void InputDispatcher::notifyMotion(const NotifyMotionArgs* args) {
    if (!validateMotionEvent(args->action, args->actionButton, args->pointerCount,
                             args->pointerProperties)) {
        return;
    }
    uint32_t policyFlags = args->policyFlags;
    // 來(lái)自InputReader/InputClassifier的 motion 事件，都是受信任的
    policyFlags |= POLICY_FLAG_TRUSTED;
    android::base::Timer t;
    // 1. 對(duì)觸摸事件執(zhí)行截?cái)嗖呗?
    // 觸摸事件入隊(duì)前，查詢截?cái)嗖呗?，查詢的結(jié)果保存到參數(shù) policyFlags
    mPolicy->interceptMotionBeforeQueueing(args->displayId, args->eventTime, /*byref*/ policyFlags);
    if (t.duration() > SLOW_INTERCEPTION_THRESHOLD) {
        ALOGW("Excessive delay in interceptMotionBeforeQueueing; took %s ms",
              std::to_string(t.duration().count()).c_str());
    }
    bool needWake;
    { // acquire lock
        mLock.lock();
        if (shouldSendMotionToInputFilterLocked(args)) {
            // ...
        }
        // 包裝成 MotionEntry
        // Just enqueue a new motion event.
        std::unique_ptr<MotionEntry> newEntry =
                std::make_unique<MotionEntry>(args->id, args->eventTime, args->deviceId,
                                              args->source, args->displayId, policyFlags,
                                              args->action, args->actionButton, args->flags,
                                              args->metaState, args->buttonState,
                                              args->classification, args->edgeFlags,
                                              args->xPrecision, args->yPrecision,
                                              args->xCursorPosition, args->yCursorPosition,
                                              args->downTime, args->pointerCount,
                                              args->pointerProperties, args->pointerCoords, 0, 0);
        // 2. 把觸摸事件加入收件箱
        needWake = enqueueInboundEventLocked(std::move(newEntry));
        mLock.unlock();
    } // release lock
    // 3. 如果有必要，喚醒線程處理觸摸事件
    if (needWake) {
        mLooper->wake();
    }
}

void InputDispatcher::dispatchOnce() {
    nsecs_t nextWakeupTime = LONG_LONG_MAX;
    { // acquire lock
        std::scoped_lock _l(mLock);
        mDispatcherIsAlive.notify_all();
        if (!haveCommandsLocked()) {
            // 1. 分發(fā)一個(gè)觸摸事件
            dispatchOnceInnerLocked(&nextWakeupTime);
        }
        // 觸摸事件的分發(fā)過(guò)程不會(huì)產(chǎn)生命令
        if (runCommandsLockedInterruptible()) {
            nextWakeupTime = LONG_LONG_MIN;
        }
        // 2. 計(jì)算線程下次喚醒的時(shí)間點(diǎn)，以便處理 anr
        const nsecs_t nextAnrCheck = processAnrsLocked();
        nextWakeupTime = std::min(nextWakeupTime, nextAnrCheck);
        if (nextWakeupTime == LONG_LONG_MAX) {
            mDispatcherEnteredIdle.notify_all();
        }
    } // release lock
    // 3. 線程休眠指定的時(shí)長(zhǎng)
    nsecs_t currentTime = now();
    int timeoutMillis = toMillisecondTimeoutDelay(currentTime, nextWakeupTime);
    mLooper->pollOnce(timeoutMillis);
}

void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) {
    nsecs_t currentTime = now();
    if (!mDispatchEnabled) {
        resetKeyRepeatLocked();
    }
    if (mDispatchFrozen) {
        return;
    }
    // 這里是優(yōu)化 app 切換的延遲
    // mAppSwitchDueTime 是 app 切換的超時(shí)時(shí)間，如果小于當(dāng)前時(shí)間，那么表明app切換超時(shí)了
    // 如果app切換超時(shí)，那么在app切換按鍵事件之前的未處理的事件，都將會(huì)被丟棄
    bool isAppSwitchDue = mAppSwitchDueTime <= currentTime;
    if (mAppSwitchDueTime < *nextWakeupTime) {
        *nextWakeupTime = mAppSwitchDueTime;
    }
    // mPendingEvent 表示正在處理的事件
    if (!mPendingEvent) {
        if (mInboundQueue.empty()) {
            // ...
