android RecyclerView smoothScrollToPosition 每次都能滚动到顶部

直接使用 smoothScrollToPosition(position) 时，如果要定位的数据在集合下半部分，则滚动结束后，需要显示的数据是在手机界面地步

可以使用 ((LinearLayoutManager) ((RecyclerView)getView(R.id.rv)).getLayoutManager()).scrollToPositionWithOffset(position, 0) 达到每次滚动结束，数据都是在顶部显示，但是数据不是平滑滚动的。

如果要实现不论哪种情况，都能让数据平滑滚动到顶部显示，需要重写 LinearLayoutManager

1，覆写 LinearSmoothScroller

public class TopLinearSmoothScroller extends LinearSmoothScroller {
    public TopLinearSmoothScroller(Context context) {
        super(context);
    }

    @Override
    public int getVerticalSnapPreference() {
        return SNAP_TO_START;
    }
}

2，重写 recyclerview.LinearLayoutManager 的 smoothScrollToPosition 方法

TopLinearSmoothScroller scroller = new TopLinearSmoothScroller(rv.getContext());
LinearLayoutManager layoutManager = new LinearLayoutManager(context) {
    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        super.smoothScrollToPosition(recyclerView, state, position);
        scroller.setTargetPosition(position);
        startSmoothScroll(scroller);
    }
};
rv.setLayoutManager(layoutManager);

3，最后调用 smoothScrollToPosition 即可

rv.smoothScrollToPosition(position);