我如何从十六进制字符串格式创建一个UIColor,如#00FF00?
当前回答
我找到了一个很好的UIColor类别,UIColor+PXExtensions。
用法:UIColor *mycolor = [UIColor pxColorWithHexValue:@"#BADA55"];
而且,为了防止链接到我的要点失败,这里是实际的实现代码:
//
// UIColor+PXExtensions.m
//
#import "UIColor+UIColor_PXExtensions.h"
@implementation UIColor (UIColor_PXExtensions)
+ (UIColor*)pxColorWithHexValue:(NSString*)hexValue
{
//Default
UIColor *defaultResult = [UIColor blackColor];
//Strip prefixed # hash
if ([hexValue hasPrefix:@"#"] && [hexValue length] > 1) {
hexValue = [hexValue substringFromIndex:1];
}
//Determine if 3 or 6 digits
NSUInteger componentLength = 0;
if ([hexValue length] == 3)
{
componentLength = 1;
}
else if ([hexValue length] == 6)
{
componentLength = 2;
}
else
{
return defaultResult;
}
BOOL isValid = YES;
CGFloat components[3];
//Seperate the R,G,B values
for (NSUInteger i = 0; i < 3; i++) {
NSString *component = [hexValue substringWithRange:NSMakeRange(componentLength * i, componentLength)];
if (componentLength == 1) {
component = [component stringByAppendingString:component];
}
NSScanner *scanner = [NSScanner scannerWithString:component];
unsigned int value;
isValid &= [scanner scanHexInt:&value];
components[i] = (CGFloat)value / 256.0f;
}
if (!isValid) {
return defaultResult;
}
return [UIColor colorWithRed:components[0]
green:components[1]
blue:components[2]
alpha:1.0];
}
@end
其他回答
一个伟大的Swift实现(为Xcode 7更新)使用扩展,从各种不同的答案和地方拉到一起。在结尾还需要字符串扩展名。
Use:
let hexColor = UIColor(hex: "#00FF00")
注意:我添加了一个选项,为alpha通道的标准6位十六进制值的末尾添加2个额外的数字(传入值为00-99)。如果这冒犯了你,就把它拿掉。您可以实现它来传递一个可选的alpha参数。
扩展:
extension UIColor {
convenience init(var hex: String) {
var alpha: Float = 100
let hexLength = hex.characters.count
if !(hexLength == 7 || hexLength == 9) {
// A hex must be either 7 or 9 characters (#RRGGBBAA)
print("improper call to 'colorFromHex', hex length must be 7 or 9 chars (#GGRRBBAA)")
self.init(white: 0, alpha: 1)
return
}
if hexLength == 9 {
// Note: this uses String subscripts as given below
alpha = hex[7...8].floatValue
hex = hex[0...6]
}
// Establishing the rgb color
var rgb: UInt32 = 0
let s: NSScanner = NSScanner(string: hex)
// Setting the scan location to ignore the leading `#`
s.scanLocation = 1
// Scanning the int into the rgb colors
s.scanHexInt(&rgb)
// Creating the UIColor from hex int
self.init(
red: CGFloat((rgb & 0xFF0000) >> 16) / 255.0,
green: CGFloat((rgb & 0x00FF00) >> 8) / 255.0,
blue: CGFloat(rgb & 0x0000FF) / 255.0,
alpha: CGFloat(alpha / 100)
)
}
}
字符串扩展: 浮动的来源 下标源
extension String {
/**
Returns the float value of a string
*/
var floatValue: Float {
return (self as NSString).floatValue
}
/**
Subscript to allow for quick String substrings ["Hello"][0...1] = "He"
*/
subscript (r: Range<Int>) -> String {
get {
let start = self.startIndex.advancedBy(r.startIndex)
let end = self.startIndex.advancedBy(r.endIndex - 1)
return self.substringWithRange(start..<end)
}
}
}
除了颜色,我还喜欢保证alpha,所以我自己写类别
+ (UIColor *) colorWithHex:(int)color {
float red = (color & 0xff000000) >> 24;
float green = (color & 0x00ff0000) >> 16;
float blue = (color & 0x0000ff00) >> 8;
float alpha = (color & 0x000000ff);
return [UIColor colorWithRed:red/255.0 green:green/255.0 blue:blue/255.0 alpha:alpha/255.0];
}
像这样很容易使用
[UIColor colorWithHex:0xFF0000FF]; //Red
[UIColor colorWithHex:0x00FF00FF]; //Green
[UIColor colorWithHex:0x00FF00FF]; //Blue
[UIColor colorWithHex:0x0000007F]; //transparent black
一个简明的解决方案:
// Assumes input like "#00FF00" (#RRGGBB).
+ (UIColor *)colorFromHexString:(NSString *)hexString {
unsigned rgbValue = 0;
NSScanner *scanner = [NSScanner scannerWithString:hexString];
[scanner setScanLocation:1]; // bypass '#' character
[scanner scanHexInt:&rgbValue];
return [UIColor colorWithRed:((rgbValue & 0xFF0000) >> 16)/255.0 green:((rgbValue & 0xFF00) >> 8)/255.0 blue:(rgbValue & 0xFF)/255.0 alpha:1.0];
}
我为它创建了一个便利的init:
extension UIColor {
convenience init(hex: String, alpha: CGFloat)
{
let redH = CGFloat(strtoul(hex.substringToIndex(advance(hex.startIndex,2)), nil, 16))
let greenH = CGFloat(strtoul(hex.substringWithRange(Range<String.Index>(start: advance(hex.startIndex, 2), end: advance(hex.startIndex, 4))), nil, 16))
let blueH = CGFloat(strtoul(hex.substringFromIndex(advance(hex.startIndex,4)), nil, 16))
self.init(red: redH/255, green: greenH/255, blue: blueH/255, alpha: alpha)
}
}
然后你可以在项目的任何地方创建一个UIColor,就像这样:
UIColor(hex: "ffe3c8", alpha: 1)
希望这对你有所帮助……
据我所知,没有从十六进制字符串到UIColor(或CGColor)的内置转换。但是,您可以很容易地为此目的编写几个函数—例如,参见iphone开发访问uicolor组件
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