RecyclerView返回顶部

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懒得说明了,直接上代码

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public static void scrollToTop(RecyclerView recyclerView) {
    if (null == recyclerView ||
            recyclerView.getChildCount() <= 1 ||
            null == recyclerView.getLayoutManager()) {
        return;
    }
    int firstVisiblePosition = 0;
    int lastVisiblePosition = 0;
    RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
    if (layoutManager instanceof LinearLayoutManager) {
        LinearLayoutManager manager = (LinearLayoutManager) layoutManager;
        manager.getItemCount();
        firstVisiblePosition = manager.findFirstVisibleItemPosition();
        lastVisiblePosition  = manager.findLastVisibleItemPosition();
    } else if (layoutManager instanceof GridLayoutManager) {
        GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
        firstVisiblePosition = gridLayoutManager.findFirstVisibleItemPosition();
        lastVisiblePosition = gridLayoutManager.findLastVisibleItemPosition();
    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
        StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
        firstVisiblePosition = staggeredGridLayoutManager.findFirstVisibleItemPositions(null)[0];
        lastVisiblePosition = staggeredGridLayoutManager.findLastVisibleItemPositions(null)[0];
    }
    int visibleCount = lastVisiblePosition - firstVisiblePosition + 1;
    if (firstVisiblePosition > visibleCount) {
        recyclerView.scrollToPosition(visibleCount);
    }
    recyclerView.smoothScrollToPosition(0);
}