iOS tableView Section圆角方案

给tableView的section设置圆角

- 首先给让cell左右偏移一点的距离，通过重写cell的setframe方法来实现

-(void)setFrame:(CGRect)frame{
    CGFloat margin = 10;
    frame.origin.x = margin;
    frame.size.width = SCREEN_WIDTH - margin*2;
    [super setFrame:frame];
}

• 实现tableView的willDisplayCell方法，给section绘制圆角

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath{
    // 圆角角度
    CGFloat radius = 8.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, 0, 0);
    // 获取每组行数
    NSInteger rowNum = [tableView numberOfRowsInSection:indexPath.section];
    // 贝塞尔曲线
    UIBezierPath *bezierPath = nil;
    
    if (rowNum == 1) {
        // 一组只有一行（四个角全部为圆角）
        bezierPath = [UIBezierPath bezierPathWithRoundedRect:bounds
                                           byRoundingCorners:UIRectCornerAllCorners
                                                 cornerRadii:CGSizeMake(radius, radius)];
    } else {
        if (indexPath.row == 0) {
            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:1 alpha:1.0].CGColor;
    // 添加图层到nomarBgView中
    [nomarBgView.layer insertSublayer:normalLayer atIndex:0];
    nomarBgView.backgroundColor = UIColor.clearColor;
    cell.backgroundView = nomarBgView;
}