Android10 输入输出系统InputDispatcher线程分析

一. InputDispatcher起点

上篇文章我们介绍InputReader利用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。本文将介绍InputDispatcher，同样从threadLoop为起点开始分析。

1.1 threadLoop

先来回顾一下InputDispatcher对象的初始化过程:

InputDispatcher::InputDispatcher(const sp<InputDispatcherPolicyInterface>& policy) :
    mPolicy(policy),
    mPendingEvent(NULL), mLastDropReason(DROP_REASON_NOT_DROPPED),
    mAppSwitchSawKeyDown(false), mAppSwitchDueTime(LONG_LONG_MAX),
    mNextUnblockedEvent(NULL),
    mDispatchEnabled(false), mDispatchFrozen(false), mInputFilterEnabled(false),
    mInputTargetWaitCause(INPUT_TARGET_WAIT_CAUSE_NONE) {
    //创建Looper对象
    mLooper = new Looper(false);

    mKeyRepeatState.lastKeyEntry = NULL;
    //获取分发超时参数
    policy->getDispatcherConfiguration(&mConfig);
}

该方法主要工作：

创建属于自己线程的Looper对象；
超时参数来自于IMS，参数默认值keyRepeatTimeout = 500，keyRepeatDelay = 50。

[-> InputDispatcher.cpp]

bool InputDispatcherThread::threadLoop() {
    mDispatcher->dispatchOnce(); //【见小节1.2】
    return true;
}

整个过程不断循环地调用InputDispatcher的dispatchOnce()来分发事件

1.2 dispatchOnce

[-> InputDispatcher.cpp]

void InputDispatcher::dispatchOnce() {
    nsecs_t nextWakeupTime = LONG_LONG_MAX;
    {
        AutoMutex _l(mLock);
        //唤醒等待线程，monitor()用于监控dispatcher是否发生死锁
        mDispatcherIsAliveCondition.broadcast();

        if (!haveCommandsLocked()) {
            //当mCommandQueue不为空时处理【见小节2.1】
            dispatchOnceInnerLocked(&nextWakeupTime);
        }

        //【见小节3.1】
        if (runCommandsLockedInterruptible()) {
            nextWakeupTime = LONG_LONG_MIN;
        }
    }

    nsecs_t currentTime = now();
    int timeoutMillis = toMillisecondTimeoutDelay(currentTime, nextWakeupTime);
    mLooper->pollOnce(timeoutMillis); //进入epoll_wait
}

线程执行Looper->pollOnce，进入epoll_wait等待状态，当发生以下任一情况则退出等待状态：

callback：通过回调方法来唤醒；
timeout：到达nextWakeupTime时间，超时唤醒；
wake: 主动调用Looper的wake()方法；

二. InputDispatcher

2.1 dispatchOnceInnerLocked

void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) {
    nsecs_t currentTime = now(); //当前时间，也是后面ANR计时的起点

    if (!mDispatchEnabled) { //默认值为false
        resetKeyRepeatLocked(); //重置操作
    }
    if (mDispatchFrozen) { //默认值为false
        return; //当分发被冻结，则不再处理超时和分发事件的工作，直接返回
    }

    //优化app切换延迟，当切换超时，则抢占分发，丢弃其他所有即将要处理的事件。
    bool isAppSwitchDue = mAppSwitchDueTime <= currentTime;
    ...

    if (!mPendingEvent) {
        if (mInboundQueue.isEmpty()) {
            if (!mPendingEvent) {
                return; //没有事件需要处理，则直接返回
            }
        } else {
            //从mInboundQueue取出头部的事件
            mPendingEvent = mInboundQueue.dequeueAtHead();
        }
        ...
        resetANRTimeoutsLocked(); //重置ANR信息[见小节2.1.1]
    }

    bool done = false;
    DropReason dropReason = DROP_REASON_NOT_DROPPED;
    if (!(mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER)) {
        dropReason = DROP_REASON_POLICY;
    } else if (!mDispatchEnabled) {
        dropReason = DROP_REASON_DISABLED;
    }
    ...

    switch (mPendingEvent->type) {
      case EventEntry::TYPE_KEY: {
          KeyEntry* typedEntry = static_cast<KeyEntry*>(mPendingEvent);
          if (isAppSwitchDue) {
              if (isAppSwitchKeyEventLocked(typedEntry)) {
                  resetPendingAppSwitchLocked(true);
                  isAppSwitchDue = false;
              } else if (dropReason == DROP_REASON_NOT_DROPPED) {
                  dropReason = DROP_REASON_APP_SWITCH;
              }
          }
          if (dropReason == DROP_REASON_NOT_DROPPED
                  && isStaleEventLocked(currentTime, typedEntry)) {
              dropReason = DROP_REASON_STALE;
          }
          if (dropReason == DROP_REASON_NOT_DROPPED && mNextUnblockedEvent) {
              dropReason = DROP_REASON_BLOCKED;
          }
          // 分发按键事件[见小节2.2]
          done = dispatchKeyLocked(currentTime, typedEntry, &dropReason, nextWakeupTime);
          break;
      }
      ...
    }
    ...

