input 按键分发

文章出处：http://blog.csdn.net/shift_wwx/article/details/49764595

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之前InputManager 的启动过程 已经对inputManager 的启动过程做了简单的介绍。这里先小结一下：

1、InputManagerService 构造，确认DisplayThread，做nativeInit

2、nativeInit ，创建一些实例，例如NativeInputManager、InputManager、EventHub

3、构造InputManager，实例 InputReader、InputDispatcher，并实例 InputReaderThread 对按键进行监控、InputDispatcherThread 对按键进行分发。

对于监控，是根据EventHub来的，这里说一下分发

InputReaderThread线程会不断地循环调用InputReader.loopOnce函数来读入键盘事件，而实际的键盘事件读入操作是由EventHub.getEvent函数来进行的。如果当前没有键盘事件发生，InputReaderThread线程就会睡眠在EventHub.getEvent函数上，而当键盘事件发生后，就会把这个事件封装成一个RawEvent对象，然后返回到loopOnce函数中，执行process函数进一步处理：

processEventsLocked(mEventBuffer, count);

processEventsForDeviceLocked(deviceId, rawEvent, batchSize);

void InputReader::processEventsForDeviceLocked(int32_t deviceId,
        const RawEvent* rawEvents, size_t count) {
    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
    if (deviceIndex < 0) {
        ALOGW("Discarding event for unknown deviceId %d.", deviceId);
        return;
    }

    InputDevice* device = mDevices.valueAt(deviceIndex);
    if (device->isIgnored()) {
        //ALOGD("Discarding event for ignored deviceId %d.", deviceId);
        return;
    }

    device->process(rawEvents, count);
}

void InputDevice::process(const RawEvent* rawEvents, size_t count) {
    // Process all of the events in order for each mapper.
    // We cannot simply ask each mapper to process them in bulk because mappers may
    // have side-effects that must be interleaved.  For example, joystick movement events and
    // gamepad button presses are handled by different mappers but they should be dispatched
    // in the order received.
    size_t numMappers = mMappers.size();
    for (const RawEvent* rawEvent = rawEvents; count--; rawEvent++) {
#if DEBUG_RAW_EVENTS
        ALOGD("Input event: device=%d type=0x%04x code=0x%04x value=0x%08x when=%lld",
                rawEvent->deviceId, rawEvent->type, rawEvent->code, rawEvent->value,
                rawEvent->when);
#endif

        if (mDropUntilNextSync) {
            if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
                mDropUntilNextSync = false;
#if DEBUG_RAW_EVENTS
                ALOGD("Recovered from input event buffer overrun.");
#endif
            } else {
#if DEBUG_RAW_EVENTS
                ALOGD("Dropped input event while waiting for next input sync.");
#endif
            }
        } else if (rawEvent->type == EV_SYN && rawEvent->code == SYN_DROPPED) {
            ALOGI("Detected input event buffer overrun for device %s.", getName().string());
            mDropUntilNextSync = true;
            reset(rawEvent->when);
        } else {
            for (size_t i = 0; i < numMappers; i++) {
                InputMapper* mapper = mMappers[i];
                mapper->process(rawEvent);
            }
        }
    }
}

这里的mMapper成员变量保存了一系列输入设备事件处理象，例如负责处理键盘事件的KeyboardKeyMapper对象、负责处理轨迹球事件的TrackballInputMapper对象以及负责处理触摸屏事件的TouchInputMapper对象， 它们是在InputReader类的成员函数createDevice中创建的。这里查询每一个InputMapper对象是否要对当前发生的事件进行处理。由于发生的是键盘事件，真正会对该事件进行处理的只有KeyboardKeyMapper对象。

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;
            uint32_t flags;
            if (getEventHub()->mapKey(getDeviceId(), scanCode, usageCode, &keyCode, &flags)) {
                keyCode = AKEYCODE_UNKNOWN;
                flags = 0;
            }
            processKey(rawEvent->when, rawEvent->value != 0, keyCode, scanCode, flags);
        }
        break;
    }
    case EV_MSC: {
        if (rawEvent->code == MSC_SCAN) {
            mCurrentHidUsage = rawEvent->value;
        }
        break;
    }
    case EV_SYN: {
        if (rawEvent->code == SYN_REPORT) {
            mCurrentHidUsage = 0;
        }
    }
    }
}

