如何查找RecyclerView是否正在向上或向下滚动

Question

我有RecyclerView GridLayoutManager，如果用户向上或向下滚动，我想在类getItemOffsets的方法RecyclerView.ItemDecoration内找到。下面是我在GridDividerDecoration类中的代码，其中我在项目之间绘制边框。

public class GridDividerDecorations extends RecyclerView.ItemDecoration {
private int mInsets;
List<Integer> itemsHeaderPos= new ArrayList<>();
List<Integer> itemsPos= new ArrayList<>();
List<GadgetItem> mList = new ArrayList<>();
int lastItem;
int itemPosition, itemposition2 = 0;

public GridDividerDecorations(Context context,List<GadgetItem> mList ) {
    this.mList = mList;
    mInsets = 6;
}


@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewAdapterPosition();

    if ((parent.getAdapter().getItemViewType(itemPosition) == 0))
        itemsHeaderPos.add(itemPosition);
    if((parent.getAdapter().getItemViewType(itemPosition) != 0))
        itemsPos.add(itemPosition);

    outRect.top = mInsets;

    GridLayoutManager layoutManager = (GridLayoutManager)parent.getLayoutManager();
    if(itemPosition == layoutManager.findLastVisibleItemPosition())
        outRect.right = mInsets;

        if (itemPosition % 2 == 0 && itemsHeaderPos.get(itemsHeaderPos.size() - 1) % 2 == 0) {
            if (parent.getAdapter().getItemViewType(itemPosition) != 0)
                outRect.left = mInsets;
        } else if (itemPosition % 2 == 0 && itemsHeaderPos.get(itemsHeaderPos.size() - 1) % 2 != 0) {
            if (parent.getAdapter().getItemViewType(itemPosition) != 0) {
                outRect.right = mInsets;
            }
        }

}
}

问题是，当我向上滚动时，分隔线被颠倒了，所以如果用户向上滚动我可以恢复我的实现。谢谢！

Answer 1

您可以使用OnScrollChangeListener确定是向上还是向下滚动：

recycler.setOnScrollChangeListener(new View.OnScrollChangeListener() {
    @Override
    public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
        if(oldScrollY - scrollY > 0) {
            // do stuff
        }
        else {
            // do stuff
        }
    }
});