    //分发操作完成，则进入该分支
    if (done) {
        if (dropReason != DROP_REASON_NOT_DROPPED) {
            //[见小节2.1.2]
            dropInboundEventLocked(mPendingEvent, dropReason);
        }
        mLastDropReason = dropReason;
        releasePendingEventLocked(); //释放pending事件见小节2.10]
        *nextWakeupTime = LONG_LONG_MIN; //强制立刻执行轮询
    }
}

在enqueueInboundEventLocked()的过程中已设置mAppSwitchDueTime等于eventTime加上500ms:

mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;

该方法主要功能:

mDispatchFrozen用于决定是否冻结事件分发工作不再往下执行;
当事件分发的时间点距离该事件加入mInboundQueue的时间超过500ms,则认为app切换过期,即isAppSwitchDue=true;
mInboundQueue不为空,则取出头部的事件,放入mPendingEvent变量;并重置ANR时间;
根据EventEntry的type类型分别处理，比如按键调用dispatchKeyLocked分发事件;再根据分发结果来决定是否进入done;
执行完成(done)的处理:
- 根据dropReason(默认NOT_DROPPED不处理)来决定是否丢失事件; dropInboundEventLocked
- 释放当前正在处理的事件(即mPendingEvent)； releasePendingEventLocked

关于dispatchKeyLocked分发事件,

不会执行done过情况:
- 当前Event时间小于唤醒时间;
- 让policy有机会执行拦截操作;
- 调用findFocusedWindowTargetsLocked方法的返回结果是INPUT_EVENT_INJECTION_PENDING, 即targets没有处于Ready状态;
会执行done的情况:
- 该事件需要丢弃, 即dropReason != DROP_REASON_NOT_DROPPED;
- findFocusedWindowTargetsLocked的返回结果不是INPUT_EVENT_INJECTION_PENDING(没有正在处理的事件);

接下来以按键为例来展开说明, 则进入[小节2.2] dispatchKeyLocked.

2.1.1 resetANRTimeoutsLocked

void InputDispatcher::resetANRTimeoutsLocked() {
    // 重置等待超时cause和handle
    mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_NONE;
    mInputTargetWaitApplicationHandle.clear();
}

2.1.2 dropInboundEventLocked

void InputDispatcher::dropInboundEventLocked(EventEntry* entry, DropReason dropReason) {
    const char* reason;
    switch (dropReason) {
    case DROP_REASON_POLICY:
        reason = "inbound event was dropped because the policy consumed it";
        break;
    case DROP_REASON_DISABLED:
        if (mLastDropReason != DROP_REASON_DISABLED) {
            ALOGI("Dropped event because input dispatch is disabled.");
        }
        reason = "inbound event was dropped because input dispatch is disabled";
        break;
    case DROP_REASON_APP_SWITCH:
        ALOGI("Dropped event because of pending overdue app switch.");
        reason = "inbound event was dropped because of pending overdue app switch";
        break;
    case DROP_REASON_BLOCKED:
        ALOGI("Dropped event because the current application is not responding and the user "
                "has started interacting with a different application.");
        reason = "inbound event was dropped because the current application is not responding "
                "and the user has started interacting with a different application";
        break;
    case DROP_REASON_STALE:
        ALOGI("Dropped event because it is stale.");
        reason = "inbound event was dropped because it is stale";
        break;
    default:
        return;
    }

    switch (entry->type) {
    case EventEntry::TYPE_KEY: {
        CancelationOptions options(CancelationOptions::CANCEL_NON_POINTER_EVENTS, reason);
        synthesizeCancelationEventsForAllConnectionsLocked(options);
        break;
    }
    ...
    }
}

