iOS中十六进制的颜色转换UIColor（RGB）

在程序开发中，设计人员给我们的图片可能是像下图一样的。颜色是使用十六进制表示的

此时，我们需要将颜色转换成我们需要的RGB值，这就需要使用像下面的这段代码

调用方法

- (void)viewDidLoad {
    [super viewDidLoad];

    for (int i = 0; i < 5; i++) {
        UIView * view1 = [[UIView alloc] init];
        view1.frame = CGRectMake(100, 100*i + 100, 80, 80);
    switch (i) {
            /*
             case 0、case1、case4:调用方法3 ，方法3可处理以“#和0X开头的16进制字符串”
             case1：调用方法1，其alpha是固定的，只处理十六进制数"0X"开头
             case2：方法2，颜色的alpha可以改变
             */
        case 0:
            view1.backgroundColor = [UIColor colorWithHexString:@"#e5e589"];
            break;
        case 1:
            view1.backgroundColor = [UIColor colorWithHexString:@"0Xe5e589"];
            break;
        case 2:
            view1.backgroundColor = [UIColor colorWithHex:0Xe5e589];
            break;
        case 3:
            view1.backgroundColor = [UIColor colorWithHex:0Xe5e589 alpha:0.5];
            break;
        case 4:
            view1.backgroundColor = [UIColor colorWithHexString:@"#784679"];
            break;
            
        default:
            break;
    }
    
    [self.view addSubview:view1];
  }
}

封装成一个工具类，使用Category添加UIColor的类目

// 颜色转换：iOS中十六进制的颜色转换为UIColor(RGB)
#import <UIKit/UIKit.h>

@interface UIColor (Hex)
// 透明度固定为1，以0x开头的十六进制转换成的颜色
+ (UIColor *)colorWithHex:(long)hexColor;
// 0x开头的十六进制转换成的颜色,透明度可调整
+ (UIColor *)colorWithHex:(long)hexColor alpha:(float)opacity;
// 颜色转换三：iOS中十六进制的颜色（以#开头）转换为UIColor
+ (UIColor *) colorWithHexString: (NSString *)color;

@end
#import "UIColor+Hex.h"

@implementation UIColor (Hex)
// 透明度固定为1，以0x开头的十六进制转换成的颜色
+ (UIColor*) colorWithHex:(long)hexColor;
{
    return [UIColor colorWithHex:hexColor alpha:1.];
}
// 0x开头的十六进制转换成的颜色,透明度可调整
+ (UIColor *)colorWithHex:(long)hexColor alpha:(float)opacity
{
    float red = ((float)((hexColor & 0xFF0000) >> 16))/255.0;
    float green = ((float)((hexColor & 0xFF00) >> 8))/255.0;
    float blue = ((float)(hexColor & 0xFF))/255.0;
    return [UIColor colorWithRed:red green:green blue:blue alpha:opacity];
}
// 颜色转换三：iOS中十六进制的颜色（以#开头）转换为UIColor
+ (UIColor *) colorWithHexString: (NSString *)color
{
    NSString *cString = [[color stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];

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

    // 判断前缀并剪切掉
    if ([cString hasPrefix:@"0X"])
        cString = [cString substringFromIndex:2];
    if ([cString hasPrefix:@"#"])
        cString = [cString substringFromIndex:1];
    if ([cString length] != 6)
        return [UIColor clearColor];

    // 从六位数值中找到RGB对应的位数并转换
    NSRange range;
    range.location = 0;
    range.length = 2;

    //R、G、B
    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];
}
@end