        } else {
            // 1. 從收件箱隊(duì)列中取出事件
            mPendingEvent = mInboundQueue.front();
            mInboundQueue.pop_front();
            traceInboundQueueLengthLocked();
        }
        // 如果這個(gè)事件需要傳遞給用戶，那么需要同上層的 PowerManagerService，此時(shí)有用戶行為，這個(gè)作用就是延長(zhǎng)亮屏的時(shí)間
        if (mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER) {
            pokeUserActivityLocked(*mPendingEvent);
        }
    }
    ALOG_ASSERT(mPendingEvent != nullptr);
    bool done = false;
    // 檢測(cè)丟棄事件的原因
    DropReason dropReason = DropReason::NOT_DROPPED;
    if (!(mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER)) {
        // 被截?cái)嗖呗越財(cái)?
        dropReason = DropReason::POLICY;
    } else if (!mDispatchEnabled) {
        // 一般是由于系統(tǒng)正在系統(tǒng)或者正在關(guān)閉
        dropReason = DropReason::DISABLED;
    }
    if (mNextUnblockedEvent == mPendingEvent) {
        mNextUnblockedEvent = nullptr;
    }
    switch (mPendingEvent->type) {
        // ....
        case EventEntry::Type::MOTION: {
            std::shared_ptr<MotionEntry> motionEntry =
                    std::static_pointer_cast<MotionEntry>(mPendingEvent);
            if (dropReason == DropReason::NOT_DROPPED && isAppSwitchDue) {
                // app 切換超時(shí)，導(dǎo)致觸摸事件被丟棄
                dropReason = DropReason::APP_SWITCH;
            }
            if (dropReason == DropReason::NOT_DROPPED && isStaleEvent(currentTime, *motionEntry)) {
                // 10s 之前的事件，已經(jīng)過(guò)期
                dropReason = DropReason::STALE;
            }
            // 這里是優(yōu)化應(yīng)用無(wú)響應(yīng)的一個(gè)措施，會(huì)丟棄mNextUnblockedEvent之前的所有觸摸事件
            if (dropReason == DropReason::NOT_DROPPED && mNextUnblockedEvent) {
                dropReason = DropReason::BLOCKED;
            }
            // 2. 分發(fā)觸摸事件
            done = dispatchMotionLocked(currentTime, motionEntry, &dropReason, nextWakeupTime);
            break;
        }
        // ...
    }
    // 3. 如果事件被處理，重置一些狀態(tài)，例如 mPendingEvent
    // 返回 true，就表示已經(jīng)處理了事件
    // 事件被丟棄，或者發(fā)送完畢，都會(huì)返回 true
    // 返回 false，表示暫時(shí)不知道如何處理事件，因此線程會(huì)休眠
    // 然后，線程再次被喚醒時(shí)，再來(lái)處理這個(gè)事件
    if (done) {
        if (dropReason != DropReason::NOT_DROPPED) {
            dropInboundEventLocked(*mPendingEvent, dropReason);
        }
        mLastDropReason = dropReason;
        // 重置 mPendingEvent
        releasePendingEventLocked();
        // 立即喚醒，處理下一個(gè)事件
        *nextWakeupTime = LONG_LONG_MIN; // force next poll to wake up immediately
    }
}

bool InputDispatcher::dispatchMotionLocked(nsecs_t currentTime, std::shared_ptr<MotionEntry> entry,
                                           DropReason* dropReason, nsecs_t* nextWakeupTime) {
    if (!entry->dispatchInProgress) {
        entry->dispatchInProgress = true;
    }
    // 1. 觸摸事件有原因需要丟棄，那么不走后面的分發(fā)流程
    if (*dropReason != DropReason::NOT_DROPPED) {
        setInjectionResult(*entry,
                           *dropReason == DropReason::POLICY ? InputEventInjectionResult::SUCCEEDED
                                                             : InputEventInjectionResult::FAILED);
        return true;
    }
    bool isPointerEvent = entry->source & AINPUT_SOURCE_CLASS_POINTER;
    std::vector<InputTarget> inputTargets;
    bool conflictingPointerActions = false;
    InputEventInjectionResult injectionResult;
    if (isPointerEvent) {
        // 尋找觸摸的窗口，窗口保存到 inputTargets
        // 2. 為觸摸事件，尋找觸摸的窗口
        // 觸摸的窗口保存到 inputTargets 中
        injectionResult =
                findTouchedWindowTargetsLocked(currentTime, *entry, inputTargets, nextWakeupTime,
                                               &conflictingPointerActions);
    } else {
        // ...