2.2 dispatchKeyLocked

bool InputDispatcher::dispatchKeyLocked(nsecs_t currentTime, KeyEntry* entry,
        DropReason* dropReason, nsecs_t* nextWakeupTime) {
    ...
    if (entry->interceptKeyResult == KeyEntry::INTERCEPT_KEY_RESULT_TRY_AGAIN_LATER) {
        // case1: 当前时间小于唤醒时间，则进入等待状态。
        if (currentTime < entry->interceptKeyWakeupTime) {
            if (entry->interceptKeyWakeupTime < *nextWakeupTime) {
                *nextWakeupTime = entry->interceptKeyWakeupTime;
            }
            return false; //直接返回
        }
        entry->interceptKeyResult = KeyEntry::INTERCEPT_KEY_RESULT_UNKNOWN;
        entry->interceptKeyWakeupTime = 0;
    }

    if (entry->interceptKeyResult == KeyEntry::INTERCEPT_KEY_RESULT_UNKNOWN) {
        //case2: 让policy有机会执行拦截操作
        if (entry->policyFlags & POLICY_FLAG_PASS_TO_USER) {
            CommandEntry* commandEntry = postCommandLocked(
                    & InputDispatcher::doInterceptKeyBeforeDispatchingLockedInterruptible);
            if (mFocusedWindowHandle != NULL) {
                commandEntry->inputWindowHandle = mFocusedWindowHandle;
            }
            commandEntry->keyEntry = entry;
            entry->refCount += 1;
            return false; //直接返回
        } else {
            entry->interceptKeyResult = KeyEntry::INTERCEPT_KEY_RESULT_CONTINUE;
        }
    } else if (entry->interceptKeyResult == KeyEntry::INTERCEPT_KEY_RESULT_SKIP) {
        if (*dropReason == DROP_REASON_NOT_DROPPED) {
            *dropReason = DROP_REASON_POLICY;
        }
    }

    //case3: 如果需要丢弃该事件，则执行清理操作
    if (*dropReason != DROP_REASON_NOT_DROPPED) {
        setInjectionResultLocked(entry, *dropReason == DROP_REASON_POLICY
                ? INPUT_EVENT_INJECTION_SUCCEEDED : INPUT_EVENT_INJECTION_FAILED);
        return true; //直接返回
    }

    Vector<InputTarget> inputTargets;
    //case4: 寻找焦点 【见小节2.3】
    int32_t injectionResult = findFocusedWindowTargetsLocked(currentTime,
            entry, inputTargets, nextWakeupTime);
    if (injectionResult == INPUT_EVENT_INJECTION_PENDING) {
        return false; //直接返回
    }

    setInjectionResultLocked(entry, injectionResult);
    if (injectionResult != INPUT_EVENT_INJECTION_SUCCEEDED) {
        return true; //直接返回
    }
    addMonitoringTargetsLocked(inputTargets);

    //只有injectionResult是成功，才有机会执行分发事件【见小节2.4】
    dispatchEventLocked(currentTime, entry, inputTargets);
    return true;
}

在以下场景下，有可能无法分发事件：

当前时间小于唤醒时间(nextWakeupTime)的情况；
policy需要提前拦截事件的情况；
需要drop事件的情况；
寻找聚焦窗口失败的情况；

如果成功跳过以上所有情况，则会进入执行事件分发的过程。

2.3 findFocusedWindowTargetsLocked

int32_t InputDispatcher::findFocusedWindowTargetsLocked(nsecs_t currentTime,
        const EventEntry* entry, Vector<InputTarget>& inputTargets, nsecs_t* nextWakeupTime) {
    int32_t injectionResult;
    String8 reason;

    if (mFocusedWindowHandle == NULL) {
        if (mFocusedApplicationHandle != NULL) {
            //【见小节2.3.2】
            injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                    mFocusedApplicationHandle, NULL, nextWakeupTime,
                    "Waiting because no window has focus but there is a "
                    "focused application that may eventually add a window "
                    "when it finishes starting up.");
            goto Unresponsive;
        }

        ALOGI("Dropping event because there is no focused window or focused application.");
        injectionResult = INPUT_EVENT_INJECTION_FAILED;
        goto Failed;
    }

    //权限检查
    if (! checkInjectionPermission(mFocusedWindowHandle, entry->injectionState)) {
        injectionResult = INPUT_EVENT_INJECTION_PERMISSION_DENIED;
        goto Failed;
    }

    //检测窗口是否为更多的输入操作而准备就绪【见小节2.3.1】
    reason = checkWindowReadyForMoreInputLocked(currentTime,
            mFocusedWindowHandle, entry, "focused");
    if (!reason.isEmpty()) {
        //【见小节2.3.2】
        injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                mFocusedApplicationHandle, mFocusedWindowHandle, nextWakeupTime, reason.string());
        goto Unresponsive;
    }

    injectionResult = INPUT_EVENT_INJECTION_SUCCEEDED;
    //成功找到目标窗口，添加到目标窗口 [见小节2.3.3]
    addWindowTargetLocked(mFocusedWindowHandle,
            InputTarget::FLAG_FOREGROUND | InputTarget::FLAG_DISPATCH_AS_IS, BitSet32(0),
            inputTargets);

