贝塞尔曲线实现section圆角

iOS 13 新增分组圆角,属性UITableViewStyleInsetGrouped

- (UITableView *)tableView{
    if (!_tableView) {
        if (@available(iOS 13.0, *)) {
            _tableView = [[UITableView alloc]initWithFrame:CGRectZero style:UITableViewStyleInsetGrouped];
        } else {
            // Fallback on earlier versions
        }

为了兼容iOS13之前机型，可以使用贝塞尔曲线实现section圆角

- (void)tableView:(UITableView *)tableView willDisplayCell:(nonnull UITableViewCell *)cell forRowAtIndexPath:(nonnull NSIndexPath *)indexPath {
     // 圆角角度
    CGFloat radius = 10.f;
    // 设置cell 背景色为透明
    cell.backgroundColor = UIColor.clearColor;
    // 创建两个layer
    CAShapeLayer *normalLayer = [[CAShapeLayer alloc] init];
    CAShapeLayer *selectLayer = [[CAShapeLayer alloc] init];
    // 获取显示区域大小
    CGRect bounds = CGRectInset(cell.bounds, 15, 0);

    // 获取每组行数
    NSInteger rowNum = [tableView numberOfRowsInSection:indexPath.section];
    // 贝塞尔曲线
    UIBezierPath *bezierPath = nil;
    if (rowNum == 1) {
        bezierPath = [UIBezierPath bezierPathWithRoundedRect:bounds byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(radius, radius)];
    }else{
        if (indexPath.row == 0) {
            // 每组第一行（添加左上和右上的圆角）
            bezierPath = [UIBezierPath bezierPathWithRoundedRect:bounds byRoundingCorners:UIRectCornerTopLeft|UIRectCornerTopRight cornerRadii:CGSizeMake(radius, radius)];
        }else if (indexPath.row == rowNum - 1){
            // 每组最后一行（添加左下和右下的圆角）
            bezierPath = [UIBezierPath bezierPathWithRoundedRect:bounds byRoundingCorners:UIRectCornerBottomLeft|UIRectCornerBottomRight cornerRadii:CGSizeMake(radius, radius)];
        }else{
            // 每组不是首位的行不设置圆角
            bezierPath = [UIBezierPath bezierPathWithRect:bounds];
        }
    }
    // 把已经绘制好的贝塞尔曲线路径赋值给图层，然后图层根据path进行图像渲染render
     normalLayer.path = bezierPath.CGPath;
     selectLayer.path = bezierPath.CGPath;
        
     UIView *nomarBgView = [[UIView alloc] initWithFrame:bounds];
     // 设置填充颜色
//         normalLayer.fillColor = [UIColor colorWithWhite:0.95 alpha:1.0].CGColor;
     normalLayer.fillColor = [[UIColor whiteColor] CGColor];
     // 添加图层到nomarBgView中
     [nomarBgView.layer insertSublayer:normalLayer atIndex:0];
     nomarBgView.backgroundColor = UIColor.clearColor;
//         nomarBgView.backgroundColor = UIColor.whiteColor;
     cell.backgroundView = nomarBgView;
    //此时圆角显示就完成了，但是如果没有取消cell的点击效果，还是会出现一个灰色的长方形的形状，再用上面创建的selectLayer给cell添加一个selectedBackgroundView
     UIView *selectBgView = [[UIView alloc] initWithFrame:bounds];
     selectLayer.fillColor = [[UIColor whiteColor] CGColor];
     [selectBgView.layer insertSublayer:selectLayer atIndex:0];
     selectBgView.backgroundColor = UIColor.clearColor;
     cell.selectedBackgroundView = selectBgView;
}

效果如下：