    }
    if (injectionResult == InputEventInjectionResult::PENDING) {
        // 返回 false，表示暫時(shí)不知道如何處理這個(gè)事件，這會(huì)導(dǎo)致線程休眠
        // 等線程下次被喚醒時(shí)，再來(lái)處理這個(gè)事件
        return false;
    }
    // 走到這里，表示觸摸事件已經(jīng)被處理，因此保存處理的結(jié)果
    // 只要返回的不是 InputEventInjectionResult::PENDING
    // 都表示事件被處理，無(wú)論是權(quán)限拒絕還是失敗，或是成功
    setInjectionResult(*entry, injectionResult);
    if (injectionResult == InputEventInjectionResult::PERMISSION_DENIED) {
        ALOGW("Permission denied, dropping the motion (isPointer=%s)", toString(isPointerEvent));
        return true;
    }
    if (injectionResult != InputEventInjectionResult::SUCCEEDED) {
        CancelationOptions::Mode mode(isPointerEvent
                                              ? CancelationOptions::CANCEL_POINTER_EVENTS
                                              : CancelationOptions::CANCEL_NON_POINTER_EVENTS);
        CancelationOptions options(mode, "input event injection failed");
        synthesizeCancelationEventsForMonitorsLocked(options);
        return true;
    }
    // 走到這里，表示觸摸事件已經(jīng)成功找到觸摸的窗口
    // Add monitor channels from event's or focused display.
    // 3. 觸摸事件找到了觸摸窗口，在分發(fā)給窗口前，保存 global monitor 到 inputTargets 中
    // 開(kāi)發(fā)者選項(xiàng)中的 Show taps 和 Pointer location，利用的 global monitor
    addGlobalMonitoringTargetsLocked(inputTargets, getTargetDisplayId(*entry));
    if (isPointerEvent) {
        // ... 省略 portal window 處理的代碼
    }
    if (conflictingPointerActions) {
        // ...
    }
    // 4. 分發(fā)事件給 inputTargets 中的所有窗口
    dispatchEventLocked(currentTime, entry, inputTargets);
    return true;
}

InputEventInjectionResult InputDispatcher::findTouchedWindowTargetsLocked(
        nsecs_t currentTime, const MotionEntry& entry, std::vector<InputTarget>& inputTargets,
        nsecs_t* nextWakeupTime, bool* outConflictingPointerActions) {
    // ...
    // 6. 對(duì)于非 DOWN 事件，獲取已經(jīng) DOWN 事件保存的 TouchState
    // TouchState 保存了接收 DOWN 事件的窗口
    const TouchState* oldState = nullptr;
    TouchState tempTouchState;
    std::unordered_map<int32_t, TouchState>::iterator oldStateIt =
            mTouchStatesByDisplay.find(displayId);
    if (oldStateIt != mTouchStatesByDisplay.end()) {
        oldState = &(oldStateIt->second);
        tempTouchState.copyFrom(*oldState);
    }
    // ...
    // 第一個(gè)條件 newGesture 表示第一個(gè)手指按下
    // 后面一個(gè)條件，表示當(dāng)前窗口支持 split motion，并且此時(shí)有另外一個(gè)手指按下
    if (newGesture || (isSplit && maskedAction == AMOTION_EVENT_ACTION_POINTER_DOWN)) {
        /* Case 1: New splittable pointer going down, or need target for hover or scroll. */
        // 觸摸點(diǎn)的獲取 x, y 坐標(biāo)
        int32_t x;
        int32_t y;
        int32_t pointerIndex = getMotionEventActionPointerIndex(action);
        if (isFromMouse) {
            // ...