Failed:
Unresponsive:
    //TODO: 统计等待时长信息，目前没有实现，这个方法还是很值得去改造
    nsecs_t timeSpentWaitingForApplication = getTimeSpentWaitingForApplicationLocked(currentTime);
    updateDispatchStatisticsLocked(currentTime, entry,
          injectionResult, timeSpentWaitingForApplication);
    return injectionResult;
}

此处mFocusedWindowHandle是何处赋值呢？是在InputDispatcher.setInputWindows()方法.

寻找聚焦窗口失败的情况：

无窗口，无应用：Dropping event because there is no focused window or focused application.(这并不导致ANR的情况，因为没有机会调用handleTargetsNotReadyLocked)
无窗口, 有应用：Waiting because no window has focus but there is a focused application that may eventually add a window when it finishes starting up.

另外，还有更多的失败场景见checkWindowReadyForMoreInputLocked的过程，如下：

2.3.1 checkWindowReadyForMoreInputLocked

String8 InputDispatcher::checkWindowReadyForMoreInputLocked(nsecs_t currentTime,
        const sp<InputWindowHandle>& windowHandle, const EventEntry* eventEntry,
        const char* targetType) {
    //当窗口暂停的情况，则保持等待
    if (windowHandle->getInfo()->paused) {
        return String8::format("Waiting because the %s window is paused.", targetType);
    }

    //当窗口连接未注册，则保持等待
    ssize_t connectionIndex = getConnectionIndexLocked(windowHandle->getInputChannel());
    if (connectionIndex < 0) {
        return String8::format("Waiting because the %s window's input channel is not "
                "registered with the input dispatcher.  The window may be in the process "
                "of being removed.", targetType);
    }

    //当窗口连接已死亡，则保持等待
    sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);
    if (connection->status != Connection::STATUS_NORMAL) {
        return String8::format("Waiting because the %s window's input connection is %s."
                "The window may be in the process of being removed.", targetType,
                connection->getStatusLabel());
    }

    // 当窗口连接已满，则保持等待
    if (connection->inputPublisherBlocked) {
        return String8::format("Waiting because the %s window's input channel is full.  "
                "Outbound queue length: %d.  Wait queue length: %d.",
                targetType, connection->outboundQueue.count(), connection->waitQueue.count());
    }


    if (eventEntry->type == EventEntry::TYPE_KEY) {
        // 按键事件，输出队列或事件等待队列不为空
        if (!connection->outboundQueue.isEmpty() || !connection->waitQueue.isEmpty()) {
            return String8::format("Waiting to send key event because the %s window has not "
                    "finished processing all of the input events that were previously "
                    "delivered to it.  Outbound queue length: %d.  Wait queue length: %d.",
                    targetType, connection->outboundQueue.count(), connection->waitQueue.count());
        }
    } else {
        // 非按键事件，事件等待队列不为空且头事件分发超时500ms
        if (!connection->waitQueue.isEmpty()
                && currentTime >= connection->waitQueue.head->deliveryTime
                        + STREAM_AHEAD_EVENT_TIMEOUT) {
            return String8::format("Waiting to send non-key event because the %s window has not "
                    "finished processing certain input events that were delivered to it over "
                    "%0.1fms ago.  Wait queue length: %d.  Wait queue head age: %0.1fms.",
                    targetType, STREAM_AHEAD_EVENT_TIMEOUT * 0.000001f,
                    connection->waitQueue.count(),
                    (currentTime - connection->waitQueue.head->deliveryTime) * 0.000001f);
        }
    }
    return String8::empty();
}

2.3.2 handleTargetsNotReadyLocked

int32_t InputDispatcher::handleTargetsNotReadyLocked(nsecs_t currentTime,
    const EventEntry* entry,
    const sp<InputApplicationHandle>& applicationHandle,
    const sp<InputWindowHandle>& windowHandle,
    nsecs_t* nextWakeupTime, const char* reason) {
    if (applicationHandle == NULL && windowHandle == NULL) {
        if (mInputTargetWaitCause != INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY) {
            mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY;
            mInputTargetWaitStartTime = currentTime; //当前时间
            mInputTargetWaitTimeoutTime = LONG_LONG_MAX;
            mInputTargetWaitTimeoutExpired = false;
            mInputTargetWaitApplicationHandle.clear();
        }
    } else {
        if (mInputTargetWaitCause != INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY) {
            nsecs_t timeout;
            if (windowHandle != NULL) {
                timeout = windowHandle->getDispatchingTimeout(DEFAULT_INPUT_DISPATCHING_TIMEOUT);
            } else if (applicationHandle != NULL) {
                timeout = applicationHandle->getDispatchingTimeout(DEFAULT_INPUT_DISPATCHING_TIMEOUT);
            } else {
                timeout = DEFAULT_INPUT_DISPATCHING_TIMEOUT; // 5s
            }

            mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY;
            //这里的currentTime是指执行dispatchOnceInnerLocked方法体的起点
            mInputTargetWaitStartTime = currentTime; 
            mInputTargetWaitTimeoutTime = currentTime + timeout;
            mInputTargetWaitTimeoutExpired = false;
            mInputTargetWaitApplicationHandle.clear();

            if (windowHandle != NULL) {
                mInputTargetWaitApplicationHandle = windowHandle->inputApplicationHandle;
            }
            if (mInputTargetWaitApplicationHandle == NULL && applicationHandle != NULL) {
                mInputTargetWaitApplicationHandle = applicationHandle;
            }
        }
    }

    if (mInputTargetWaitTimeoutExpired) {
        return INPUT_EVENT_INJECTION_TIMED_OUT; //等待超时已过期,则直接返回
    }

    //当超时5s，则进入ANR流程
    if (currentTime >= mInputTargetWaitTimeoutTime) {
        onANRLocked(currentTime, applicationHandle, windowHandle,
                entry->eventTime, mInputTargetWaitStartTime, reason);

        *nextWakeupTime = LONG_LONG_MIN; //强制立刻执行轮询来执行ANR策略
        return INPUT_EVENT_INJECTION_PENDING;
    } else {
        if (mInputTargetWaitTimeoutTime < *nextWakeupTime) {
            *nextWakeupTime = mInputTargetWaitTimeoutTime; //当触发超时则强制执行轮询
        }
        return INPUT_EVENT_INJECTION_PENDING;
    }
}

ANR超时时间点为mInputTargetWaitTimeoutTime，该值等于currentTime + 5s, 这里的currentTime是指执行dispatchOnceInnerLocked方法体的起点。此处设置mInputTargetWaitCause等于INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY(应用没有准备就绪)，而前面resetANRTimeoutsLocked()过程是唯一用于重置等待理由的地方。

可见，ANR时间区间是从dispatchOnceInnerLocked方法体的起点，直到下次执行handleTargetsNotReadyLocked()方法的这段应用未准备就绪的时间段，该时间段是否超过5s来决定是否触发ANR。

当前这次的事件dispatch过程中执行findFocusedWindowTargetsLocked()方法到下一次执行resetANRTimeoutsLocked()的时间区间。

handleTargetsNotReadyLocked()的判断过程：

当applicationHandle和windowHandle同时为空, 且system准备就绪的情况下
- 设置等待理由 INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY;
- 设置超时等待时长为无限大;
- 设置TimeoutExpired= false
- 清空等待队列;
当applicationHandle和windowHandle至少一个不为空, 且application准备就绪的情况下:
- 设置等待理由 INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY;
- 设置超时等待时长为5s;
- 设置TimeoutExpired= false
- 清空等待队列;

继续回到[小节2.3]findFocusedWindowTargetsLocked，如果没有发生ANR，则addWindowTargetLocked()将该事件添加到inputTargets。

2.3.3 addWindowTargetLocked

void InputDispatcher::addWindowTargetLocked(const sp<InputWindowHandle>& windowHandle,
        int32_t targetFlags, BitSet32 pointerIds, Vector<InputTarget>& inputTargets) {
    inputTargets.push();

    const InputWindowInfo* windowInfo = windowHandle->getInfo();
    InputTarget& target = inputTargets.editTop();
    target.inputChannel = windowInfo->inputChannel;
    target.flags = targetFlags;
    target.xOffset = - windowInfo->frameLeft;
    target.yOffset = - windowInfo->frameTop;
    target.scaleFactor = windowInfo->scaleFactor;
    target.pointerIds = pointerIds;
}

