recyclerview 循环滚动代码

使用RecyclerView实现循环滚动，需要对LayoutManager进行定制。以下是示例代码：

public class LoopLayoutManager extends LinearLayoutManager {
    private boolean isLoop;

    public LoopLayoutManager(Context context, boolean isLoop) {
        super(context);
        this.isLoop = isLoop;
    }

    @Override
    public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int scrolled = super.scrollHorizontallyBy(dx, recycler, state);
        if (isLoop && scrolled == 0) {
            scrolled = scrollLoopHorizontallyBy(dx, recycler, state);
        }
        return scrolled;
    }

    private int scrollLoopHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int width = getWidth();
        if (width <= 0) {
            return 0;
        }
        int totalWidth = getItemCount() * width;
        int scrollOffset = getPaddingLeft() - dx;
        if (scrollOffset < 0) {
            scrollOffset += totalWidth;
        } else if (scrollOffset > totalWidth - width) {
            scrollOffset -= totalWidth;
        }
        offsetChildrenHorizontal(-scrollOffset);
        return dx;
    }

    @Override
    public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int scrolled = super.scrollVerticallyBy(dy, recycler, state);
        if (isLoop && scrolled == 0) {
            scrolled = scrollLoopVerticallyBy(dy, recycler, state);
        }
        return scrolled;
    }

    private int scrollLoopVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int height = getHeight();
        if (height <= 0) {
            return 0;
        }
        int totalHeight = getItemCount() * height;
        int scrollOffset = getPaddingTop() - dy;
        if (scrollOffset < 0) {
            scrollOffset += totalHeight;
        } else if (scrollOffset > totalHeight - height) {
            scrollOffset -= totalHeight;
        }
        offsetChildrenVertical(-scrollOffset);
        return dy;
    }

    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
        super.onLayoutChildren(recycler, state);
        if (isLoop && getItemCount() > 0) {
            scrollToPosition(0);
        }
    }

    @Override
    public void scrollToPosition(int position) {
        if (isLoop && getItemCount() > 0) {
            position = position % getItemCount();
        }
        super.scrollToPosition(position);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        if (isLoop && getItemCount() > 0) {
            position = position % getItemCount();
        }
        super.smoothScrollToPosition(recyclerView, state, position);
    }
}

在使用RecyclerView时，使用上述定制LayoutManager即可实现循环滚动。例如：

RecyclerView recyclerView = findViewById(R.id.recycler_view);
LoopLayoutManager layoutManager = new LoopLayoutManager(this, true);
recyclerView.setLayoutManager(layoutManager);

其中，第二个参数`isLoop`表示是否开启循环滚动。