RecyclerView列表項頭部懸浮固定實現

要實現RecyclerView列表項頭部懸浮固定，可以使用RecyclerView的ItemDecoration來實現。下面是一個實現的示例代碼：

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; // 指定哪些位置為頭部
    }

    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);

上面的代碼中，StickyHeaderItemDecoration類實現了RecyclerView的ItemDecoration接口，并在onDrawOver方法中繪制頭部懸浮固定的視圖。在getHeaderView方法中獲取頭部視圖并綁定數據，根據isHeader方法判斷當前位置是否為頭部，然后在onDrawOver方法中繪制頭部視圖。

在Activity或Fragment中，創建StickyHeaderItemDecoration對象并添加到RecyclerView的ItemDecoration中即可實現RecyclerView列表項頭部懸浮固定的效果。