1. NSData转为十六进制字符串

//NSData转为十六进制字符串
-(NSString *)HexStringWithData:(NSData *)data{
    Byte *bytes = (Byte *)[data bytes];
    NSString *hexStr=@"";
    for(int i=0;i<[data length];i++) {
        NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数
        if([newHexStr length]==1){
            hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
        }
        else{
            hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
        }
    }
    hexStr = [hexStr uppercaseString];
    return hexStr;
}

2. 普通字符串转十六进制字符串

//普通字符串转十六进制字符串
- (NSString *)hexStringFromString:(NSString *)string{
    NSData *myD = [string dataUsingEncoding:NSUTF8StringEncoding];
    Byte *bytes = (Byte *)[myD bytes];
    //下面是Byte 转换为16进制。
    NSString *hexStr=@"";
    for(int i=0;i<[myD length];i++)
    {
        NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数
        if([newHexStr length]==1)
            hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
        else
            hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
    }
    return hexStr;
}

3.十六进制字符串转NSData

//十六进制字符串转NSData
- (NSData *)convertHexStrToData:(NSString *)str
{
    if (!str || [str length] == 0) {
        return nil;
    }
    
    NSMutableData *hexData = [[NSMutableData alloc] initWithCapacity:20];
    NSRange range;
    if ([str length] % 2 == 0) {
        range = NSMakeRange(0, 2);
    } else {
        range = NSMakeRange(0, 1);
    }
    for (NSInteger i = range.location; i < [str length]; i += 2) {
        unsigned int anInt;
        NSString *hexCharStr = [str substringWithRange:range];
        NSScanner *scanner = [[NSScanner alloc] initWithString:hexCharStr];
        
        [scanner scanHexInt:&anInt];
        NSData *entity = [[NSData alloc] initWithBytes:&anInt length:1];
        [hexData appendData:entity];
        
        range.location += range.length;
        range.length = 2;
    }
    return hexData;
}