UITableViewStyleGrouped下自定义selectedBackgroundView

+(void)roundCorners:(UIRectCorner)corners forView:(UIView *)view {
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds
                                                   byRoundingCorners:corners
                                                         cornerRadii:CGSizeMake(10.0, 10.0)];
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame = view.bounds;
    maskLayer.path = maskPath.CGPath;
    view.layer.mask = maskLayer;
}
+(void)roundCornersForSelectedBackgroundViewForTableView:(UITableView *)tableView cell:(UITableViewCell *)cell indexPath:(NSIndexPath *)indexPath {
    NSUInteger rows = [tableView numberOfRowsInSection:indexPath.section];
    if (rows == 1)
    {
        [[self class] roundCorners:UIRectCornerAllCorners forView:cell.selectedBackgroundView];
    } else if (indexPath.row == 0)
    {
        [[self class] roundCorners:UIRectCornerTopLeft | UIRectCornerTopRight forView:cell.selectedBackgroundView];
    } else if (indexPath.row == rows-1)
    {
        [[self class] roundCorners:UIRectCornerBottomLeft | UIRectCornerBottomRight forView:cell.selectedBackgroundView];
    } else {
        [[self class] roundCorners:0 forView:cell.selectedBackgroundView];
    }
}
+(void)deferredRoundCornersForSelectedBackgroundViewForTableView:(UITableView *)tableView cell:(UITableViewCell *)cell indexPath:(NSIndexPath *)indexPath
{
    int64_t delayInSeconds = 0;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        [[self class] roundCornersForSelectedBackgroundViewForTableView:tableView cell:cell indexPath:indexPath];
    });
}


- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    // cell.selectedBackgroundView.frame is not sized correctly yet, so rounding the corners has to be deferred briefly
    [[self class] deferredRoundCornersForSelectedBackgroundViewForTableView:tableView cell:cell indexPath:indexPath];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString* identifityString = @"cell";
    YQOptionTableViewCell* cell = (YQOptionTableViewCell*)[tableView dequeueReusableCellWithIdentifier:identifityString];
    if(!cell)
    {
        cell = [[[YQOptionTableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:identifityString] autorelease];
        cell.selectedBackgroundView = [[UIView alloc]initWithFrame:cell.frame];
        cell.selectedBackgroundView.backgroundColor = [UIColor redColor];
    
    }