将当前聚焦窗口mFocusedWindowHandle的inputChannel传递到inputTargets。

2.4 dispatchEventLocked

void InputDispatcher::dispatchEventLocked(nsecs_t currentTime,
        EventEntry* eventEntry, const Vector<InputTarget>& inputTargets) {
    //【见小节2.4.1】向mCommandQueue队列添加doPokeUserActivityLockedInterruptible命令
    pokeUserActivityLocked(eventEntry);

    for (size_t i = 0; i < inputTargets.size(); i++) {
        const InputTarget& inputTarget = inputTargets.itemAt(i);
        //[见小节2.4.3]
        ssize_t connectionIndex = getConnectionIndexLocked(inputTarget.inputChannel);
        if (connectionIndex >= 0) {
            sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);
            //找到目标连接[见小节２.5]
            prepareDispatchCycleLocked(currentTime, connection, eventEntry, &inputTarget);
        }
    }
}

该方法主要功能是将eventEntry发送到目标inputTargets．

其中pokeUserActivityLocked(eventEntry)方法最终会调用到Java层的PowerManagerService.java中的userActivityFromNative()方法．这也是PMS中唯一的native call方法．

2.4.1 pokeUserActivityLocked

void InputDispatcher::pokeUserActivityLocked(const EventEntry* eventEntry) {
    if (mFocusedWindowHandle != NULL) {
        const InputWindowInfo* info = mFocusedWindowHandle->getInfo();
        if (info->inputFeatures & InputWindowInfo::INPUT_FEATURE_DISABLE_USER_ACTIVITY) {
            return;
        }
    }
    ...
    //【见小节2.4.2】
    CommandEntry* commandEntry = postCommandLocked(
            & InputDispatcher::doPokeUserActivityLockedInterruptible);
    commandEntry->eventTime = eventEntry->eventTime;
    commandEntry->userActivityEventType = eventType;
}

2.4.2 postCommandLocked

InputDispatcher::CommandEntry* InputDispatcher::postCommandLocked(Command command) {
    CommandEntry* commandEntry = new CommandEntry(command);
    // 将命令加入mCommandQueue队尾
    mCommandQueue.enqueueAtTail(commandEntry);
    return commandEntry;
}

2.4.3 getConnectionIndexLocked

ssize_t InputDispatcher::getConnectionIndexLocked(const sp<InputChannel>& inputChannel) {
    ssize_t connectionIndex = mConnectionsByFd.indexOfKey(inputChannel->getFd());
    if (connectionIndex >= 0) {
        sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);
        if (connection->inputChannel.get() == inputChannel.get()) {
            return connectionIndex;
        }
    }
    return -1;
}

根据inputChannel的fd从mConnectionsByFd队列中查询目标connection.

2.5 prepareDispatchCycleLocked

void InputDispatcher::prepareDispatchCycleLocked(nsecs_t currentTime,
        const sp<Connection>& connection, EventEntry* eventEntry, const InputTarget* inputTarget) {

    if (connection->status != Connection::STATUS_NORMAL) {
        return;　//当连接已破坏,则直接返回
    }
    ...

    //[见小节2.6]
    enqueueDispatchEntriesLocked(currentTime, connection, eventEntry, inputTarget);
}

当connection状态不正确，则直接返回。

2.6 enqueueDispatchEntriesLocked

void InputDispatcher::enqueueDispatchEntriesLocked(nsecs_t currentTime,
        const sp<Connection>& connection, EventEntry* eventEntry, const InputTarget* inputTarget) {
    bool wasEmpty = connection->outboundQueue.isEmpty();

    //[见小节2.7]
    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);

    if (wasEmpty && !connection->outboundQueue.isEmpty()) {
        //当原先的outbound队列为空, 且当前outbound不为空的情况执行.[见小节2.8]
        startDispatchCycleLocked(currentTime, connection);
    }
}

该方法主要功能：

根据dispatchMode来分别执行DispatchEntry事件加入队列的操作。
当起初connection.outboundQueue等于空, 经enqueueDispatchEntryLocked处理后, outboundQueue不等于空情况下, 则执行startDispatchCycleLocked()方法.

2.7 enqueueDispatchEntryLocked

void InputDispatcher::enqueueDispatchEntryLocked(
        const sp<Connection>& connection, EventEntry* eventEntry, const InputTarget* inputTarget,
        int32_t dispatchMode) {
    int32_t inputTargetFlags = inputTarget->flags;
    if (!(inputTargetFlags & dispatchMode)) {
        return; //分发模式不匹配,则直接返回
    }
    inputTargetFlags = (inputTargetFlags & ~InputTarget::FLAG_DISPATCH_MASK) | dispatchMode;

    //生成新的事件, 加入connection的outbound队列
    DispatchEntry* dispatchEntry = new DispatchEntry(eventEntry,
            inputTargetFlags, inputTarget->xOffset, inputTarget->yOffset,
            inputTarget->scaleFactor);

    switch (eventEntry->type) {
        case EventEntry::TYPE_KEY: {
            KeyEntry* keyEntry = static_cast<KeyEntry*>(eventEntry);
            dispatchEntry->resolvedAction = keyEntry->action;
            dispatchEntry->resolvedFlags = keyEntry->flags;

            if (!connection->inputState.trackKey(keyEntry,
                    dispatchEntry->resolvedAction, dispatchEntry->resolvedFlags)) {
                delete dispatchEntry;
                return; //忽略不连续的事件
            }
            break;
        }
        ...
    }
    ...

