一张图带你掌握Android Q上InputDispatcher事件分发流程(系统层)

frameworks\native\services\inputflinger\dispatcher\InputDispatcher.cpp
frameworks\native\services\inputflinger\dispatcher\InputDispatcher.h

frameworks\native\include\android\input.h
frameworks\native\services\inputflinger\dispatcher\InputState.cpp
frameworks\native\services\inputflinger\dispatcher\InputState.h
frameworks\native\libs\input\InputTransport.cpp

sourcecode\frameworks\base\core\jni\android_view_InputEventReceiver.cpp
sourcecode\frameworks\base\core\java\android\view\InputEventReceiver.java
sourcecode\frameworks\base\core\java\android\view\ViewRootImpl.java
sourcecode\frameworks\base\core\java\android\view\View.java
frameworks\base\core\java\android\view\ViewGroup.java

void InputDispatcher::dispatchOnce() {
    nsecs_t nextWakeupTime = LONG_LONG_MAX;
    { // acquire lock
        std::scoped_lock _l(mLock);
        mDispatcherIsAlive.notify_all();

        // Run a dispatch loop if there are no pending commands.
        // The dispatch loop might enqueue commands to run afterwards.
        //判断是否有命令，此处的命令是在事件分发的过程中产生的，刷新设备，丢弃事件等等，被封装的命令对象
        if (!haveCommandsLocked()) {
            //此处进行事件分发
            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()) {//执行命令并将下一次唤醒时间设为c++中的最小值
            nextWakeupTime = LONG_LONG_MIN;
        }
    } // release lock

    // Wait for callback or timeout or wake.  (make sure we round up, not down)
    nsecs_t currentTime = now();//计算唤醒时间
    int timeoutMillis = toMillisecondTimeoutDelay(currentTime, nextWakeupTime);
    mLooper->pollOnce(timeoutMillis);//进行下一次循环或者进入休眠
}

bool InputDispatcher::haveCommandsLocked() const {
    //判断命令队列是否为null,里面存储的是CommandEntry实体
    return !mCommandQueue.isEmpty();
}

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

    do {
        //取出队头的命令开始执行
        CommandEntry* commandEntry = mCommandQueue.dequeueAtHead();

        Command command = commandEntry->command;
        (this->*command)(commandEntry); // commands are implicitly 'LockedInterruptible'

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

 

void InputDispatcher::resetKeyRepeatLocked() {
    if (mKeyRepeatState.lastKeyEntry) {
        mKeyRepeatState.lastKeyEntry->release();
        mKeyRepeatState.lastKeyEntry = nullptr;
    }
}

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.
    //判断事件分发是否允许，也就是在未开机、IMS未成功启动、关机等状态下是不可用的，默认值是false
    if (!mDispatchEnabled) {
        resetKeyRepeatLocked();//重置重复按键次数
    }

    // If dispatching is frozen, do not process timeouts or try to deliver any new events.
    //判断分发线程是否被冻结，是否可以配发，默认值是false
    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.
    //判断此处是不是正在切换应用，以便在home和endcall按键到来时，及时丢弃之前的事件，而直接响应特殊键
    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) {//mPendingEvent是即将要被配发的事件，此处是判断是否正在配发事件
        if (mInboundQueue.isEmpty()) {//判断配发事件队列
            if (isAppSwitchDue) {
                // The inbound queue is empty so the app switch key we were waiting
                // for will never arrive.  Stop waiting for it.
                //如果队列是null。那么要等到的home或者挂机键永远不会到来，需要重置
                resetPendingAppSwitchLocked(false);
                isAppSwitchDue = false;
            }

            // Synthesize a key repeat if appropriate.
            //对于某些设备，需要补发按下的重复事件
            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.
            //如果正在配发的事件为null，那么就从配发队列中取出一个，开始配发
            mPendingEvent = mInboundQueue.dequeueAtHead();
            traceInboundQueueLengthLocked();
        }

        // Poke user activity for this event.
        if (mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER) {//判断该事件是不是配发给应用程序的，如果有该标记说明就是
            pokeUserActivityLocked(mPendingEvent);
        }

        // Get ready to dispatch the event.
        //重置此次事件分发的ANR超时时间，如果超过5秒，就会产生ANR
        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 != nullptr);
    bool done = false;
    DropReason dropReason = DROP_REASON_NOT_DROPPED;//默认事件是不丢弃
    if (!(mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER)) {
        dropReason = DROP_REASON_POLICY;//丢弃原因是因为窗口的策略
    } else if (!mDispatchEnabled) {
        dropReason = DROP_REASON_DISABLED;//配发被禁用被丢弃
    }