        } else {
            x = int32_t(entry.pointerCoords[pointerIndex].getAxisValue(AMOTION_EVENT_AXIS_X));
            y = int32_t(entry.pointerCoords[pointerIndex].getAxisValue(AMOTION_EVENT_AXIS_Y));
        }
        // 這里檢測(cè)是否是第一個(gè)手指按下
        bool isDown = maskedAction == AMOTION_EVENT_ACTION_DOWN;
        // 1. 對(duì)于 DOWN 事件，根據(jù)觸摸事件的x,y坐標(biāo)，尋找觸摸窗口
        // 參數(shù) addOutsideTargets 表示，只有在第一個(gè)手指按下時(shí)，如果沒(méi)有找到觸摸的窗口，
        // 那么需要保存那些可以接受 OUTSIZE 事件的窗口到 tempTouchState
        newTouchedWindowHandle =
                findTouchedWindowAtLocked(displayId, x, y, &tempTouchState,
                                          isDown /*addOutsideTargets*/, true /*addPortalWindows*/);
        // 省略 ... 處理窗口異常的情況 ...
        // 2. 獲取所有的 getsture monitor
        const std::vector<TouchedMonitor> newGestureMonitors = isDown
                ? selectResponsiveMonitorsLocked(
                          findTouchedGestureMonitorsLocked(displayId, tempTouchState.portalWindows))
                : tempTouchState.gestureMonitors;
        // 既沒(méi)有找到觸摸點(diǎn)所在的窗口，也沒(méi)有找到 gesture monitor，那么此次尋找觸摸窗口的任務(wù)就失敗了
        if (newTouchedWindowHandle == nullptr && newGestureMonitors.empty()) {
            ALOGI("Dropping event because there is no touchable window or gesture monitor at "
                  "(%d, %d) in display %" PRId32 ".",
                  x, y, displayId);
            injectionResult = InputEventInjectionResult::FAILED;
            goto Failed;
        }
        // 走到這里，表示找到了觸摸的窗口，或者找到 gesture monitor
        if (newTouchedWindowHandle != nullptr) {
            // 馬上要保存窗口了，現(xiàn)在獲取窗口的 flag
            int32_t targetFlags = InputTarget::FLAG_FOREGROUND | InputTarget::FLAG_DISPATCH_AS_IS;
            if (isSplit) {
                targetFlags |= InputTarget::FLAG_SPLIT;
            }
            if (isWindowObscuredAtPointLocked(newTouchedWindowHandle, x, y)) {
                targetFlags |= InputTarget::FLAG_WINDOW_IS_OBSCURED;
            } else if (isWindowObscuredLocked(newTouchedWindowHandle)) {
                targetFlags |= InputTarget::FLAG_WINDOW_IS_PARTIALLY_OBSCURED;
            }
            // Update hover state.
            if (maskedAction == AMOTION_EVENT_ACTION_HOVER_EXIT) {
                newHoverWindowHandle = nullptr;
            } else if (isHoverAction) {
                newHoverWindowHandle = newTouchedWindowHandle;
            }
            // Update the temporary touch state.
            // 如果窗口支持 split，那么用 tempTouchState 保存窗口的時(shí)候，要特別保存 pointer id
            BitSet32 pointerIds;
            if (isSplit) {
                uint32_t pointerId = entry.pointerProperties[pointerIndex].id;
                pointerIds.markBit(pointerId);
            }
            // 3. tempTouchState 保存找到的觸摸的窗口
            // 如果是真的找到的觸摸窗口，那么這里就是保存，如果是找到可以接受 OUTSIDE 的窗口，那么這里是更新
            tempTouchState.addOrUpdateWindow(newTouchedWindowHandle, targetFlags, pointerIds);
        } else if (tempTouchState.windows.empty()) {
            // If no window is touched, set split to true. This will allow the next pointer down to
            // be delivered to a new window which supports split touch.
            tempTouchState.split = true;
        }
        if (isDown) {
            // tempTouchState 保存所有的 gesture monitor
            // 4. 第一個(gè)手指按下時(shí)，tempTouchState 保存 gesture monitor
            tempTouchState.addGestureMonitors(newGestureMonitors);
        }
    } else {
        // ...