    //添加到outboundQueue队尾
    connection->outboundQueue.enqueueAtTail(dispatchEntry);
}

该方法主要功能:

根据dispatchMode来决定是否需要加入outboundQueue队列;
根据EventEntry,来生成DispatchEntry事件;
将dispatchEntry加入到connection的outbound队列.

执行到这里,其实等于由做了一次搬运的工作,将InputDispatcher中mInboundQueue中的事件取出后, 找到目标window后,封装dispatchEntry加入到connection的outbound队列.

2.8 startDispatchCycleLocked

void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,
        const sp<Connection>& connection) {

    //当Connection状态正常,且outboundQueue不为空
    while (connection->status == Connection::STATUS_NORMAL
            && !connection->outboundQueue.isEmpty()) {
        DispatchEntry* dispatchEntry = connection->outboundQueue.head;
        dispatchEntry->deliveryTime = currentTime; //设置deliveryTime时间

        status_t status;
        EventEntry* eventEntry = dispatchEntry->eventEntry;
        switch (eventEntry->type) {
          case EventEntry::TYPE_KEY: {
              KeyEntry* keyEntry = static_cast<KeyEntry*>(eventEntry);

              //发布Key事件 [见小节2.9]
              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;
          }
          ...
        }

        if (status) { //publishKeyEvent失败情况
            if (status == WOULD_BLOCK) {
                if (connection->waitQueue.isEmpty()) {
                    //pipe已满,但waitQueue为空. 不正常的行为
                    abortBrokenDispatchCycleLocked(currentTime, connection, true /*notify*/);
                } else {
                    // 处于阻塞状态
                    connection->inputPublisherBlocked = true;
                }
            } else {
                //不不正常的行为
                abortBrokenDispatchCycleLocked(currentTime, connection, true /*notify*/);
            }
            return;
        }

        //从outboundQueue中取出事件,重新放入waitQueue队列
        connection->outboundQueue.dequeue(dispatchEntry);
        connection->waitQueue.enqueueAtTail(dispatchEntry);

    }
}

startDispatchCycleLocked的主要功能: 从outboundQueue中取出事件,重新放入waitQueue队列

startDispatchCycleLocked触发时机：当起初connection.outboundQueue等于空, 经enqueueDispatchEntryLocked处理后, outboundQueue不等于空。
startDispatchCycleLocked主要功能: 从outboundQueue中取出事件,重新放入waitQueue队列
publishKeyEvent执行结果status不等于OK的情况下：
- WOULD_BLOCK，且waitQueue等于空，则调用abortBrokenDispatchCycleLocked()，该方法最终会调用到Java层的IMS.notifyInputChannelBroken().
- WOULD_BLOCK，且waitQueue不等于空，则处于阻塞状态，即inputPublisherBlocked=true
- 其他情况，则调用abortBrokenDispatchCycleLocked
abortBrokenDispatchCycleLocked()方法最终会调用到Java层的IMS.notifyInputChannelBroken().

2.9 inputPublisher.publishKeyEvent

[-> InputTransport.cpp]

status_t InputPublisher::publishKeyEvent(...) {
    if (!seq) {
        return BAD_VALUE;
    }

    InputMessage msg;
    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;
    //通过InputChannel来发送消息
    return mChannel->sendMessage(&msg);
}

InputChannel通过socket向远端的socket发送消息。socket通道是如何建立的呢？ InputDispatcher又是如何与前台的window通信的呢？我后边会另写一篇文章详细分析，这里暂且不做讨论.

