ios - 如何使用 CoreNFC 将 NFC 标签有效负载转换为 URL？

Question

我正在尝试编写一个函数，用于将 NFC 标签有效负载数据转换为 URL 以在 safari 中打开它，但由于某种原因它没有打开，因为它无法将其转换为 URL。我的代码在这里:

 func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
    var result = ""
      for payload in messages[0].records{
          print("-> \(payload)") //Prints the Entire NFC Payload on the Tag.
        result += String.init(data: payload.payload, encoding: .utf16) ?? "Format not supported"
      }
      DispatchQueue.main.async {
        guard let url = URL(string: result) else { return }
        UIApplication.shared.open(url)

      }
}

Answer 1

您需要解码有效载荷，因为它按照 NFC 论坛技术规范中的描述进行编码(例如 NFCForum-TS-NDEF_1.0.pdf，在可能的地方抓取它，但在“白色方向” - 本文档需要被购买)
NDEF 是复杂的格式，为了正确解码，您需要遵守所有功能(无需实现所有功能，但您需要准备好理解有效载荷中出现的所有数据)。
简而言之，对于 URL 类型的解码，您需要对两种类型的有效负载使用react(我的代码在 Objective-C 中，但可以用 Swift 重写):

NSDictionary *urlData; // <- Desired URL placed here
NSString *payloadType = [[NSString alloc] initWithData:payload.type encoding:NSUTF8StringEncoding];
if ([@"Sp" isEqualToString:payloadType]) {
    urlData = [NDEFProcessor parseSmartPoster:payload.payload];
} else if ([@"U" isEqualToString:payloadType]) {
    urlData = [NDEFProcessor parseUriPrimitive:payload.payload];
}

在哪里 NDEFProcessor功能是:

+ (NSString *) uriPrefixForType: (uint8_t) type {
    switch (type) {
        default: return @"";
        case 0x01: return @"http://www.";
        case 0x02: return @"https://www.";
        case 0x03: return @"http://";
        case 0x04: return @"https://";
        case 0x05: return @"tel:";
        case 0x06: return @"mailto:";
    }
}
+ (NSDictionary *) parseUriPrimitive:(NSData *) payload {
    NSMutableDictionary *result = [[NSMutableDictionary alloc] init];
    int schemeType = ((uint8_t *) payload.bytes) [0];
    NSString *uriRaw = [[NSString alloc] initWithBytes:payload.bytes  + 1 length:payload.length - 1 encoding:NSUTF8StringEncoding];
    NSString *proto = [NDEFProcessor uriPrefixForType:schemeType];
    [result setObject: proto
            forKey: @"PROTO"];
    [result setObject: uriRaw
            forKey: @"RAW"];
    [result setObject: [NSString stringWithFormat:@"%@%@", proto, uriRaw]
            forKey: @"URI"];
    return [NSDictionary dictionaryWithDictionary:result];
}

+ (NSDictionary *) parseSmartPoster:(NSData *) payload {
    NSMutableDictionary *result = [[NSMutableDictionary alloc] init];
    int pos = 0;
    uint8_t recordHeader;
    do {
        recordHeader = ((uint8_t *) payload.bytes)[pos];
        uint8_t recordLength = ((uint8_t *) payload.bytes)[pos + 2];
        uint8_t recordType = ((uint8_t *) payload.bytes) [pos + 3];
        if (recordType == 0x55) {
            // URI
            NSDictionary *uriDictionary = [self parseUriPrimitive:[payload subdataWithRange:NSMakeRange(pos + 4, recordLength)]];
            if (uriDictionary != nil) {
                [result addEntriesFromDictionary:uriDictionary];
            }
        }
    pos = pos + recordLength + 4;
    } while ((pos < payload.length) || ((recordHeader & (1 << 6)) != 0x40));
    return [NSDictionary dictionaryWithDictionary:result];
}