    }
    if (newHoverWindowHandle != mLastHoverWindowHandle) {
        // ....
    }
    {
        // 權(quán)限檢測(cè) ...
    }
    // 保存接收 AMOTION_EVENT_ACTION_OUTSIDE 的窗口
    if (maskedAction == AMOTION_EVENT_ACTION_DOWN) {
        // ...
    }
    // 第一個(gè)手指按下時(shí)，保存壁紙窗口
    if (maskedAction == AMOTION_EVENT_ACTION_DOWN) { // 
        // ...
    }
    // 走到這里，表示沒(méi)有異常情況了
    injectionResult = InputEventInjectionResult::SUCCEEDED;
    // 5. 把 tempTouchState 保存了觸摸窗口和gesture monitor，保存到 inputTargets 中
    for (const TouchedWindow& touchedWindow : tempTouchState.windows) {
        addWindowTargetLocked(touchedWindow.windowHandle, touchedWindow.targetFlags,
                              touchedWindow.pointerIds, inputTargets);
    }
    for (const TouchedMonitor& touchedMonitor : tempTouchState.gestureMonitors) {
        addMonitoringTargetLocked(touchedMonitor.monitor, touchedMonitor.xOffset,
                                  touchedMonitor.yOffset, inputTargets);
    }
    // Drop the outside or hover touch windows since we will not care about them
    // in the next iteration.
    tempTouchState.filterNonAsIsTouchWindows();
Failed:
    // ...
    // 6. 緩存 tempTouchState
    if (maskedAction != AMOTION_EVENT_ACTION_SCROLL) {
        if (tempTouchState.displayId >= 0) {
            mTouchStatesByDisplay[displayId] = tempTouchState;
        } else {
            mTouchStatesByDisplay.erase(displayId);
        }
    } 
    return injectionResult;
}

// addOutsideTargets 在第一個(gè)手指按下是為 true
// addPortalWindows 值為 true
// ignoreDragWindow 默認(rèn)為 false
sp<InputWindowHandle> InputDispatcher::findTouchedWindowAtLocked(int32_t displayId, int32_t x,
                                                                 int32_t y, TouchState* touchState,
                                                                 bool addOutsideTargets,
                                                                 bool addPortalWindows,
                                                                 bool ignoreDragWindow) {
    if ((addPortalWindows || addOutsideTargets) && touchState == nullptr) {
        LOG_ALWAYS_FATAL(
                "Must provide a valid touch state if adding portal windows or outside targets");
    }
    // Traverse windows from front to back to find touched window.
    // 從前到后，遍歷窗口
    const std::vector<sp<InputWindowHandle>>& windowHandles = getWindowHandlesLocked(displayId);
    for (const sp<InputWindowHandle>& windowHandle : windowHandles) {
        // ignoreDragWindow 默認(rèn)為 false
        if (ignoreDragWindow && haveSameToken(windowHandle, mDragState->dragWindow)) {
            continue;
        }
        // 獲取窗口信息
        const InputWindowInfo* windowInfo = windowHandle->getInfo();
        // 匹配屬于特定屏幕的窗口
        if (windowInfo->displayId == displayId) {
            auto flags = windowInfo->flags;
            // 窗口要可見(jiàn)
            if (windowInfo->visible) {
                // 窗口要可觸摸
                if (!flags.test(InputWindowInfo::Flag::NOT_TOUCHABLE)) {
                    // 檢測(cè)是否為觸摸模型: 可獲取焦點(diǎn)，并且不允許窗口之外的觸摸事件發(fā)送到它后面的窗口
                    bool isTouchModal = !flags.test(InputWindowInfo::Flag::NOT_FOCUSABLE) &&
                            !flags.test(InputWindowInfo::Flag::NOT_TOUCH_MODAL);
                    // 窗口是觸摸模型，或者觸摸的坐標(biāo)點(diǎn)落在窗口上
                    if (isTouchModal || windowInfo->touchableRegionContainsPoint(x, y)) {
                        int32_t portalToDisplayId = windowInfo->portalToDisplayId;
                        // 如果是 portal window
                        if (portalToDisplayId != ADISPLAY_ID_NONE &&
                            portalToDisplayId != displayId) {
                            if (addPortalWindows) {
                                // For the monitoring channels of the display.
