android4.4之触摸点属性（down、move、up）

通常应用程序在处理触摸事件时一般会用到motionevent.getAction()来判断上报的触摸点是ACTION_DOWN、ACTION_MOVE或ACTION_UP，然后做出移动、缩放等处理逻辑。每一个触摸点属性是在哪里定义的呢？是驱动上报就标记了每个点的触摸属性吗？

直接给结论：对于触摸点的属性，在InputReader中的dispatchTouches()函数中定义，而不是驱动给的。

void TouchInputMapper::dispatchTouches(nsecs_t when, uint32_t policyFlags) {
    BitSet32 currentIdBits = mCurrentCookedPointerData.touchingIdBits;
    BitSet32 lastIdBits = mLastCookedPointerData.touchingIdBits;
    int32_t metaState = getContext()->getGlobalMetaState();
    int32_t buttonState = mCurrentButtonState;

    if (currentIdBits == lastIdBits) {
        if (!currentIdBits.isEmpty()) {
            // No pointer id changes so this is a move event.
            // The listener takes care of batching moves so we don't have to deal with that here.
            dispatchMotion(when, policyFlags, mSource,
                    AMOTION_EVENT_ACTION_MOVE, 0, metaState, buttonState,
                    AMOTION_EVENT_EDGE_FLAG_NONE,
                    mCurrentCookedPointerData.pointerProperties,
                    mCurrentCookedPointerData.pointerCoords,
                    mCurrentCookedPointerData.idToIndex,
                    currentIdBits, -1,
                    mOrientedXPrecision, mOrientedYPrecision, mDownTime);
        }
    } else {
        // There may be pointers going up and pointers going down and pointers moving
        // all at the same time.
        BitSet32 upIdBits(lastIdBits.value & ~currentIdBits.value);
        BitSet32 downIdBits(currentIdBits.value & ~lastIdBits.value);
        BitSet32 moveIdBits(lastIdBits.value & currentIdBits.value);
        BitSet32 dispatchedIdBits(lastIdBits.value);

        // Update last coordinates of pointers that have moved so that we observe the new
        // pointer positions at the same time as other pointers that have just gone up.
        bool moveNeeded = updateMovedPointers(
                mCurrentCookedPointerData.pointerProperties,
                mCurrentCookedPointerData.pointerCoords,
                mCurrentCookedPointerData.idToIndex,
                mLastCookedPointerData.pointerProperties,
                mLastCookedPointerData.pointerCoords,
                mLastCookedPointerData.idToIndex,
                moveIdBits);
        if (buttonState != mLastButtonState) {
            moveNeeded = true;
        }

        // Dispatch pointer up events.
        while (!upIdBits.isEmpty()) {
            uint32_t upId = upIdBits.clearFirstMarkedBit();

            dispatchMotion(when, policyFlags, mSource,
                    AMOTION_EVENT_ACTION_POINTER_UP, 0, metaState, buttonState, 0,
                    mLastCookedPointerData.pointerProperties,
                    mLastCookedPointerData.pointerCoords,
                    mLastCookedPointerData.idToIndex,
                    dispatchedIdBits, upId,
                    mOrientedXPrecision, mOrientedYPrecision, mDownTime);
            dispatchedIdBits.clearBit(upId);
        }

        // Dispatch move events if any of the remaining pointers moved from their old locations.
        // Although applications receive new locations as part of individual pointer up
        // events, they do not generally handle them except when presented in a move event.
        if (moveNeeded) {
            ALOG_ASSERT(moveIdBits.value == dispatchedIdBits.value);
            dispatchMotion(when, policyFlags, mSource,
                    AMOTION_EVENT_ACTION_MOVE, 0, metaState, buttonState, 0,
                    mCurrentCookedPointerData.pointerProperties,
                    mCurrentCookedPointerData.pointerCoords,
                    mCurrentCookedPointerData.idToIndex,
                    dispatchedIdBits, -1,
                    mOrientedXPrecision, mOrientedYPrecision, mDownTime);
        }

        // Dispatch pointer down events using the new pointer locations.
        while (!downIdBits.isEmpty()) {
            uint32_t downId = downIdBits.clearFirstMarkedBit();
            dispatchedIdBits.markBit(downId);

            if (dispatchedIdBits.count() == 1) {
                // First pointer is going down.  Set down time.
                mDownTime = when;
            }

            dispatchMotion(when, policyFlags, mSource,
                    AMOTION_EVENT_ACTION_POINTER_DOWN, 0, metaState, buttonState, 0,
                    mCurrentCookedPointerData.pointerProperties,
                    mCurrentCookedPointerData.pointerCoords,
                    mCurrentCookedPointerData.idToIndex,
                    dispatchedIdBits, downId,
                    mOrientedXPrecision, mOrientedYPrecision, mDownTime);
        }
    }
}

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