一、先了解什么是Hex色值

简单来说就是用十六机制来表示三原色，三原色不同强度组合出不同颜色；
详见：Hex色值是什么（含透明度）

二、代码实现

iOS不如 Kotlin 有API可直接支持HEX赋值，得自己写个扩展方法

普通无透明度代码如下：

    // 示例NSString *hexStr = @"#FFFFFF";if ([hexStr hasPrefix:@"#"]) {hexStr = [cString substringFromIndex:1];}// 解析RGB值NSUInteger red = 0, green = 0, blue = 0;[[NSScanner scannerWithString:cString] scanHexInt:&red];[[NSScanner scannerWithString:[cString substringWithRange:NSMakeRange(2, 2)]] scanHexInt:&green];[[NSScanner scannerWithString:[cString substringWithRange:NSMakeRange(4, 2)]] scanHexInt:&blue];// 将RGB值转换为CGFloat并创建UIColorCGFloat redFloat = (CGFloat)red / 255.0;CGFloat greenFloat = (CGFloat)green / 255.0;CGFloat blueFloat = (CGFloat)blue / 255.0;return [UIColor colorWithRed:redFloat green:greenFloat blue:blueFloat alpha:1.0];

带透明度的代码如下（注意此处解析顺序是RGBA，如仿Kotlin可改为ARGB）：

    // 示例NSString *hexStr = @"#FFFFFFFF";if ([hexStr hasPrefix:@"#"]) {hexStr = [cString substringFromIndex:1];}// 解析RGBA值NSUInteger red = 0, green = 0, blue = 0, alpha = 0;[[NSScanner scannerWithString:cString] scanHexInt:&red];[[NSScanner scannerWithString:[cString substringWithRange:NSMakeRange(2, 2)]] scanHexInt:&green];[[NSScanner scannerWithString:[cString substringWithRange:NSMakeRange(4, 2)]] scanHexInt:&blue];[[NSScanner scannerWithString:[cString substringWithRange:NSMakeRange(6, 2)]] scanHexInt:&alpha];// 将RGBA值转换为CGFloat并创建UIColorCGFloat redFloat = (CGFloat)red / 255.0;CGFloat greenFloat = (CGFloat)green / 255.0;CGFloat blueFloat = (CGFloat)blue / 255.0;CGFloat alphaFloat = (CGFloat)alpha / 255.0;return [UIColor colorWithRed:redFloat green:greenFloat blue:blueFloat alpha:alphaFloat];