iOS：扩展UIColor，支持十六进制颜色设置

来自转载：http://my.oschina.net/leejan97/blog/307491

摘要： 可以直接使用十六进制设置控件的颜色，而不必通过除以255.0进行转换

#define UIColor Category UIBarButtonItem

新建一个Category，命名为UIColor+Hex，表示UIColor支持十六进制Hex颜色设置。

UIColor+Hex.h文件

#import <UIKit/UIKit.h>

#define RGBA_COLOR(R, G, B, A) [UIColor colorWithRed:((R) / 255.0f) green:((G) / 255.0f) blue:((B) / 255.0f) alpha:A]
#define RGB_COLOR(R, G, B) [UIColor colorWithRed:((R) / 255.0f) green:((G) / 255.0f) blue:((B) / 255.0f) alpha:1.0f]

@interface UIColor (Hex)
+ (UIColor *)colorWithHexString:(NSString *)color;
//从十六进制字符串获取颜色，
//color:支持@“#123456”、 @“0X123456”、 @“123456”三种格式
+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha;
@end

上面的代码在开头是两个宏定义，就是对[UIColor colorWithRed:green:blue:alpha]方法的简化，在UIColor(Hex)中声明两个方法-colorWithHexString和-colorWithHexString:alpha，这个很好理解。

UIColor+Hex.m文件

#import "UIColor+Hex.h"

@implementation UIColor (Hex)

+ (UIColor *)colorWithHexString:(NSString *)color alpha:(CGFloat)alpha
{
    //删除字符串中的空格
    NSString *cString = [[color stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
    // String should be 6 or 8 characters
    if ([cString length] < 6)
    {
        return [UIColor clearColor];
    }
    // strip 0X if it appears
    //如果是0x开头的，那么截取字符串，字符串从索引为2的位置开始，一直到末尾
    if ([cString hasPrefix:@"0X"])
    {
        cString = [cString substringFromIndex:2];
    }
    //如果是#开头的，那么截取字符串，字符串从索引为1的位置开始，一直到末尾
    if ([cString hasPrefix:@"#"])
    {
        cString = [cString substringFromIndex:1];
    }
    if ([cString length] != 6)
    {
        return [UIColor clearColor];
    }

    // Separate into r, g, b substrings
    NSRange range;
    range.location = 0;
    range.length = 2;
    //r
    NSString *rString = [cString substringWithRange:range];
    //g
    range.location = 2;
    NSString *gString = [cString substringWithRange:range];
    //b
    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:alpha];
}

//默认alpha值为1
+ (UIColor *)colorWithHexString:(NSString *)color
{
    return [self colorWithHexString:color alpha:1.0f];
}

@end

这样就扩展了UIColor，支持十六进制颜色设置。下面举个栗子，设置UIButton一些颜色特征，来说明该扩展的使用，

#import "UIColor+Hex.h"
//省略多余的代码

//设置导航栏右侧的BarButtonItem为Button
- (void)setupNavigationItem
{
    UIView *rightView = [[UIView alloc] init];
    rightView.bounds = CGRectMake(0, 0, 52, 44);

    UIButton *rightButton = [UIButton buttonWithType:UIButtonTypeCustom];
    rightButton.frame = CGRectMake(-6, 0, 52, 44);
    rightButton.backgroundImageEdgeInsets = UIEdgeInsetsMake(7, 0, 7, 0);
    //kSetting是国际化的字符串"设置"
    [rightButton setTitle:NVSLocalizedString(@"kSetting", nil) forState:UIControlStateNormal];
    //使用宏定义的RGB_COLOR
//    [rightButton setTitleColor:RGB_COLOR(160, 170, 150) forState:UIControlStateHighlighted];
    //使用UIColor+Hex扩展
    [rightButton setTitleColor:[UIColor colorWithHexString:@"#708c3b"] forState:UIControlStateNormal];
    rightButton.titleLabel.font = [UIFont fontWithName:@"Heiti SC" size:12.f];
    [rightButton setBackgroundImage:[UIImage imageNamed:@"device_setting_bg"]
                           forState:UIControlStateNormal];
    [rightButton setBackgroundImage:[UIImage imageNamed:@"device_setting_bg_press"]
                           forState:UIControlStateHighlighted];
    [rightButton addTarget:self action:@selector(settingBtnPresss:)
          forControlEvents:UIControlEventTouchUpInside];
    [rightView addSubview:rightButton];

    UIBarButtonItem *rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:rightView];
    [self.navigationItem setRightBarButtonItem:rightBarButtonItem animated:YES];

    [rightBarButtonItem release];
    [rightView release];
}

使用差不多就这么简单，总结一下，本篇博客主要有以下几个细节或者说知识点，

（1）宏定义RGB_COLOR和RGBA_COLOR可以设置颜色

（2）UIColor+Hex扩展可以设置颜色

（3）导航栏上面的BarButtonItem怎么设置为Button

（4）Button一些常用和不常用的属性设置