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

    if (down) {
        // Rotate key codes according to orientation if needed.
        if (mParameters.orientationAware && mParameters.hasAssociatedDisplay) {
            keyCode = rotateKeyCode(keyCode, mOrientation);
        }

        // Add key down.
        ssize_t keyDownIndex = findKeyDown(scanCode);
        if (keyDownIndex >= 0) {
            // key repeat, be sure to use same keycode as before in case of rotation
            keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;
        } else {
            // key down
            if ((policyFlags & POLICY_FLAG_VIRTUAL)
                    && mContext->shouldDropVirtualKey(when,
                            getDevice(), keyCode, scanCode)) {
                return;
            }

            mKeyDowns.push();
            KeyDown& keyDown = mKeyDowns.editTop();
            keyDown.keyCode = keyCode;
            keyDown.scanCode = scanCode;
        }

        mDownTime = when;
    } else {
        // Remove key down.
        ssize_t keyDownIndex = findKeyDown(scanCode);
        if (keyDownIndex >= 0) {
            // key up, be sure to use same keycode as before in case of rotation
            keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;
            mKeyDowns.removeAt(size_t(keyDownIndex));
        } else {
            // key was not actually down
            ALOGI("Dropping key up from device %s because the key was not down.  "
                    "keyCode=%d, scanCode=%d",
                    getDeviceName().string(), keyCode, scanCode);
            return;
        }
    }

    int32_t oldMetaState = mMetaState;
    int32_t newMetaState = updateMetaState(keyCode, down, oldMetaState);
    bool metaStateChanged = oldMetaState != newMetaState;
    if (metaStateChanged) {
        mMetaState = newMetaState;
        updateLedState(false);
    }

    nsecs_t downTime = mDownTime;

    if (metaStateChanged) {
        getContext()->updateGlobalMetaState();
    }

    if (down && !isMetaKey(keyCode)) {
        getContext()->fadePointer();
    }

    NotifyKeyArgs args(when, getDeviceId(), mSource, policyFlags,
            down ? AKEY_EVENT_ACTION_DOWN : AKEY_EVENT_ACTION_UP,
            AKEY_EVENT_FLAG_FROM_SYSTEM, keyCode, scanCode, newMetaState, downTime);
    getListener()->notifyKey(&args);
}

这个函数首先对按键作一些处理，例如，当某一个DPAD键被按下时，根据当时屏幕方向的不同，它所表示的意义也不同，因此，这里需要根据当时屏幕的方向来调整键盘码：

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

 如果这个键是一直按着不放的，不管屏幕的方向如何，必须保证后面的键盘码和前面的一样：

ssize_t keyDownIndex = findKeyDown(scanCode);

 如果是第一次按下某个键，还必须把它保存在mLocked.keyDowns里面，就是为了处理上面讲的当这个键盘一直按着不放的时候屏幕方向发生改变的情况。
如果是松开键盘上的某个键，就把它从mLocked.keyDowns里面删除：

    ssize_t keyDownIndex = findKeyDown(scanCode);
    if (keyDownIndex >= 0) {
        // key up, be sure to use same keycode as before in case of rotation
        keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;
        mKeyDowns.removeAt(size_t(keyDownIndex));
    } else {
        // key was not actually down
        ALOGI("Dropping key up from device %s because the key was not down.  "
                "keyCode=%d, scanCode=%d",
                getDeviceName().string(), keyCode, scanCode);
        return;
    }

最后是调用notifyKey：

getListener()->notifyKey(&args);

---->

InputListenerInterface* InputReader::ContextImpl::getListener() {
    return mReader->mQueuedListener.get();
}

---->

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

到这里，我们返回 loopOnce：

    // Send out a message that the describes the changed input devices.
    if (inputDevicesChanged) {
        mPolicy->notifyInputDevicesChanged(inputDevices);
    }

