Android输入系统之InputChannel(上)

        前面的“锤子快捷键”相关文章已经分析了输入事件的读取，处理，分发。我们知道事件的传递是以window为单位传递的，即server只负责将事件传递给某一个或者多个window，window然后再将事件传递给某一个具体的view。一个activity或者dialog对应一个window，但是事件只传递给合适的window，比如对于按键事件，就必须是获得焦点的window,也就是说只能传递给一个window,通常是最上面的程序。找到了合适的window,然后就是将事件添加到window的Connection的事件队列上。其实，到这为止输入事件还只是在server端，即system_server这个进程里，要想让程序获取到事件，肯定必须将事件信息传递到程序端的进程里。这个就是Connection的实现问题了，这个connection的真正逻辑是InputChannel, InputChannel其实就是linux unix socket的一种封装, unixsocket是linux的一种跨进程通信方式。系统创建InputChannel对即unix socket对，系统server端和程序client各只有其中一个，这样通过unix socket就可以给对方发送消息，而这里的事件就是通过这种方式从系统进程传递到程序进程的。整个系统框架图如下：

系统server端的InputChannel

系统InputChannel的整个处理逻辑如下：

Server端 InputChannel的创建

         Server端 InputChannel是在window被创建的时候创建的：

    //addWindow会创建一个channel对，其实上就是unix socket对，其中一个unix socket
    //通过传入参数outInputChannel被传递到程序端,
    //另外一个unix socket保存在server的window中并注册到native的InputManager
    public int addWindow(Session session, IWindow client, int seq,
            WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
            Rect outContentInsets, InputChannel outInputChannel) {
            //创建window的数据对象WindowState
            win = new WindowState(this, session, client, token,
                    attachedWindow, appOp[0], seq, attrs, viewVisibility, displayContent);
            if (outInputChannel != null && (attrs.inputFeatures & 
                WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
                String name = win.makeInputChannelName();
                //创建channel对，即会返回两个InputChannel
                InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);
                //一个unix socket保存到window里
                win.setInputChannel(inputChannels[0]);
                //另外一个unix socket传递到程序端
                inputChannels[1].transferTo(outInputChannel);
                //这个函数很重要，这个会将server端的unix socket注册到native层
                //的InputManager,  win.mInputChannel就是上面的inputChannels[0]
                mInputManager.registerInputChannel(win.mInputChannel, 
                       win.mInputWindowHandle);
            }
        }
        return res;
}

public static InputChannel[] openInputChannelPair(String name) {
        return nativeOpenInputChannelPair(name);
}

static jobjectArray android_view_InputChannel_nativeOpenInputChannelPair(JNIEnv* env,
        jclass clazz, jstring nameObj) {
    sp serverChannel;
    sp clientChannel;
     //创建input channel对
    status_t result = InputChannel::openInputChannelPair(name, 
         serverChannel, clientChannel);
    jobjectArray channelPair = env->NewObjectArray(2, gInputChannelClassInfo.clazz, NULL);
    //创建inputChannel对应的java对象
    jobject serverChannelObj = android_view_InputChannel_createInputChannel(env,
            new NativeInputChannel(serverChannel));
    jobject clientChannelObj = android_view_InputChannel_createInputChannel(env,
            new NativeInputChannel(clientChannel));
    //将两个channel放到channel数组中
    env->SetObjectArrayElement(channelPair, 0, serverChannelObj);
    env->SetObjectArrayElement(channelPair, 1, clientChannelObj);
    return channelPair;
}
//InputTransport.cpp
status_t InputChannel::openInputChannelPair(const String8& name,
        sp& outServerChannel, sp& outClientChannel) {
    int sockets[2];
    //很早的android 版本是使用双向管道实现的，而是现在是使用unix socket双通道
    //来通信
    if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) {
        return result;
    }

    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));

    String8 serverChannelName = name;
    serverChannelName.append(" (server)");
    //创建InputChannel，并把通信文件句柄传入
    outServerChannel = new InputChannel(serverChannelName, sockets[0]);

    String8 clientChannelName = name;
    clientChannelName.append(" (client)");
    //创建InputChannel，并把通信文件句柄传入
    outClientChannel = new InputChannel(clientChannelName, sockets[1]);
    return OK;
}

