime, args->eventTime);
    //mPolicy是指NativeInputManager对象。【小节4.3.1】
    mPolicy->interceptKeyBeforeQueueing(&event, /*byref*/ policyFlags);

    bool needWake;
    {
        mLock.lock();
        if (shouldSendKeyToInputFilterLocked(args)) {
            mLock.unlock();
            policyFlags |= POLICY_FLAG_FILTERED;
            //当inputEventObj不为空, 则事件被filter所拦截【见小节4.3.2】
            if (!mPolicy->filterInputEvent(&event, policyFlags)) {
                return;
            }
            mLock.lock();
        }

        int32_t repeatCount = 0;
        //创建KeyEntry对象
        KeyEntry* newEntry = new KeyEntry(args->eventTime,
                args->deviceId, args->source, policyFlags,
                args->action, flags, keyCode, args->scanCode,
                metaState, repeatCount, args->downTime);
        //将KeyEntry放入队列【见小节4.3.3】
        needWake = enqueueInboundEventLocked(newEntry);
        mLock.unlock();
    }

    if (needWake) {
        //唤醒InputDispatcher线程【见小节4.3.5】
        mLooper->wake();
    }
}

该方法的主要功能:

  1. 调用NativeInputManager.interceptKeyBeforeQueueing,加入队列前执行拦截动作,但并不改变流程,调用链:
    • IMS.interceptKeyBeforeQueueing
    • InputMonitor.interceptKeyBeforeQueueing (继承IMS.WindowManagerCallbacks)
    • PhoneWindowManager.interceptKeyBeforeQueueing (继承WindowManagerPolicy)
  2. 当mInputFilterEnabled=true(该值默认为false,可通过setInputFilterEnabled设置),则调用NativeInputManager.filterInputEvent过滤输入事件;
    • 当返回值为false则过滤该事件,不再往下分发;
  3. 生成KeyEvent,并调用enqueueInboundEventLocked,将该事件加入到InputDispatcherd的成员变量mInboundQueue。

4.3.1 interceptKeyBeforeQueueing

void NativeInputManager::interceptKeyBeforeQueueing(const KeyEvent* keyEvent,
        uint32_t& policyFlags) {
    ...
    if ((policyFlags & POLICY_FLAG_TRUSTED)) {
        nsecs_t when = keyEvent->getEventTime(); //时间
        JNIEnv* env = jniEnv();
        jobject keyEventObj = android_view_KeyEvent_fromNative(env, keyEvent);
        if (keyEventObj) {
            // 调用Java层的IMS.interceptKeyBeforeQueueing
            wmActions = env->CallIntMethod(mServiceObj,
                    gServiceClassInfo.interceptKeyBeforeQueueing,
                    keyEventObj, policyFlags);
            ...
        } else {
            ...
        }
        handleInterceptActions(wmActions, when, /*byref*/ policyFlags);
    } else {
        ...
    }
}

该方法会调用Java层的InputManagerService的interceptKeyBeforeQueueing()方法。

4.3.2 filterInputEvent

bool NativeInputManager::filterInputEvent(const InputEvent* inputEvent, uint32_t policyFlags) {
    jobject inputEventObj;

    JNIEnv* env = jniEnv();
    switch (inputEvent->getType()) {
    case AINPUT_EVENT_TYPE_KEY:
        inputEventObj = android_view_KeyEvent_fromNative(env,
                static_cast<const KeyEvent*>(inputEvent));
        break;
    case AINPUT_EVENT_TYPE_MOTION:
        inputEventObj = android_view_MotionEvent_obtainAsCopy(env,
                static_cast<const MotionEvent*>(inputEvent));
        break;
    default:
        return true; // 走事件正常的分发流程
    }

    if (!inputEventObj) {
        return true; // 当inputEventObj为空, 则走事件正常的分发流程
    }

    //当inputEventObj不为空,则调用Java层的IMS.filterInputEvent()
    jboolean pass = env->CallBooleanMethod(mServiceObj, gServiceClassInfo.filterInputEvent,
            inputEventObj, policyFlags);
    if (checkAndClearExceptionFromCallback(env, "filterInputEvent")) {
        pass = true; //出现Exception,则走事件正常的分发流程
    }
    env->DeleteLocalRef(inputEventObj);
    return pass;
}

当inputEventObj不为空,则调用Java层的IMS.filterInputEvent(). 经过层层调用后, 最终会再调用InputDispatcher.injectInputEvent(),该基本等效于该方法的后半段:

  • enqueueInboundEventLocked
  • wakeup

4.3.3 enqueueInboundEventLocked

bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) {
    bool needWake = mInboundQueue.isEmpty();
    mInboundQueue.enqueueAtTail(entry); //将该事件放入mInboundQueue队列尾部

    switch (entry->type) {
    case EventEntry::TYPE_KEY: {
        KeyEntry* keyEntry = static_cast<KeyEntry*>(entry);
        if (isAppSwitchKeyEventLocked(keyEntry)) {
            if (keyEntry->action == AKEY_EVENT_ACTION_DOWN) {
                mAppSwitchSawKeyDown = true; //按下事件
            } else if (keyEntry->action == AKEY_EVENT_ACTION_UP) {
                if (mAppSwitchSawKeyDown) {
                    //其中APP_SWITCH_TIMEOUT=500ms
                    mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;
                    mAppSwitchSawKeyDown = false;
                    needWake = true;
                }
            }
        }
        break;
    }

