RecyclerView列表项头部悬浮固定实现

要实现RecyclerView列表项头部悬浮固定，可以使用RecyclerView的ItemDecoration来实现。下面是一个实现的示例代码：

public class StickyHeaderItemDecoration extends RecyclerView.ItemDecoration {
    private static final int HEADER_VIEW_TYPE = 1;

    private LayoutInflater mLayoutInflater;
    private Context mContext;
    private int mHeaderLayoutId;
    private int mHeaderTextViewId;
    private SparseArray<View> mHeaderViews;

    public StickyHeaderItemDecoration(Context context, int headerLayoutId, int headerTextViewId) {
        mLayoutInflater = LayoutInflater.from(context);
        mContext = context;
        mHeaderLayoutId = headerLayoutId;
        mHeaderTextViewId = headerTextViewId;
        mHeaderViews = new SparseArray<>();
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDrawOver(c, parent, state);

        int childCount = parent.getChildCount();
        if (childCount == 0) {
            return;
        }

        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            int position = parent.getChildAdapterPosition(child);

            if (isHeader(position)) {
                View headerView = getHeaderView(parent, position);
                drawHeader(parent, c, headerView);
            }
        }
    }

    private View getHeaderView(RecyclerView parent, int position) {
        int headerPosition = getHeaderPositionForItem(position);
        int layoutResId = getHeaderLayout(headerPosition);
        View headerView = mHeaderViews.get(headerPosition);

        if (headerView == null) {
            headerView = mLayoutInflater.inflate(layoutResId, parent, false);
            mHeaderViews.put(headerPosition, headerView);
        }

        bindHeaderView(headerView, headerPosition);
        return headerView;
    }

    private void bindHeaderView(View headerView, int position) {
        TextView textView = headerView.findViewById(mHeaderTextViewId);
        textView.setText("Header " + position);
    }

    private boolean isHeader(int position) {
        return position == 0 || position == 5 || position == 10; // 指定哪些位置为头部
    }

    private int getHeaderPositionForItem(int position) {
        return position - position / 6;
    }

    private int getHeaderLayout(int headerPosition) {
        return mHeaderLayoutId;
    }

    private void drawHeader(RecyclerView parent, Canvas c, View headerView) {
        c.save();
        c.translate(0, parent.getPaddingTop());
        headerView.draw(c);
        c.restore();
    }
}

在Activity或Fragment中使用StickyHeaderItemDecoration：

StickyHeaderItemDecoration itemDecoration = new StickyHeaderItemDecoration(this, R.layout.layout_header, R.id.tv_header);
recyclerView.addItemDecoration(itemDecoration);

上面的代码中，StickyHeaderItemDecoration类实现了RecyclerView的ItemDecoration接口，并在onDrawOver方法中绘制头部悬浮固定的视图。在getHeaderView方法中获取头部视图并绑定数据，根据isHeader方法判断当前位置是否为头部，然后在onDrawOver方法中绘制头部视图。

在Activity或Fragment中，创建StickyHeaderItemDecoration对象并添加到RecyclerView的ItemDecoration中即可实现RecyclerView列表项头部悬浮固定的效果。