IOS 添加渐变色

CAGradientLayer *gradient = [CAGradientLayer layer];

gradient.frame = CGRectMake(0, 0, contentWeight, 49);

gradient.colors = [NSArray arrayWithObjects:(id)[UIColor colorWithRed:255.0/255.0 green:255.0/255.0 blue:255.0/255.0 alpha:1.0].CGColor,(id)[UIColor colorWithRed:222.0/225.0 green:222.0/225.0 blue:222.0/225.0 alpha:1.0].CGColor,(id)[UIColor colorWithRed:217.0/255.0 green:217.0/255.0 blue:217.0/255.0 alpha:1.0].CGColor,nil];

[scrollV.layer insertSublayer:gradient atIndex:0];