16进制颜色(html颜色值)字符串转为UIColor

   互联网 App 中经常会用到 html 颜色值转换 UIColor，比如：#FF9900、0XFF9900 等颜色字符串，以下方法可以将这些字符串转换为 UIColor 对象。

    + (UIColor *) colorWithHexString: (NSString *) stringToConvert
    {
     NSString *cString = [[stringToConvert stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
     
     // String should be 6 or 8 characters
     if ([cString length] < 6) return DEFAULT_VOID_COLOR;
     
     // strip 0X if it appears
     if ([cString hasPrefix:@"0X"]) cString = [cString substringFromIndex:2];
     f ([cString hasPrefix:@"#"]) cString = [cString substringFromIndex:1];
     if ([cString length] != 6) return DEFAULT_VOID_COLOR;
     // Separate into r, g, b substrings
     NSRange range;
     range.location = 0;
     range.length = 2;
     NSString *rString = [cString substringWithRange:range];
     
     range.location = 2;
     NSString *gString = [cString substringWithRange:range];
     
     range.location = 4;
     NSString *bString = [cString substringWithRange:range];
     
     // Scan values
     unsigned int r, g, b;
     [[NSScanner scannerWithString:rString] scanHexInt:&r];
     [[NSScanner scannerWithString:gString] scanHexInt:&g];
     [[NSScanner scannerWithString:bString] scanHexInt:&b];
     
     return [UIColor colorWithRed:((float) r / 255.0f)
             green:((float) g / 255.0f)
           blue:((float) b / 255.0f)
             alpha:1.0f];
    }