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

    switch (mPendingEvent->type) {
        case EventEntry::TYPE_CONFIGURATION_CHANGED: {
            ConfigurationChangedEntry* typedEntry =
                    static_cast<ConfigurationChangedEntry*>(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<DeviceResetEntry*>(mPendingEvent);
            done = dispatchDeviceResetLocked(currentTime, typedEntry);
            dropReason = DROP_REASON_NOT_DROPPED; // device resets are never dropped
            break;
        }

        case EventEntry::TYPE_KEY: {
            KeyEntry* typedEntry = static_cast<KeyEntry*>(mPendingEvent);
            if (isAppSwitchDue) {
                if (isAppSwitchKeyEvent(typedEntry)) {
                    resetPendingAppSwitchLocked(true);
                    isAppSwitchDue = false;
                } else if (dropReason == DROP_REASON_NOT_DROPPED) {
                    dropReason = DROP_REASON_APP_SWITCH;
                }
            }
            if (dropReason == DROP_REASON_NOT_DROPPED && isStaleEvent(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<MotionEntry*>(mPendingEvent);
            if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) {
                dropReason = DROP_REASON_APP_SWITCH;
            }
            if (dropReason == DROP_REASON_NOT_DROPPED && isStaleEvent(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);//从配发队列里面丢弃事件
        }
        mLastDropReason = dropReason;

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

bool InputDispatcher::dispatchMotionLocked(nsecs_t currentTime, MotionEntry* entry,
                                           DropReason* dropReason, nsecs_t* nextWakeupTime) {
    ATRACE_CALL();
    // Preprocessing.
    if (!entry->dispatchInProgress) {//设置当前事件的配发进度
        entry->dispatchInProgress = true;

        logOutboundMotionDetails("dispatchMotion - ", entry);//打印出派发事件的详情
    }

    // Clean up if dropping the event.
    if (*dropReason != DROP_REASON_NOT_DROPPED) {//如果是丢弃事件则直接设置派发结果
        setInjectionResult(entry,
                           *dropReason == DROP_REASON_POLICY ? INPUT_EVENT_INJECTION_SUCCEEDED
                                                             : INPUT_EVENT_INJECTION_FAILED);
        return true;
    }
   //判断是不是点事件
    bool isPointerEvent = entry->source & AINPUT_SOURCE_CLASS_POINTER;

    // Identify targets.
    std::vector<InputTarget> inputTargets;//派发的窗口集合

    bool conflictingPointerActions = false;
    int32_t injectionResult;
    if (isPointerEvent) {//是点事件，即就是触摸屏事件，一般情况下都是触摸屏事件
        // Pointer event.  (eg. touchscreen)
        injectionResult =
                findTouchedWindowTargetsLocked(currentTime, entry, inputTargets, nextWakeupTime,
                                               &conflictingPointerActions);
    } else {//轨迹球事件
        // Non touch event.  (eg. trackball)
        injectionResult =
                findFocusedWindowTargetsLocked(currentTime, entry, inputTargets, nextWakeupTime);
    }
    if (injectionResult == INPUT_EVENT_INJECTION_PENDING) {
        return false;
    }

    setInjectionResult(entry, injectionResult);
    if (injectionResult != INPUT_EVENT_INJECTION_SUCCEEDED) {
        if (injectionResult != INPUT_EVENT_INJECTION_PERMISSION_DENIED) {
            CancelationOptions::Mode mode(isPointerEvent
                                                  ? CancelationOptions::CANCEL_POINTER_EVENTS
                                                  : CancelationOptions::CANCEL_NON_POINTER_EVENTS);
            CancelationOptions options(mode, "input event injection failed");
            synthesizeCancelationEventsForMonitorsLocked(options);
        }
        return true;
    }

    // Add monitor channels from event's or focused display.
    addGlobalMonitoringTargetsLocked(inputTargets, getTargetDisplayId(entry));

    if (isPointerEvent) {
        ssize_t stateIndex = mTouchStatesByDisplay.indexOfKey(entry->displayId);
        if (stateIndex >= 0) {
            const TouchState& state = mTouchStatesByDisplay.valueAt(stateIndex);
            if (!state.portalWindows.empty()) {
                // The event has gone through these portal windows, so we add monitoring targets of
                // the corresponding displays as well.
                for (size_t i = 0; i < state.portalWindows.size(); i++) {
                    const InputWindowInfo* windowInfo = state.portalWindows[i]->getInfo();
                    addGlobalMonitoringTargetsLocked(inputTargets, windowInfo->portalToDisplayId,
                                                     -windowInfo->frameLeft, -windowInfo->frameTop);
                }
            }
        }
    }

    // Dispatch the motion.
    //指针冲突，此处可能由于触摸