iOS常用方法——十六进制颜色值转换为UIColor

• 字符串十六进制颜色值转换为UIColor：

/**
 16进制颜色转换为UIColor

 @param hexColor 16进制字符串（可以以0x开头，可以以#开头，也可以就是6位的16进制）
 @param opacity 透明度
 @return 16进制字符串对应的颜色
 */
+(UIColor *)colorWithHexString:(NSString *)hexColor alpha:(float)opacity{
    NSString * cString = [[hexColor stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];

    // String should be 6 or 8 characters
    if ([cString length] < 6) return [UIColor blackColor];

    // strip 0X if it appears
    if ([cString hasPrefix:@"0X"]) cString = [cString substringFromIndex:2];
    if ([cString hasPrefix:@"#"]) cString = [cString substringFromIndex:1];

    if ([cString length] != 6) return [UIColor blackColor];

    // 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:opacity];
}

• 十六进制数值转换为UIColor：

+(UIColor*)colorWithRGB:(NSUInteger)hex
                  alpha:(CGFloat)alpha
{
    float r, g, b, a;
    a = alpha;
    b = hex & 0x0000FF;
    hex = hex >> 8;
    g = hex & 0x0000FF;
    hex = hex >> 8;
    r = hex;

    return [UIColor colorWithRed:r/255.0f 
                           green:g/255.0f 
                           blue:b/255.0f 
                           alpha:a];
}

这两个方法建议以类方法写在UIColor的分类中，调用示例：

//字符串十六进制颜色值转换为UIColor
self.view.backgroundColor = [UIColor colorWithHexString:@"000000" alpha:0.4];
//十六进制数值转换为UIColor
self.view.backgroundColor = [UIColor colorWithRGB:0x242424 alpha:0.7];