Objective-C里面通过RGB值的方式创建一个UIColor的对象很简单,只需要传递给指定的RGB值就可以了:
+ (UIColor *)colorWithRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue alpha:(CGFloat)alpha
不过这个方法有一个问题,就是这里面的RGB值是用0~1.0的浮点值来表示的,对于常用的0~255的表示方式以及类似FFFFFF的十六进制表示方式并没有对应的方法。我比较喜欢通过Category的方式扩展UIColor,只需要在工程里面添加一个类就行了:
UIColor+CreateMethods.h
//
// UIColor+CreateMethods.h
//
#import <UIKit/UIKit.h>
@interface UIColor (CreateMethods)
// wrapper for [UIColor colorWithRed:green:blue:alpha:]
// values must be in range 0 - 255
+ (UIColor*)colorWith8BitRed:(NSInteger)red green:(NSInteger)green blue:(NSInteger)blue alpha:(CGFloat)alpha;
// Creates color using hex representation
// hex - must be in format: #FF00CC
// alpha - must be in range 0.0 - 1.0
+ (UIColor*)colorWithHex:(NSString*)hex alpha:(CGFloat)alpha;
@end
UIColor+CreateMethods.m
//
// UIColor+CreateMethods.m
//
#import "UIColor+CreateMethods.h"
@implementation UIColor (CreateMethods)
+ (UIColor*)colorWith8BitRed:(NSInteger)red green:(NSInteger)green blue:(NSInteger)blue alpha:(CGFloat)alpha {
return [UIColor colorWithRed:(red/255.0) green:(green/255.0) blue:(blue/255.0) alpha:alpha];
}
+ (UIColor*)colorWithHex:(NSString*)hex alpha:(CGFloat)alpha {
assert(7 == [hex length]);
assert('#' == [hex characterAtIndex:0]);
NSString *redHex = [NSString stringWithFormat:@"0x%@", [hex substringWithRange:NSMakeRange(1, 2)]];
NSString *greenHex = [NSString stringWithFormat:@"0x%@", [hex substringWithRange:NSMakeRange(3, 2)]];
NSString *blueHex = [NSString stringWithFormat:@"0x%@", [hex substringWithRange:NSMakeRange(5, 2)]];
unsigned redInt = 0;
NSScanner *rScanner = [NSScanner scannerWithString:redHex];
[rScanner scanHexInt:&redInt];
unsigned greenInt = 0;
NSScanner *gScanner = [NSScanner scannerWithString:greenHex];
[gScanner scanHexInt:&greenInt];
unsigned blueInt = 0;
NSScanner *bScanner = [NSScanner scannerWithString:blueHex];
[bScanner scanHexInt:&blueInt];
return [UIColor colorWith8BitRed:redInt green:greenInt blue:blueInt alpha:alpha];
}
@end
该方法来自StackOverflow。
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