    // Flush queued events out to the listener.
    // This must happen outside of the lock because the listener could potentially call
    // back into the InputReader's methods, such as getScanCodeState, or become blocked
    // on another thread similarly waiting to acquire the InputReader lock thereby
    // resulting in a deadlock.  This situation is actually quite plausible because the
    // listener is actually the input dispatcher, which calls into the window manager,
    // which occasionally calls into the input reader.
    mQueuedListener->flush();

如果input device 发生改变的话，会通过notigyInputDevicesChanged 通知上层。

最后会通过mQueuedListener 的flush 激活 InputDispatcher。

通过之前code 看到，processEventsLocked 会将获取的event 以NotifyKeyArgs 的形式存放起来，这里怎么会激活 InputDispatcher呢？

看一下 InputManager 的构造函数：

InputManager::InputManager(
        const sp& eventHub,
        const sp& readerPolicy,
        const sp& dispatcherPolicy) {
    mDispatcher = new InputDispatcher(dispatcherPolicy);
    mReader = new InputReader(eventHub, readerPolicy, mDispatcher);
    initialize();
}

mReader 的第三个参数就是mDispatcher，再来看看InputReader 的构造：

InputReader::InputReader(const sp& eventHub,
        const sp& policy,
        const sp& listener) :
        mContext(this), mEventHub(eventHub), mPolicy(policy),
        mGlobalMetaState(0), mGeneration(1),
        mDisableVirtualKeysTimeout(LLONG_MIN), mNextTimeout(LLONG_MAX),
        mConfigurationChangesToRefresh(0) {
    mQueuedListener = new QueuedInputListener(listener);

    { // acquire lock
        AutoMutex _l(mLock);

        refreshConfigurationLocked(0);
        updateGlobalMetaStateLocked();
    } // release lock
}

第三个参数传进来是 mDispatcher，到这里就变成了mQueuedListener。
所以上面的flush 其实调用的就是 InputDispatcher 的 notifyKey：

void InputDispatcher::notifyKey(const NotifyKeyArgs* args) {
#if DEBUG_INBOUND_EVENT_DETAILS
    ALOGD("notifyKey - eventTime=%lld, deviceId=%d, source=0x%x, policyFlags=0x%x, action=0x%x, "
            "flags=0x%x, keyCode=0x%x, scanCode=0x%x, metaState=0x%x, downTime=%lld",
            args->eventTime, args->deviceId, args->source, args->policyFlags,
            args->action, args->flags, args->keyCode, args->scanCode,
            args->metaState, args->downTime);
#endif
    if (!validateKeyEvent(args->action)) {
        return;
    }

    uint32_t policyFlags = args->policyFlags;
    int32_t flags = args->flags;
    int32_t metaState = args->metaState;
    if ((policyFlags & POLICY_FLAG_VIRTUAL) || (flags & AKEY_EVENT_FLAG_VIRTUAL_HARD_KEY)) {
        policyFlags |= POLICY_FLAG_VIRTUAL;
        flags |= AKEY_EVENT_FLAG_VIRTUAL_HARD_KEY;
    }
    if (policyFlags & POLICY_FLAG_FUNCTION) {
        metaState |= AMETA_FUNCTION_ON;
    }

    policyFlags |= POLICY_FLAG_TRUSTED;

    int32_t keyCode = args->keyCode;
    if (metaState & AMETA_META_ON && args->action == AKEY_EVENT_ACTION_DOWN) {
        int32_t newKeyCode = AKEYCODE_UNKNOWN;
        if (keyCode == AKEYCODE_DEL) {
            newKeyCode = AKEYCODE_BACK;
        } else if (keyCode == AKEYCODE_ENTER) {
            newKeyCode = AKEYCODE_HOME;
        }
        if (newKeyCode != AKEYCODE_UNKNOWN) {
            AutoMutex _l(mLock);
            struct KeyReplacement replacement = {keyCode, args->deviceId};
            mReplacedKeys.add(replacement, newKeyCode);
            keyCode = newKeyCode;
            metaState &= ~AMETA_META_ON;
        }
    } else if (args->action == AKEY_EVENT_ACTION_UP) {
        // In order to maintain a consistent stream of up and down events, check to see if the key
        // going up is one we've replaced in a down event and haven't yet replaced in an up event,
        // even if the modifier was released between the down and the up events.
        AutoMutex _l(mLock);
        struct KeyReplacement replacement = {keyCode, args->deviceId};
        ssize_t index = mReplacedKeys.indexOfKey(replacement);
        if (index >= 0) {
            keyCode = mReplacedKeys.valueAt(index);
            mReplacedKeys.removeItemsAt(index);
            metaState &= ~AMETA_META_ON;
        }
    }