Server端 InputChannel事件监听器安装

         InputDispatcher要能够发送事件数据，必须的要让其知道对应的window的InputChannel，这个通过注册实现的。

public void registerInputChannel(InputChannel inputChannel,
            InputWindowHandle inputWindowHandle) {        
        nativeRegisterInputChannel(mPtr, inputChannel, inputWindowHandle, false);
}

status_t NativeInputManager::registerInputChannel(JNIEnv* env,
        const sp& inputChannel,
        const sp& inputWindowHandle, bool monitor) {
    //调用InputDispatcher的函数
    return mInputManager->getDispatcher()->registerInputChannel(
            inputChannel, inputWindowHandle, monitor);
}

status_t InputDispatcher::registerInputChannel(const sp& inputChannel,
        const sp& inputWindowHandle, bool monitor) {
    { // acquire lock
        AutoMutex _l(mLock);
        //这个将inputChannel封装为Connection
        sp connection = new Connection(inputChannel, 
inputWindowHandle, monitor);
            //这个就是unix socket文件句柄
        int fd = inputChannel->getFd();
        //将connection保存到映射表中
        mConnectionsByFd.add(fd, connection);
        //监听该unix socket文件，当unix socket有数据时即client发送消息过来了，
        //函数handleReceiveCallback就会被执行
        mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, handleReceiveCallback, this);
    } // release lock

    // Wake the looper because some connections have changed.
    mLooper->wake();
    return OK;
}

Server端的InputChannel事件数据发送

    在上几篇文章“锤子快捷键配置”中，已经讲到了事件分发，并最后将事件放到了connection的事件队列中，InputChannel事件发送就是从开始的

void InputDispatcher::enqueueDispatchEntriesLocked(nsecs_t currentTime,
        const sp& connection, EventEntry* eventEntry, const InputTarget* inputTarget) {
    bool wasEmpty = connection->outboundQueue.isEmpty();
    // Enqueue dispatch entries for the requested modes.
    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,
            InputTarget::FLAG_DISPATCH_AS_HOVER_EXIT);
    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,
            InputTarget::FLAG_DISPATCH_AS_OUTSIDE);
    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,
            InputTarget::FLAG_DISPATCH_AS_HOVER_ENTER);
    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,
            InputTarget::FLAG_DISPATCH_AS_IS);
    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,
            InputTarget::FLAG_DISPATCH_AS_SLIPPERY_EXIT);
    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,
            InputTarget::FLAG_DISPATCH_AS_SLIPPERY_ENTER);

    // 原来是空，现在不空，则立刻分发事件
    if (wasEmpty && !connection->outboundQueue.isEmpty()) {
        startDispatchCycleLocked(currentTime, connection);
    }
} 

void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,
        const sp& connection) {
    //遍历所有发送队列中的事件
    while (connection->status == Connection::STATUS_NORMAL
            && !connection->outboundQueue.isEmpty()) {
        //获取最早的需要发送的事件
        DispatchEntry* dispatchEntry = connection->outboundQueue.head;
        EventEntry* eventEntry = dispatchEntry->eventEntry;
        switch (eventEntry->type) {
        case EventEntry::TYPE_KEY: {
            KeyEntry* keyEntry = static_cast(eventEntry);
            
            //真正发送事件.
            status = connection->inputPublisher.publishKeyEvent(dispatchEntry->seq,
                    keyEntry->deviceId, keyEntry->source,
                    dispatchEntry->resolvedAction, dispatchEntry->resolvedFlags,
                    keyEntry->keyCode, keyEntry->scanCode,
                    keyEntry->metaState, keyEntry->repeatCount, keyEntry->downTime,
                    keyEntry->eventTime);
            break;
        }

        // Check the result.
        if (status) {
            if (status == WOULD_BLOCK) {
                if (connection->waitQueue.isEmpty()) {
                } else {
                    connection->inputPublisherBlocked = true;
                }
            }
            //发送成功，返回执行下一次循环
            return;
        }

