來(lái)源：http://m.itdecent.cn/p/739408a7aae1

給section添加圓角和陰影效果，效果如下：

image.png

全部實(shí)現(xiàn)都在UITableView的willDisplayCell代理方法里：
給每個(gè)section第一個(gè)和最后一個(gè)cell分別添加頂部和底部圓角

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    // 圓角角度
    CGFloat radius = 10.f;
    // 設(shè)置cell 背景色為透明
    cell.backgroundColor = UIColor.clearColor;
    // 創(chuàng)建兩個(gè)layer
    CAShapeLayer *normalLayer = [[CAShapeLayer alloc] init];
    CAShapeLayer *selectLayer = [[CAShapeLayer alloc] init];
    // 獲取顯示區(qū)域大小
    CGRect bounds = CGRectInset(cell.bounds, kScaleX * 20, 0);
    // cell的backgroundView
    UIView *normalBgView = [[UIView alloc] initWithFrame:bounds];
    // 獲取每組行數(shù)
    NSInteger rowNum = [tableView numberOfRowsInSection:indexPath.section];
    // 貝塞爾曲線
    UIBezierPath *bezierPath = nil;
    
    if (rowNum == 1) {
        // 一組只有一行（四個(gè)角全部為圓角）
        bezierPath = [UIBezierPath bezierPathWithRoundedRect:bounds byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(radius, radius)];
        normalBgView.clipsToBounds = NO;
    }else {
        normalBgView.clipsToBounds = YES;
        if (indexPath.row == 0) {
            normalBgView.frame = UIEdgeInsetsInsetRect(bounds, UIEdgeInsetsMake(-5, 0, 0, 0));
            CGRect rect = UIEdgeInsetsInsetRect(bounds, UIEdgeInsetsMake(5, 0, 0, 0));
            // 每組第一行（添加左上和右上的圓角）
            bezierPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerTopRight) cornerRadii:CGSizeMake(radius, radius)];
        }else if (indexPath.row == rowNum - 1) {
            normalBgView.frame = UIEdgeInsetsInsetRect(bounds, UIEdgeInsetsMake(0, 0, -5, 0));
            CGRect rect = UIEdgeInsetsInsetRect(bounds, UIEdgeInsetsMake(0, 0, 5, 0));
            // 每組最后一行（添加左下和右下的圓角）
            bezierPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:(UIRectCornerBottomLeft|UIRectCornerBottomRight) cornerRadii:CGSizeMake(radius, radius)];
        }else {
            // 每組不是首位的行不設(shè)置圓角
            bezierPath = [UIBezierPath bezierPathWithRect:bounds];
        }
    }
    
    // 陰影
    normalLayer.shadowColor = [UIColor blackColor].CGColor;
    normalLayer.shadowOpacity = 0.2;
    normalLayer.shadowOffset = CGSizeMake(0, 0);
    normalLayer.path = bezierPath.CGPath;
    normalLayer.shadowPath = bezierPath.CGPath;
    
    // 把已經(jīng)繪制好的貝塞爾曲線路徑賦值給圖層，然后圖層根據(jù)path進(jìn)行圖像渲染render
    normalLayer.path = bezierPath.CGPath;
    selectLayer.path = bezierPath.CGPath;
    
    // 設(shè)置填充顏色
    normalLayer.fillColor = [UIColor whiteColor].CGColor;
    // 添加圖層到nomarBgView中
    [normalBgView.layer insertSublayer:normalLayer atIndex:0];
    normalBgView.backgroundColor = UIColor.clearColor;
    cell.backgroundView = normalBgView;
    
    // 替換cell點(diǎn)擊效果
    UIView *selectBgView = [[UIView alloc] initWithFrame:bounds];
    selectLayer.fillColor = [UIColor colorWithWhite:0.95 alpha:1.0].CGColor;
    [selectBgView.layer insertSublayer:selectLayer atIndex:0];
    selectBgView.backgroundColor = UIColor.clearColor;
    cell.selectedBackgroundView = selectBgView;
}