    KeyEvent event;
    event.initialize(args->deviceId, args->source, args->action,
            flags, keyCode, args->scanCode, metaState, 0,
            args->downTime, args->eventTime);

    mPolicy->interceptKeyBeforeQueueing(&event, /*byref*/ policyFlags);

    bool needWake;
    { // acquire lock
        mLock.lock();

        if (shouldSendKeyToInputFilterLocked(args)) {
            mLock.unlock();

            policyFlags |= POLICY_FLAG_FILTERED;
            if (!mPolicy->filterInputEvent(&event, policyFlags)) {
                return; // event was consumed by the filter
            }

            mLock.lock();
        }

        int32_t repeatCount = 0;
        KeyEntry* newEntry = new KeyEntry(args->eventTime,
                args->deviceId, args->source, policyFlags,
                args->action, flags, keyCode, args->scanCode,
                metaState, repeatCount, args->downTime);

        needWake = enqueueInboundEventLocked(newEntry);
        mLock.unlock();
    } // release lock

    if (needWake) {
        mLooper->wake();
    }
}

 函数首先是调用validateKeyEvent函数来验证action参数是否正确：

    if (!validateKeyEvent(args->action)) {
        return;
    }

static bool isValidKeyAction(int32_t action) {
    switch (action) {
    case AKEY_EVENT_ACTION_DOWN:
    case AKEY_EVENT_ACTION_UP:
        return true;
    default:
        return false;
    }
}

正确的action参数的值只能为AKEY_EVENT_ACTION_DOWN（按下）或者AKEY_EVENT_ACTION_UP（松开）。

接着是在进queue 之前做一些必须要的操作：

    KeyEvent event;
    event.initialize(args->deviceId, args->source, args->action,
            flags, keyCode, args->scanCode, metaState, 0,
            args->downTime, args->eventTime);

    mPolicy->interceptKeyBeforeQueueing(&event, /*byref*/ policyFlags)

这个会通过jni 回调到InputManagerService.java 中的接口，也就是 InputManager 的启动过程中提到的WindowManagerCallbacks。
最后调用enqueueInboundEventLocked函数把这个按键事件封装成一个KeyEntry结构加入到InputDispatcher类的mInboundQueue队列中去：

    int32_t repeatCount = 0;
    KeyEntry* newEntry = new KeyEntry(args->eventTime,
            args->deviceId, args->source, policyFlags,
            args->action, flags, keyCode, args->scanCode,
            metaState, repeatCount, args->downTime);

    needWake = enqueueInboundEventLocked(newEntry);

bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) {
    bool needWake = mInboundQueue.isEmpty();
    mInboundQueue.enqueueAtTail(entry);
    traceInboundQueueLengthLocked();

    switch (entry->type) {
    case EventEntry::TYPE_KEY: {
        // Optimize app switch latency.
        // If the application takes too long to catch up then we drop all events preceding
        // the app switch key.
        KeyEntry* keyEntry = static_cast(entry);
        if (isAppSwitchKeyEventLocked(keyEntry)) {
            if (keyEntry->action == AKEY_EVENT_ACTION_DOWN) {
                mAppSwitchSawKeyDown = true;
            } else if (keyEntry->action == AKEY_EVENT_ACTION_UP) {
                if (mAppSwitchSawKeyDown) {
#if DEBUG_APP_SWITCH
                    ALOGD("App switch is pending!");
#endif
                    mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;
                    mAppSwitchSawKeyDown = false;
                    needWake = true;
                }
            }
        }
        break;
    }

