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Recycleview模仿瑞幸咖啡菜单物品列表

作者:互联网

ItemDecoration


一:手动构造数据格式,如下,返回list

Goods goods1 = new Goods("人气TOP", "正果拿铁1", "Y27", "默认:大/单糖/热");
Goods goods99 = new Goods("人气TOP", "正果拿铁2", "Y27", "默认:大/单糖/热");
Goods goods91 = new Goods("人气TOP", "正果拿铁3", "Y27", "默认:大/单糖/热");
Goods goods2 = new Goods("大师咖啡", "拿铁", "Y27", "默认:大/单糖/热");
Goods goods3 = new Goods("大师咖啡", "香草拿铁", "Y24", "默认:大/单糖/热");
Goods goods4 = new Goods("大师咖啡", "焦糖拿铁", "Y26", "默认:大/半糖/热");
List<Goods> list = new ArrayList<>();

二:书写自己的ItemDecoration

第一个必须预留,当前位置的name和前一个不相等则为预留空间
  @Override
public boolean isParent(int position) {
    if (position == 0) return true;
        if (!list.get(position).getType().equals(list.get(position - 1).getType()))
            return true;
    return false;
}
//是否为当前最后一个item
protected boolean lastOneInGroup(int position) {
        String parentName = mDecorListener.parentName(position);
        String nextGroupName;
        try {
            nextGroupName = mDecorListener.parentName(position + 1);
        } catch (Exception e) {
            nextGroupName = null;
        }
        if (nextGroupName == null) {
            return false;
        }
        return !TextUtils.equals(parentName, nextGroupName);//与下一行的name不一样说明当前是最后一行
    }

由上isParent判断是第一个的返回你要预留的高度大小,否则为不需要空间0
 @Override
  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        int position = parent.getChildAdapterPosition(view);
        if (parent.getLayoutManager() instanceof LinearLayoutManager && mDecorListener.isParent(position)) {
            outRect.top = decorationHeight;
            return;
        }
        outRect.top = 0;
    }
 @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDrawOver(c, parent, state);
        final int itemCount = state.getItemCount(); 全部item的数量
        final int childCount = parent.getChildCount(); 可看见的排除悬停的分割线的个数
        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();
        for (int i = 0; i < childCount; i++) {
            View childView = parent.getChildAt(i);
            int position = parent.getChildAdapterPosition(childView);//就是当前可见每一行的position,从0开始
            //默认第一个就是有个Group
            if (mDecorListener.isParent(position) || i == 0) {//中第一个位置和可见的第一个才有这个悬停
                //绘制悬浮,
                int bottom = Math.max(decorationHeight, (childView.getTop() + parent.getPaddingTop()));
                //决定当前顶部第一个悬浮Group的bottom,拿到item高度和规定高度对比,只是选择一个合适的高度定义分割线
                if (position + 1 < itemCount) {
                    //下一组的第一个View接近头部
                    int viewBottom = childView.getBottom();
                    if (lastOneInGroup(position) && viewBottom < bottom) {
                        bottom = viewBottom;                    //如果这个关掉,会覆盖,顶上去效果失去,其实viewBottom逐渐变为0,这样动态的放置即将消失的悬浮拦,看上去就是下一个悬浮拦顶上来的
                    }
                }
                drawDecoration(c, position, left, right, bottom, parent);
                stickyHeaderPosArray.put(position, bottom);
            } 
        }
    }

    private void drawDecoration(Canvas c, int position, int left, int right, int bottom, RecyclerView parent) {
        c.drawRect(left, bottom - decorationHeight, right, bottom, mGroutPaint);
        Paint.FontMetrics fm = mTextPaint.getFontMetrics();
        //文字竖直居中显示
        float baseLine = bottom - (decorationHeight - (fm.bottom - fm.top)) / 2 - fm.bottom;
        //获取文字宽度
        mSideMargin = Math.abs(mSideMargin);
        c.drawText(mDecorListener.parentName(position), left + mSideMargin, baseLine, mTextPaint);//x轴,baseLine
        Rect rect = new Rect();//为了得到当前text的属性
        mTextPaint.getTextBounds(mDecorListener.parentName(position), 0, mDecorListener.parentName(position).length(), rect);
        //绘制那条横线
        c.drawLine(left + mSideMargin * 2 + rect.width(), baseLine - rect.height() / 2, parent.getWidth() -
                mSideMargin, baseLine - rect.height() / 2, mTextPaint);

    }

完结

标签:瑞幸,菜单,parent,bottom,int,Recycleview,Goods,new,position
来源: https://blog.51cto.com/8912823/2367243