InputReader::addDeviceLocked(nsecs_t when, int32_t deviceId)
    InputDevice* device = createDeviceLocked(deviceId, controllerNumber, identifier, classes);
        //键盘的Mapper
        if (classes & (INPUT_DEVICE_CLASS_KEYBOARD | INPUT_DEVICE_CLASS_DPAD | INPUT_DEVICE_CLASS_GAMEPAD))
        device->addMapper(new KeyboardInputMapper(device, keyboardSource, keyboardType));
        //多触摸和单触摸的Mapper不同。
        if (classes & INPUT_DEVICE_CLASS_TOUCH_MT) {
            device->addMapper(new MultiTouchInputMapper(device));
        } else if (classes & INPUT_DEVICE_CLASS_TOUCH) {
            device->addMapper(new SingleTouchInputMapper(device));
        }
        //这些Mapper是处理输入事件的核心

InputReader::loopOnce() //InputReader.cpp
    mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);
        processEventsLocked(mEventBuffer, count); //获取到事件后处理
            InputDevice device->process(rawEvents, count); //调用InputDevice的process()来处理
                InputMapper mapper->process(rawEvent); //调用InputMapper的process()来处理。它是个纯虚函数，需要子类必须实现的。
                //这些Mapper就是上面添加的Mapper

MultiTouchInputMapper.process    //InputReader.cpp
    TouchInputMapper::process(rawEvent);
        //由于多点触摸屏中没有Button,Scroll,因此这里不做处理
        mCursorButtonAccumulator.process(rawEvent); //type==EV_KEY才处理
        mCursorScrollAccumulator.process(rawEvent); //type==EV_REL才处理
        mTouchButtonAccumulator.process(rawEvent);  //type==EV_KEY才处理
        //多点触摸的前几个点是不会执行sync的，所有点上报完后input_sync()上报的
        是这个键对，
        if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
            sync(rawEvent->when);
        }
    mMultiTouchMotionAccumulator.process(rawEvent);
        //记录上报的type code pressure等值。

/*上报完所有的触摸点后上报这个type=EV_SYN,code=SYN_REPORT*/
static inline void input_sync(struct input_dev *dev)
{
    input_event(dev, EV_SYN, SYN_REPORT, 0);
}
/*上报完一个触摸点后上报这个type=EV_SYN,code=SYN_MT_REPORT*/
static inline void input_mt_sync(struct input_dev *dev)
{
    input_event(dev, EV_SYN, SYN_MT_REPORT, 0);
}

TouchInputMapper::sync(nsecs_t when) //InputReader.cpp, 注意这个是TouchInputMapper::sync，MultiTouchInputMapper没有重写它。
    MultiTouchInputMapper::syncTouch(nsecs_t when, RawState* outState)
    /*
     * 若驱动不能上报ABS_MT_TRACKING_ID的话，就由软件分配一个id值，
     * 算法就是认为最近的点的id(id是用来判断2点是不是在同一个划痕上)
     * 相同。
     */
    assignPointerIds(last, next)
    processRawTouches(false /*timeout*/);
    TouchInputMapper::processRawTouches
        cookAndDispatch(when);
            cookPointerData();
                dispatchTouches(when, policyFlags);
                    dispatchMotion
                        NotifyMotionArgs args
                        getListener()->notifyMotion(&args);
                            mArgsQueue.push(new NotifyMotionArgs(*args)); //放入队列中