    case EventEntry::TYPE_MOTION: {
        // Optimize case where the current application is unresponsive and the user
        // decides to touch a window in a different application.
        // If the application takes too long to catch up then we drop all events preceding
        // the touch into the other window.
        MotionEntry* motionEntry = static_cast(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));
            sp touchedWindowHandle = findTouchedWindowAtLocked(displayId, x, y);
            if (touchedWindowHandle != NULL
                    && touchedWindowHandle->inputApplicationHandle
                            != mInputTargetWaitApplicationHandle) {
                // User touched a different application than the one we are waiting on.
                // Flag the event, and start pruning the input queue.
                mNextUnblockedEvent = motionEntry;
                needWake = true;
            }
        }
        break;
    }
    }

    return needWake;
}

从这个函数我们可以看出，在两种情况下，它的返回值为true，一是当加入该键盘事件到mInboundQueue之前，mInboundQueue为空，这表示InputDispatcherThread线程正在睡眠等待InputReaderThread线程的唤醒，因此，它返回true表示要唤醒InputDispatccherThread线程；二是加入该键盘事件到mInboundQueue之前，mInboundQueue不为空，但是此时用户按下的是Home键，按下Home键表示要切换App，我们知道，在切换App时，新的App会把它的键盘消息接收通道注册到InputDispatcher中去，并且会等待InputReader的唤醒，因此，在这种情况下，也需要返回true，表示要唤醒InputDispatccherThread线程。如果不是这两种情况，那么就说明InputDispatccherThread线程现在正在处理前面的键盘事件，不需要唤醒它。
回到前面的notifyKey函数中，根据enqueueInboundEventLocked函数的返回值来决定是否要唤醒InputDispatccherThread线程：

    if (needWake) {
        mLooper->wake();
    }

 这里，假设needWake为true，于是，就会调用mLooper对象的wake函数来唤醒InputDispatccherThread线程了。

InputManager 的启动过程中说到过 InputReaderThread 和 InputDispatcherThread，在InputDispatccherThread 被唤醒的时候，会调用：

bool InputDispatcherThread::threadLoop() {
    mDispatcher->dispatchOnce();
    return true;
}

void InputDispatcher::dispatchOnce() {
    nsecs_t nextWakeupTime = LONG_LONG_MAX;
    { // acquire lock
        AutoMutex _l(mLock);
        mDispatcherIsAliveCondition.broadcast();

        // Run a dispatch loop if there are no pending commands.
        // The dispatch loop might enqueue commands to run afterwards.
        if (!haveCommandsLocked()) {
            dispatchOnceInnerLocked(&nextWakeupTime);
        }

        // Run all pending commands if there are any.
        // If any commands were run then force the next poll to wake up immediately.
        if (runCommandsLockedInterruptible()) {
            nextWakeupTime = LONG_LONG_MIN;
        }
    } // release lock

    // Wait for callback or timeout or wake.  (make sure we round up, not down)
    nsecs_t currentTime = now();
    int timeoutMillis = toMillisecondTimeoutDelay(currentTime, nextWakeupTime);
    mLooper->pollOnce(timeoutMillis);
}

它调用dispatchOnceInnerLocked函数来进一步处理这个键盘事件。

void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) {
    nsecs_t currentTime = now();

    // Reset the key repeat timer whenever normal dispatch is suspended while the
    // device is in a non-interactive state.  This is to ensure that we abort a key
    // repeat if the device is just coming out of sleep.
    if (!mDispatchEnabled) {
        resetKeyRepeatLocked();
    }

    // If dispatching is frozen, do not process timeouts or try to deliver any new events.
    if (mDispatchFrozen) {
#if DEBUG_FOCUS
        ALOGD("Dispatch frozen.  Waiting some more.");
#endif
        return;
    }

    // Optimize latency of app switches.
    // Essentially we start a short timeout when an app switch key (HOME / ENDCALL) has
    // been pressed.  When it expires, we preempt dispatch and drop all other pending events.
    bool isAppSwitchDue = mAppSwitchDueTime <= currentTime;
    if (mAppSwitchDueTime < *nextWakeupTime) {
        *nextWakeupTime = mAppSwitchDueTime;
    }

