appBarLayout.setExpanded(false, true);//先缩起AppBarLayout

//然后滚动NestedScrollView

scroll.post(new Runnable() {
    @Override
    public void run() {
        scroll1(expandableListView, finalI, finalJ);
    }
});

 public void scroll1(ExpandableListView expandableListView,int groupIndex, int childIndex) {
        int totalHeight = 0;
        int position = 0;
        if(groupIndex==0)
        {

            View group = expandableListView.getExpandableListAdapter().getGroupView(0, true, null, expandableListView);
           //测量高度，这里把子item高度和父item高度视为一样高，不一样高的需要重新测量child的高度
            group.measure(0, 0);
            totalHeight += group.getMeasuredHeight() ;
        }
        else
        {
            for (int i = 0; i < groupIndex; i++) {
                position++;
                View group = expandableListView.getExpandableListAdapter().getGroupView(i, true, null, expandableListView);
               //测量高度

                group.measure(0, 0);
                totalHeight += group.getMeasuredHeight() ;
                if (expandableListView.isGroupExpanded(i)){
                    position = position + expandableListView.getExpandableListAdapter().getChildrenCount(i);
                }
            }
        }
        position++;
        position = position + childIndex;

        scroll.smoothScrollTo(0, position*totalHeight);


    }
参考https://*.com/questions/53474588/scrolltoposition-smoothscrolltoposition-for-recyclerview-under-a-nestedscrollvi
https://blog.csdn.net/weixin_39694016/article/details/117679934