        // 事件发送失败，重新放进待发送队列
        connection->outboundQueue.dequeue(dispatchEntry);
        connection->waitQueue.enqueueAtTail(dispatchEntry);
    }
}

status_t InputPublisher::publishKeyEvent(
        uint32_t seq,
        int32_t deviceId,
        int32_t source,
        int32_t action,
        int32_t flags,
        int32_t keyCode,
        int32_t scanCode,
        int32_t metaState,
        int32_t repeatCount,
        nsecs_t downTime,
        nsecs_t eventTime) {
    InputMessage msg;
    //将输入事件转化为unix socket通信的格式
    msg.header.type = InputMessage::TYPE_KEY;
    msg.body.key.seq = seq;
    msg.body.key.deviceId = deviceId;
    msg.body.key.source = source;
    msg.body.key.action = action;
    msg.body.key.flags = flags;
    msg.body.key.keyCode = keyCode;
    msg.body.key.scanCode = scanCode;
    msg.body.key.metaState = metaState;
    msg.body.key.repeatCount = repeatCount;
    msg.body.key.downTime = downTime;
msg.body.key.eventTime = eventTime;
    //调用unix socket消息发送机制
    return mChannel->sendMessage(&msg);
}

status_t InputChannel::sendMessage(const InputMessage* msg) {
    size_t msgLength = msg->size();
    ssize_t nWrite;
do {
    //通过unix socket将事件数据发送到程序端
        nWrite = ::send(mFd, msg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL);
    } while (nWrite == -1 && errno == EINTR);
    return OK;
}

程序client端的InputChannel

client的InputChannel相关的处理逻辑如下：

 Client 端的InputChannel创建

         Client接受事件，肯定必须先获得inputChannel，这个是在addWindow时系统返回回来的。

         

public void setView(View view, WindowManager.LayoutParams attrs, 
View panelParentView) {
        synchronized (this) {
                if ((mWindowAttributes.inputFeatures&
                   WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
                    mInputChannel = new InputChannel();
                }
                try {
                    //该函数会返回一个InputChannel
                    res = mWindowSession.addToDisplay(mWindow, mSeq,
                            mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(),
                            mAttachInfo.mContentInsets, mInputChannel);
                }
                if (mInputChannel != null) {
                    if (mInputQueueCallback != null) {
                        mInputQueue = new InputQueue();
                        mInputQueueCallback.onInputQueueCreated(mInputQueue);
                    }
                    //为InputChannel注册监听器
                    mInputEventReceiver = new WindowInputEventReceiver(
                         mInputChannel,
                         Looper.myLooper());
                }
          }
} 
  
 
  
 
  
 
  
Client端的 InputChannel监听器安装
 
  
         InputChannel监听器安装在WindowInputEventReceiver初始化的时候
 
  
         
 
  
final class WindowInputEventReceiver extends InputEventReceiver {
        public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
            super(inputChannel, looper);
        }
}
public InputEventReceiver(InputChannel inputChannel, Looper looper) {
        mInputChannel = inputChannel;
        mMessageQueue = looper.getQueue();
        mReceiverPtr = nativeInit(new WeakReference(this),
                inputChannel, mMessageQueue);

        mCloseGuard.open("dispose");
 }

static jint nativeInit(JNIEnv* env, jclass clazz, jobject receiverWeak,
        jobject inputChannelObj, jobject messageQueueObj) {
    //获取native层的InputChannel
    sp inputChannel = android_view_InputChannel_getInputChannel(env,
            inputChannelObj);
    //获取java层InputEventReceiver对象的native层的消息队列
    sp messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);
        //创建native对应的InputEventReceiver对象
    sp receiver = new NativeInputEventReceiver(env,
            receiverWeak, inputChannel, messageQueue);
    //这个是真正安装监听的函数
    status_t status = receiver->initialize();
    return reinterpret_cast(receiver.get());
}


status_t NativeInputEventReceiver::initialize() {
    //安装监听器
    setFdEvents(ALOOPER_EVENT_INPUT);
    return OK;
}

void NativeInputEventReceiver::setFdEvents(int events) {
    if (mFdEvents != events) {
        mFdEvents = events;
        int fd = mInputConsumer.getChannel()->getFd();
        if (events) {
           //用looper监听inputChannel对应的unix socket文件句柄
            mMessageQueue->getLooper()->addFd(fd, 0, events, this, NULL);
        }
    }
}

int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, void* data) {
    return addFd(fd, ident, events, callback ? new SimpleLooperCallback(callback) : NULL, data);
}

int Looper::addFd(int fd, int ident, int events, const sp& callback, void* data) {
    { // acquire lock
        AutoMutex _l(mLock);
        //将监听参数封装
        Request request;
        request.fd = fd;
        request.ident = ident;
        //这个很重要，当被监听的文件发生变化时就会调用该callback函数
        request.callback = callback;
        request.data = data;

        ssize_t requestIndex = mRequests.indexOfKey(fd);
        if (requestIndex < 0) {
            //epoll该文件，也就是讲unix socket文件添加到监听文件列表中
            int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);
            mRequests.add(fd, request);
        }
    } // release lock
    return 1;
}