    // Ready to start a new event.
    // If we don't already have a pending event, go grab one.
    if (! mPendingEvent) {
        if (mInboundQueue.isEmpty()) {
            if (isAppSwitchDue) {
                // The inbound queue is empty so the app switch key we were waiting
                // for will never arrive.  Stop waiting for it.
                resetPendingAppSwitchLocked(false);
                isAppSwitchDue = false;
            }

            // Synthesize a key repeat if appropriate.
            if (mKeyRepeatState.lastKeyEntry) {
                if (currentTime >= mKeyRepeatState.nextRepeatTime) {
                    mPendingEvent = synthesizeKeyRepeatLocked(currentTime);
                } else {
                    if (mKeyRepeatState.nextRepeatTime < *nextWakeupTime) {
                        *nextWakeupTime = mKeyRepeatState.nextRepeatTime;
                    }
                }
            }

            // Nothing to do if there is no pending event.
            if (!mPendingEvent) {
                return;
            }
        } else {
            // Inbound queue has at least one entry.
            mPendingEvent = mInboundQueue.dequeueAtHead();
            traceInboundQueueLengthLocked();
        }

        // Poke user activity for this event.
        if (mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER) {
            pokeUserActivityLocked(mPendingEvent);
        }

        // Get ready to dispatch the event.
        resetANRTimeoutsLocked();
    }

    // Now we have an event to dispatch.
    // All events are eventually dequeued and processed this way, even if we intend to drop them.
    ALOG_ASSERT(mPendingEvent != NULL);
    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;
    }

    if (mNextUnblockedEvent == mPendingEvent) {
        mNextUnblockedEvent = NULL;
    }

    switch (mPendingEvent->type) {
    case EventEntry::TYPE_CONFIGURATION_CHANGED: {
        ConfigurationChangedEntry* typedEntry =
                static_cast(mPendingEvent);
        done = dispatchConfigurationChangedLocked(currentTime, typedEntry);
        dropReason = DROP_REASON_NOT_DROPPED; // configuration changes are never dropped
        break;
    }

    case EventEntry::TYPE_DEVICE_RESET: {
        DeviceResetEntry* typedEntry =
                static_cast(mPendingEvent);
        done = dispatchDeviceResetLocked(currentTime, typedEntry);
        dropReason = DROP_REASON_NOT_DROPPED; // device resets are never dropped
        break;
    }

    case EventEntry::TYPE_KEY: {
        KeyEntry* typedEntry = static_cast(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;
        }
        done = dispatchKeyLocked(currentTime, typedEntry, &dropReason, nextWakeupTime);
        break;
    }

    case EventEntry::TYPE_MOTION: {
        MotionEntry* typedEntry = static_cast(mPendingEvent);
        if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) {
            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;
        }
        done = dispatchMotionLocked(currentTime, typedEntry,
                &dropReason, nextWakeupTime);
        break;
    }

    default:
        ALOG_ASSERT(false);
        break;
    }

    if (done) {
        if (dropReason != DROP_REASON_NOT_DROPPED) {
            dropInboundEventLocked(mPendingEvent, dropReason);
        }

        releasePendingEventLocked();
        *nextWakeupTime = LONG_LONG_MIN;  // force next poll to wake up immediately
    }
}

逻辑忽略先，最后会调用：

done = dispatchKeyLocked(currentTime, typedEntry, &dropReason, nextWakeupTime);

bool InputDispatcher::dispatchKeyLocked(nsecs_t currentTime, KeyEntry* entry,
        DropReason* dropReason, nsecs_t* nextWakeupTime) {
    ......
    
    // Identify targets.
    Vector inputTargets;
    int32_t injectionResult = findFocusedWindowTargetsLocked(currentTime,
            entry, inputTargets, nextWakeupTime);
    if (injectionResult == INPUT_EVENT_INJECTION_PENDING) {
        return false;
    }

    setInjectionResultLocked(entry, injectionResult);
    if (injectionResult != INPUT_EVENT_INJECTION_SUCCEEDED) {
        return true;
    }

    addMonitoringTargetsLocked(inputTargets);

    // Dispatch the key.
    dispatchEventLocked(currentTime, entry, inputTargets);
    return true;
}