在iOS中將字符串轉換爲十六進制？

Question

我基本上讓用戶在UITextField中輸入一個十六進制值並將其寫入一個字符串以用於顏色選擇（教育目的）。我如何將字符串轉換爲十六進制？

Answer 1

我不知道這是什麼ü希望在您的方案......看看這是有用的或不..

調用第一種方法通過將十六進制串，作爲回報，你也會得到UIColor。

- (UIColor *) colorWithHexString:(NSString *)hexString { 
    NSString *colorString = [[hexString stringByReplacingOccurrencesOfString: @"#" withString: @""] uppercaseString]; 
    CGFloat alpha, red, blue, green; 
    alpha = 1.0f; 
    red = [self colorComponentFrom: colorString start: 0 length: 2]; 
    green = [self colorComponentFrom: colorString start: 2 length: 2]; 
    blue = [self colorComponentFrom: colorString start: 4 length: 2]; 
    return [UIColor colorWithRed: red green: green blue: blue alpha: alpha]; 
} 

- (CGFloat) colorComponentFrom:(NSString *)string start:(NSUInteger)start length:(NSUInteger)length { 
    NSString *substring = [string substringWithRange: NSMakeRange(start, length)]; 
    NSString *fullHex = length == 2 ? substring : [NSString stringWithFormat: @"%@%@", substring, substring]; 
    unsigned hexComponent; 
    [[NSScanner scannerWithString: fullHex] scanHexInt: &hexComponent]; 
    return hexComponent/255.0; 
} 

Answer 2

你好這裏是很好的例子：

+ (UIColor *) colorFromHexString:(NSString *)hexString { 
NSString *cleanString = [hexString stringByReplacingOccurrencesOfString:@"#" withString:@""]; 
if([cleanString length] == 3) { 
    NSString *red = [cleanString substringWithRange:NSMakeRange(0, 1)]; 
    NSString *green = [cleanString substringWithRange:NSMakeRange(1, 1)]; 
    NSString *blue = [cleanString substringWithRange:NSMakeRange(2, 1)]; 
    cleanString = [NSString stringWithFormat:@"ff%1$@%1$@%2$@%2$@%3$@%3$@", red, green, blue]; 
}else if([cleanString length] == 6) { 
    cleanString = [@"ff" stringByAppendingString:cleanString]; 
}else{ 
    //do nothing 
} 

NSLog(@"%@", cleanString); 

unsigned int rgba; 
[[NSScanner scannerWithString:cleanString] scanHexInt:&rgba]; 

CGFloat alpha = ((rgba & 0xFF000000) >> 24)/255.0f; 
CGFloat red = ((rgba & 0x00FF0000) >> 16)/255.0f; 
CGFloat green = ((rgba & 0x0000FF00) >> 8)/255.0f; 
CGFloat blue = (rgba & 0x000000FF)/255.0f; 

return [UIColor colorWithRed:red green:green blue:blue alpha:alpha]; 

}

還可以看到它在我的博客hrupin.com