 
  
 
  
 
  
Client端的InputChannel中的事件接收
 
  
         从上面可以看出，Java的InputEventReceiver层的native层的NativeInputEventReceiver负责监听事件，当有事件时，就会调用它。
 
  
           
 
  
int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
    int result = 0;
    for (;;) {
        while (mResponseIndex < mResponses.size()) {
            const Response& response = mResponses.itemAt(mResponseIndex++);
            int ident = response.request.ident;
            if (ident >= 0) {
                int fd = response.request.fd;
                int events = response.events;
                void* data = response.request.data;
                if (outFd != NULL) *outFd = fd;
                if (outEvents != NULL) *outEvents = events;
                if (outData != NULL) *outData = data;
                return ident;
            }
        }
        result = pollInner(timeoutMillis);
    }
}

int Looper::pollInner(int timeoutMillis) {
    struct epoll_event eventItems[EPOLL_MAX_EVENTS];
    //等待消息
    int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);
    for (int i = 0; i < eventCount; i++) {
        int fd = eventItems[i].data.fd;
        uint32_t epollEvents = eventItems[i].events;
        if (fd == mWakeReadPipeFd) {
            if (epollEvents & EPOLLIN) {
                awoken();
            }
        } else {
            ssize_t requestIndex = mRequests.indexOfKey(fd);
            if (requestIndex >= 0) {
                int events = 0;
                if (epollEvents & EPOLLIN) events |= ALOOPER_EVENT_INPUT;
                if (epollEvents & EPOLLOUT) events |= ALOOPER_EVENT_OUTPUT;
                if (epollEvents & EPOLLERR) events |= ALOOPER_EVENT_ERROR;
                if (epollEvents & EPOLLHUP) events |= ALOOPER_EVENT_HANGUP;
                //将事件放到事件队列上
                pushResponse(events, mRequests.valueAt(requestIndex));
            }
        }
    }
Done: ;
    //处理前面加入的response事件
    for (size_t i = 0; i < mResponses.size(); i++) {
        Response& response = mResponses.editItemAt(i);
        if (response.request.ident == ALOOPER_POLL_CALLBACK) {
            int fd = response.request.fd;
            int events = response.events;
            void* data = response.request.data;
            // 下面的callback就是 NativeInputEventRecieverd
            int callbackResult = response.request.callback->handleEvent(fd, events, data);
            if (callbackResult == 0) {
                removeFd(fd);
            }
            response.request.callback.clear();
            result = ALOOPER_POLL_CALLBACK;
        }
    }
    return result;
}


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, NULL);
        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) {
    for (;;) {
        uint32_t seq;
        InputEvent* inputEvent;
        //从buffer中还原出事件
        status_t status = mInputConsumer.consume(&mInputEventFactory,
                consumeBatches, frameTime, &seq, &inputEvent);
        if (!skipCallbacks) {
            jobject inputEventObj;
            switch (inputEvent->getType()) {
            case AINPUT_EVENT_TYPE_KEY:
                //转换为java层的InputEvent
                inputEventObj = android_view_KeyEvent_fromNative(env,
                        static_cast(inputEvent));
                break;
            }
            if (inputEventObj) {
                //这个就会调用到java层的函数InputEventReceiver->dispatchInputEvent
                env->CallVoidMethod(receiverObj.get(),
                        gInputEventReceiverClassInfo.dispatchInputEvent, seq,
 inputEventObj);
            }
        }
    }
}

 
               
  
 
  
Client端对输入事件的处理
 
  
 
  
          到此为止，事件开始传递到了JAVA层了，然后就是JAVA层开始对事件进行处理，我们通常接触的事件处理也是在java层实现的，这个将在下一篇介绍。
 
  

 
  
 
  
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