    case EventEntry::TYPE_MOTION: {
        //当前App无响应且用户希望切换到其他应用窗口,则drop该窗口事件,并处理其他窗口事件
        MotionEntry* motionEntry = static_cast<MotionEntry*>(entry);
        if (motionEntry->action == AMOTION_EVENT_ACTION_DOWN
                && (motionEntry->source & AINPUT_SOURCE_CLASS_POINTER)
                && mInputTargetWaitCause == INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY
                && mInputTargetWaitApplicationHandle != NULL) {
            int32_t displayId = motionEntry->displayId;
            int32_t x = int32_t(motionEntry->pointerCoords[0].
                    getAxisValue(AMOTION_EVENT_AXIS_X));
            int32_t y = int32_t(motionEntry->pointerCoords[0].
                    getAxisValue(AMOTION_EVENT_AXIS_Y));
            //查询可触摸的窗口【见小节4.3.4】
            sp<InputWindowHandle> touchedWindowHandle = findTouchedWindowAtLocked(displayId, x, y);
            if (touchedWindowHandle != NULL
                    && touchedWindowHandle->inputApplicationHandle
                            != mInputTargetWaitApplicationHandle) {
                mNextUnblockedEvent = motionEntry;
                needWake = true;
            }
        }
        break;
    }
    }

    return needWake;
}

AppSwitchKeyEvent是指keyCode等于以下值:

  • AKEYCODE_HOME
  • AKEYCODE_ENDCALL
  • AKEYCODE_APP_SWITCH

4.3.4 findTouchedWindowAtLocked

[-> InputDispatcher.cpp]

sp<InputWindowHandle> InputDispatcher::findTouchedWindowAtLocked(int32_t displayId,
        int32_t x, int32_t y) {
    //从前台到后台来遍历查询可触摸的窗口
    size_t numWindows = mWindowHandles.size();
    for (size_t i = 0; i < numWindows; i++) {
        sp<InputWindowHandle> windowHandle = mWindowHandles.itemAt(i);
        const InputWindowInfo* windowInfo = windowHandle->getInfo();
        if (windowInfo->displayId == displayId) {
            int32_t flags = windowInfo->layoutParamsFlags;

            if (windowInfo->visible) {
                if (!(flags & InputWindowInfo::FLAG_NOT_TOUCHABLE)) {
                    bool isTouchModal = (flags & (InputWindowInfo::FLAG_NOT_FOCUSABLE
                            | InputWindowInfo::FLAG_NOT_TOUCH_MODAL)) == 0;
                    if (isTouchModal || windowInfo->touchableRegionContainsPoint(x, y)) {
                        return windowHandle; //找到目标窗口
                    }
                }
            }
        }
    }
    return NULL;
}

此处mWindowHandles的赋值过程是由Java层的InputMonitor.setInputWindows(),经过JNI调用后进入InputDispatcher::setInputWindows()方法完成. 进一步说, 就是WMS执行addWindow()过程或许UI改变等场景,都会触发该方法的修改.

4.3.5 Looper.wake

[-> system/core/libutils/Looper.cpp]

void Looper::wake() {
    uint64_t inc = 1;

    ssize_t nWrite = TEMP_FAILURE_RETRY(write(mWakeEventFd, &inc, sizeof(uint64_t)));
    if (nWrite != sizeof(uint64_t)) {
        if (errno != EAGAIN) {
            ALOGW("Could not write wake signal, errno=%d", errno);
        }
    }
}

[小节4.3]的过程会调用enqueueInboundEventLocked()方法来决定是否需要将数字1写入句柄mWakeEventFd来唤醒InputDispatcher线程. 满足唤醒的条件:

  1. 执行enqueueInboundEventLocked方法前,mInboundQueue队列为空,执行完必然不再为空,则需要唤醒分发线程;
  2. 当事件类型为key事件,且发生一对按下和抬起操作,则需要唤醒;
  3. 当事件类型为motion事件,且当前可触摸的窗口属于另一个应用,则需要唤醒.

五. 总结

5.1 核心工作

InputReader整个过程涉及多次事件封装转换,其主要工作核心是以下三大步骤:

  • getEvents:通过EventHub(监听目录/dev/input)读取事件放入mEventBuffer,而mEventBuffer是一个大小为256的数组, 再将事件input_event转换为RawEvent; [见小节2.1]
  • processEventsLocked: 对事件进行加工, 转换RawEvent -> NotifyKeyArgs(NotifyArgs) [见小节3.1]
  • QueuedListener->flush:将事件发送到InputDispatcher线程, 转换NotifyKeyArgs -> KeyEntry(EventEntry) [见小节4.1]

InputReader线程不断循环地执行InputReader.loopOnce(), 每次处理完生成的是EventEntry(比如KeyEntry, MotionEntry), 接下来的工作就交给InputDispatcher线程。

5.2 流程图

点击查看大图:

input_reader_seq

InputReader的核心工作就是从EventHub获取数据后生成EventEntry事件,加入到InputDispatcher的mInboundQueue队列,再唤醒InputDispatcher线程。

input_reader

说明:

  • IMS.filterInputEvent可以过滤无需上报的事件,当该方法返回值为false则代表是需要被过滤掉的事件,无机会交给InputDispatcher来分发。
  • 节点/dev/input的event事件所对应的输入设备信息位于/proc/bus/input/devices,也可以通过getevent来获取事件. 不同的input事件所对应的物理input节点,比如常见的情形:
    • 屏幕触摸和(MENU,HOME,BACK)3按键:对应同一个input设备节点;
    • POWER和音量(下)键:对应同一个input设备节点;
    • 音量(上)键:对应同一个input设备节点;

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