16进制颜色(html颜色值)字符串转为UIColor

互联应用经常会用到html颜色值转换UIColor，比如：#FF9900,0XFF9900等颜色字符串，以下方法可以将这些字符串转换为 UIColor对象。

//#009900
+(UIColor *) colorWithHexString: (NSString *) stringToConvert
{
	NSString *cString = [[stringToConvert stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
	
	// String should be 6 or 8 characters
	if ([cString length] < 6) return [UIColor blackColor];
	
	// strip 0X if it appears
	if ([cString hasPrefix:@"0X"]) cString = [cString substringFromIndex:2];
	if ([cString hasPrefix:@"#"]) cString = [cString substringFromIndex:1];
	
	if ([cString length] != 6) return [UIColor blackColor];
	
	// Separate into r, g, b substrings
	NSRange range;
	range.location = 0;
	range.length = 2;
	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];
}