调用smoothScrollPosition滚动指定位置，会出现回滚到原来位置

[CTSN]

你好，我用的平板横屏调试demo，出现这个问题。
我debug看了下，
位置0->位置1,正常调用smoothScrollToPosition
位置1->位置2,调用smoothScrollToPosition同时会调用scrollHorizontallyBy，导致mOffsetAll重新计算，导致滚动失败。
我尝试着在scrollHorizontallyBy 和 fixOffsetWhenFinishScroll方法里加个判断，return出去不触发，恢复正常使用。具体原因分析不出来。
我的修改：
` @OverRide
public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler,
RecyclerView.State state) {
if (isSmoothScroll){
Log.e("isSmoothScroll" , "return");
return 0;
}
if (mAnimation != null && mAnimation.isRunning()) mAnimation.cancel();
int travel = dx;
if (!mIsLoop) { //非循环模式，限制滚动位置
if (dx + mOffsetAll < 0) {
travel = -mOffsetAll;
} else if (dx + mOffsetAll > getMaxOffset()){
travel = (int) (getMaxOffset() - mOffsetAll);
}
}
mOffsetAll += travel; //累计偏移量
layoutItems(recycler, state, dx > 0 ? SCROLL_TO_LEFT : SCROLL_TO_RIGHT);
return travel;
}
/**
* 修正停止滚动后，Item滚动到中间位置
/
private void fixOffsetWhenFinishScroll() {
if (isSmoothScroll){
Log.e("smoothScroll","return fixOffsetWhenFinishScroll");
return;
}
int scrollN = (int) (mOffsetAll * 1.0f / getIntervalDistance());
float moreDx = (mOffsetAll % getIntervalDistance());
double judgeDistance = getIntervalDistance() * 0.5;
if (Math.abs(moreDx) > judgeDistance) {
if (moreDx > 0) scrollN ++;
else scrollN --;
}
int finalOffset = (int) (scrollN * getIntervalDistance());
startScroll(mOffsetAll, finalOffset);
mSelectPosition = Math.abs(Math.round (finalOffset * 1.0f / getIntervalDistance())) % getItemCount();
}
/*
* 滚动到指定X轴位置
* @param from X轴方向起始点的偏移量
* @param to X轴方向终点的偏移量
*/
private isSmoothScroll = false;
private void startScroll(int from, int to) {
if (mAnimation != null && mAnimation.isRunning()) {
mAnimation.cancel();
}
final int direction = from < to ? SCROLL_TO_LEFT : SCROLL_TO_RIGHT;
mAnimation = ValueAnimator.ofFloat(from, to);
mAnimation.setDuration(500);
mAnimation.setInterpolator(new DecelerateInterpolator());
mAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@OverRide
public void onAnimationUpdate(ValueAnimator animation) {
mOffsetAll = Math.round((float) animation.getAnimatedValue());
layoutItems(mRecycle, mState, direction);
}
});
mAnimation.addListener(new Animator.AnimatorListener() {
@OverRide
public void onAnimationStart(Animator animation) {
}

        @Override
        public void onAnimationEnd(Animator animation) {
            onSelectedCallBack();
            isSmoothScroll = false;
        }

        @Override
        public void onAnimationCancel(Animator animation) {

        }

        @Override
        public void onAnimationRepeat(Animator animation) {

        }
    });
    mAnimation.start();
}

@OverRide
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
// TODO 循环模式暂不支持平滑滚动

    if (mIsLoop) return;
    int finalOffset = calculateOffsetForPosition(position);
    if (mRecycle == null || mState == null) {//如果RecyclerView还没初始化完，先记录下要滚动的位置
        mSelectPosition = position;
    } else {
        startScroll(mOffsetAll, finalOffset);
        isSmoothScroll = true;
    }
}

`

[lxb89]

请问，如何控制滑动速度，无论慢滑还是快滑都只滑动一个item,而不是将数据集全部滑动一遍