                                // touchState 保存 portal window
                                touchState->addPortalWindow(windowHandle);
                            }
                            // 遞歸調(diào)用，獲取 portal display id 下的觸摸窗口
                            return findTouchedWindowAtLocked(portalToDisplayId, x, y, touchState,
                                                             addOutsideTargets, addPortalWindows);
                        }
                        // 不是 portal window，直接返回找到的窗口
                        return windowHandle;
                    }
                }
                // 走到這里，表示沒(méi)有找到觸摸窗口。也就是說(shuō)，既沒(méi)有找到觸摸模型的窗口，也沒(méi)有找到包含觸摸點(diǎn)的窗口
                // 當(dāng)?shù)谝粋€(gè)手指按下是，addOutsideTargets 值為 true
                // NOT_TOUCH_MODAL 和 WATCH_OUTSIDE_TOUCH 一起使用，當(dāng)?shù)谝粋€(gè)手指按下時(shí)，如果落在窗口之外
                // 窗口會(huì)收到 MotionEvent.ACTION_OUTSIDE 事件
                if (addOutsideTargets && flags.test(InputWindowInfo::Flag::WATCH_OUTSIDE_TOUCH)) {
                    touchState->addOrUpdateWindow(windowHandle,
                                                  InputTarget::FLAG_DISPATCH_AS_OUTSIDE,
                                                  BitSet32(0));
                }
            }
        }
    }
    return nullptr;
}

// InputDispatcher 保存觸摸窗口
void InputDispatcher::addWindowTargetLocked(const sp<InputWindowHandle>& windowHandle,
                                            int32_t targetFlags, BitSet32 pointerIds,
                                            std::vector<InputTarget>& inputTargets) {
    std::vector<InputTarget>::iterator it =
            std::find_if(inputTargets.begin(), inputTargets.end(),
                         [&windowHandle](const InputTarget& inputTarget) {
                             return inputTarget.inputChannel->getConnectionToken() ==
                                     windowHandle->getToken();
                         });
    const InputWindowInfo* windowInfo = windowHandle->getInfo();
    // 創(chuàng)建 InputTarget，并保存到參數(shù) inputTargets
    if (it == inputTargets.end()) {
        InputTarget inputTarget;
        std::shared_ptr<InputChannel> inputChannel =
                getInputChannelLocked(windowHandle->getToken());
        if (inputChannel == nullptr) {
            ALOGW("Window %s already unregistered input channel", windowHandle->getName().c_str());
            return;
        }
        inputTarget.inputChannel = inputChannel;
        inputTarget.flags = targetFlags;
        inputTarget.globalScaleFactor = windowInfo->globalScaleFactor;
        inputTarget.displaySize =
                int2(windowHandle->getInfo()->displayWidth, windowHandle->getInfo()->displayHeight);
        inputTargets.push_back(inputTarget);
        it = inputTargets.end() - 1;
    }
    ALOG_ASSERT(it->flags == targetFlags);
    ALOG_ASSERT(it->globalScaleFactor == windowInfo->globalScaleFactor);
    // 保存 InputTarget 后，在保存窗口的坐標(biāo)轉(zhuǎn)換參數(shù)，
    // 這個(gè)參數(shù)可以把顯示屏的坐標(biāo)，轉(zhuǎn)換為窗口的坐標(biāo)
    it->addPointers(pointerIds, windowInfo->transform);
}
// InputDispatcher 保存 gesture monitor
void InputDispatcher::addMonitoringTargetLocked(const Monitor& monitor, float xOffset,
                                                float yOffset,
                                                std::vector<InputTarget>& inputTargets) {
    InputTarget target;
    target.inputChannel = monitor.inputChannel;
    target.flags = InputTarget::FLAG_DISPATCH_AS_IS;
    ui::Transform t;
    t.set(xOffset, yOffset);
    target.setDefaultPointerTransform(t);
    inputTargets.push_back(target);
}