2.10 releasePendingEventLocked

void InputDispatcher::releasePendingEventLocked() {
    if (mPendingEvent) {
        resetANRTimeoutsLocked(); //重置ANR超时时间
        releaseInboundEventLocked(mPendingEvent); //释放mPendingEvent对象,并记录到mRecentQueue队列
        mPendingEvent = NULL; //置空mPendingEvent变量.
    }
}

三. 处理Comand

3.1 runCommandsLockedInterruptible

bool InputDispatcher::runCommandsLockedInterruptible() {
    if (mCommandQueue.isEmpty()) {
        return false;
    }

    do {
        //从mCommandQueue队列的头部取出第一个元素
        CommandEntry* commandEntry = mCommandQueue.dequeueAtHead();

        Command command = commandEntry->command;
        //此处调用的命令隐式地包含'LockedInterruptible'
        (this->*command)(commandEntry);

        commandEntry->connection.clear();
        delete commandEntry;
    } while (! mCommandQueue.isEmpty());
    return true;
}

通过循环方式处理完mCommandQueue队列的所有命令，处理过程从mCommandQueue中取出CommandEntry.

typedef void (InputDispatcher::*Command)(CommandEntry* commandEntry);
struct CommandEntry : Link<CommandEntry> {
    CommandEntry(Command command);

    Command command;
    sp<Connection> connection;
    nsecs_t eventTime;
    KeyEntry* keyEntry;
    sp<InputApplicationHandle> inputApplicationHandle;
    sp<InputWindowHandle> inputWindowHandle;
    String8 reason;
    int32_t userActivityEventType;
    uint32_t seq;
    bool handled;
};

前面小节【2.4.1】添加的doPokeUserActivityLockedInterruptible命令. 接下来进入该方法：

3.2 doPokeUserActivityLockedInterruptible

[-> InputDispatcher]

void InputDispatcher::doPokeUserActivityLockedInterruptible(CommandEntry* commandEntry) {
    mLock.unlock();
    //【见小节4.3】
    mPolicy->pokeUserActivity(commandEntry->eventTime, commandEntry->userActivityEventType);

    mLock.lock();
}

3.3 pokeUserActivity

[-> com_android_server_input_InputManagerService.cpp]

void NativeInputManager::pokeUserActivity(nsecs_t eventTime, int32_t eventType) {
    //[见小节4.4]
    android_server_PowerManagerService_userActivity(eventTime, eventType);
}

3.4 android_server_PowerManagerService_userActivity

[-> com_android_server_power_PowerManagerService.cpp]

void android_server_PowerManagerService_userActivity(nsecs_t eventTime, int32_t eventType) {
    // Tell the power HAL when user activity occurs.
    if (gPowerModule && gPowerModule->powerHint) {
        gPowerModule->powerHint(gPowerModule, POWER_HINT_INTERACTION, NULL);
    }

    if (gPowerManagerServiceObj) {
        ...
        //[见小节4.5]
        env->CallVoidMethod(gPowerManagerServiceObj,
                gPowerManagerServiceClassInfo.userActivityFromNative,
                nanoseconds_to_milliseconds(eventTime), eventType, 0);
    }
}

3.5 PMS.userActivityFromNative

[-> PowerManagerService.java]

private void userActivityFromNative(long eventTime, int event, int flags) {
    userActivityInternal(eventTime, event, flags, Process.SYSTEM_UID);
}

private void userActivityInternal(long eventTime, int event, int flags, int uid) {
    synchronized (mLock) {
        if (userActivityNoUpdateLocked(eventTime, event, flags, uid)) {
            updatePowerStateLocked();
        }
    }
}

runCommandsLockedInterruptible是不断地从mCommandQueue队列取出命令，然后执行直到全部执行完成。除了doPokeUserActivityLockedInterruptible，还有其他如下命令：

doNotifyANRLockedInterruptible
doInterceptKeyBeforeDispatchingLockedInterruptible
doDispatchCycleFinishedLockedInterruptible
doNotifyInputChannelBrokenLockedInterruptible
doNotifyConfigurationChangedInterruptible

四. 总结

4.1 流程图

input_dispatcher_seq

4.2 核心方法

用一张图来整体概况InputDispatcher线程的主要工作：

input_dispatcher

图解:

dispatchOnceInnerLocked(): 从InputDispatcher的mInboundQueue队列，取出事件EventEntry。另外该方法开始执行的时间点(currentTime)便是后续事件dispatchEntry的分发时间(deliveryTime）
dispatchKeyLocked()：满足一定条件时会添加命令doInterceptKeyBeforeDispatchingLockedInterruptible；
enqueueDispatchEntryLocked()：生成事件DispatchEntry并加入connection的outbound队列
startDispatchCycleLocked()：从outboundQueue中取出事件DispatchEntry, 重新放入connection的waitQueue队列；
InputChannel.sendMessage通过socket方式将消息发送给远程进程；
runCommandsLockedInterruptible()：通过循环遍历地方式，依次处理mCommandQueue队列中的所有命令。而mCommandQueue队列中的命令是通过postCommandLocked()方式向该队列添加的。

本篇博文我们来学习下InputDispatcher线程的业务逻辑过程