使用十六进制色值表示UIColor

假如你有一个值为 @”0A5CEA” (字符串类型的16进制色值) ，可以如下方法创建UIColor对象：

UIColor *color = [UIColor colorwithHexString:@"0A5CEA" alpha:.9];

UIColor Category

然后我们来创建一个UIColor Category，

声明代码 UIColor+fromHex.h ：

@interface UIColor (fromHex)
+ (UIColor *)colorwithHexString:(NSString *)hexStr alpha:(CGFloat)alpha;
@end

implementation代码 UIColor+fromHex.m ：

 1 @implementation UIColor (fromHex)
 2
 3 + (UIColor *)colorwithHexString:(NSString *)hexStr alpha:(CGFloat)alpha;
 4 {
 5   //-----------------------------------------
 6   // Convert hex string to an integer
 7   //-----------------------------------------
 8   unsigned int hexint = 0;
 9
10   // Create scanner
11   NSScanner *scanner = [NSScanner scannerWithString:hexStr];
12
13   // Tell scanner to skip the # character
14   [scanner setCharactersToBeSkipped:[NSCharacterSet
15     characterSetWithCharactersInString:@"#"]];
16   [scanner scanHexInt:&hexint];
17
18   //-----------------------------------------
19   // Create color object, specifying alpha
20   //-----------------------------------------
21   UIColor *color =
22     [UIColor colorWithRed:((CGFloat) ((hexint & 0xFF0000) >> 16))/255
23     green:((CGFloat) ((hexint & 0xFF00) >> 8))/255
24     blue:((CGFloat) (hexint & 0xFF))/255
25     alpha:alpha];
26
27   return color;
28 }
29
30 @end

第8-15行 对 hex value 转换为 unsigned integer.

第20-24行 创建一个 UIColor object 通过位操作 ‘&’ 计算各RGB颜色值， 同时除以255得到float值。

下面示例代码, 包括十六进制值格式“0x0A5CEA” 和@”#0A5CEA” (后者一般用于web开发):

 1 NSString *hexStr1 = @"123ABC";
 2 NSString *hexStr2 = @"#123ABC";
 3 NSString *hexStr3 = @"0x123ABC";
 4
 5 UIColor *color1 = [UIColor colorwithHexString:hexStr1 alpha:.9];
 6 NSLog(@"UIColor: %@", color1);
 7
 8 UIColor *color2 = [UIColor colorwithHexString:hexStr2 alpha:.9];
 9 NSLog(@"UIColor: %@", color2);
10
11 UIColor *color3 = [UIColor colorwithHexString:hexStr3 alpha:.9];
12 NSLog(@"UIColor: %@", color3);

结果如下：

UIColor: UIDeviceRGBColorSpace 0.0705882 0.227451 0.737255 0.9
UIColor: UIDeviceRGBColorSpace 0.0705882 0.227451 0.737255 0.9
UIColor: UIDeviceRGBColorSpace 0.0705882 0.227451 0.737255 0.9

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