使用的地方：

[_addButton setBackgroundImage:[UIImage imageWithColor:[[UIColor whiteColor] colorWithAlphaComponent:0.f]] forState:UIControlStateDisabled];

UIImage+Theme.m

==============================

+ (UIImage *)imageWithColor:(UIColor *)color

{

    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);

    UIGraphicsBeginImageContext(rect.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [color CGColor]);

    CGContextFillRect(context, rect);

    UIImage *bg = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return bg;

}

使用的地方：

[UIImage imageWithColor:[[UIColor whiteColor] colorWithAlphaComponent:0.f]]