Flutter NFC信息读取插件nfc_info的使用

Flutter NFC信息读取插件nfc_info的使用

这个包是为了让Flutter应用程序能够在应用从后台切换到前台时获取NFC标签传递的数据。

请注意，这是该包的第一个版本，在某些方面我并不确定，特别是在iOS平台上。

完整示例代码

import 'package:flutter/material.dart';
import 'dart:async';

import 'package:flutter/services.dart';
import 'package:nfc_info/nfc_info.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  [@override](/user/override)
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  String _platformVersion = '未知';
  String? _initialNfc = "";
  String _latestNfc = "";
  StreamSubscription? _sub;

  [@override](/user/override)
  void initState() {
    super.initState();
    WidgetsBinding.instance!.addObserver(this);
    initPlatformState();
    getInitialNfcInfo();
    listenToNfcStream();
  }

  [@override](/user/override)
  void dispose() {
    WidgetsBinding.instance!.removeObserver(this);
    _sub?.cancel();
    super.dispose();
  }

  [@override](/user/override)
  void didChangeAppLifecycleState(AppLifecycleState state) {
    switch (state) {
      case AppLifecycleState.resumed:
        print("app resumed");
        // getNfcInfo();
        break;
      default:
        break;
    }
  }

  // 平台消息是异步的，所以我们通过异步方法进行初始化。
  Future<void> initPlatformState() async {
    String platformVersion;
    // 平台消息可能会失败，所以我们使用try/catch来捕获PlatformException。
    try {
      platformVersion = await NfcInfo.platformVersion;
    } on PlatformException {
      platformVersion = '获取平台版本失败。';
    }

    // 如果小部件在异步平台消息执行期间从树中移除，我们希望丢弃回复而不是调用setState来更新我们的非存在的外观。
    if (!mounted) return;

    setState(() {
      _platformVersion = platformVersion;
    });
  }

  Future<void> getInitialNfcInfo() async {
    String? nfc = "";
    try {
      nfc = await (NfcInfo.getInitialText() as FutureOr<String>);
    } on PlatformException {
      print("getInitialNfcInfo: 错误 getInitialText()");
    }
    print('getInitialNfcInfo: $nfc');
    if (!mounted) return;
    setState(() {
      _initialNfc = nfc;
    });
    // ��icoffee://www.icoffee.app/shops/123
    if (nfc != null && nfc.isNotEmpty) {
      /// TODO 如果我们得到了nfc，需要清除
      /// 这样当应用程序从前台切换到后台时，应用程序将不会再次处理相同的旧NFC数据。
      // await NfcInfo.reset();
    }
  }

  void listenToNfcStream() {
    _sub = NfcInfo.getTextsStream().listen((String nfc) {
      if (!mounted) return;
      print("nfc from stream: $nfc");
      setState(() {
        _latestNfc = nfc;
      });
    }, onError: (Object err) {
      if (!mounted) return;
      print(err.toString());
    });
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('NFC信息'),
        ),
        body: Column(
          children: [
            Text('运行于: $_platformVersion\n'),
            Text('收到的nfc: $_initialNfc'),
            Text('nfc流: $_latestNfc'),
          ],
        ),
        floatingActionButton: FloatingActionButton(
          child: Icon(Icons.nfc),
          onPressed: getInitialNfcInfo,
        ),
      ),
    );
  }
}

说明

1. 导入必要的库：

   import 'package:flutter/material.dart';
   import 'dart:async';
   
   import 'package:flutter/services.dart';
   import 'package:nfc_info/nfc_info.dart';
   

2. 初始化状态：

   void initState() {
     super.initState();
     WidgetsBinding.instance!.addObserver(this);
     initPlatformState();
     getInitialNfcInfo();
     listenToNfcStream();
   }
   

3. 获取平台版本：

   Future<void> initPlatformState() async {
     String platformVersion;
     try {
       platformVersion = await NfcInfo.platformVersion;
     } on PlatformException {
       platformVersion = '获取平台版本失败。';
     }
     if (!mounted) return;
     setState(() {
       _platformVersion = platformVersion;
     });
   }
   

4. 获取初始NFC信息：

   Future<void> getInitialNfcInfo() async {
     String? nfc = "";
     try {
       nfc = await (NfcInfo.getInitialText() as FutureOr<String>);
     } on PlatformException {
       print("getInitialNfcInfo: 错误 getInitialText()");
     }
     print('getInitialNfcInfo: $nfc');
     if (!mounted) return;
     setState(() {
       _initialNfc = nfc;
     });
   }
   

5. 监听NFC流：

   void listenToNfcStream() {
     _sub = NfcInfo.getTextsStream().listen((String nfc) {
       if (!mounted) return;
       print("nfc from stream: $nfc");
       setState(() {
         _latestNfc = nfc;
       });
     }, onError: (Object err) {
       if (!mounted) return;
       print(err.toString());
     });
   }
   

6. 构建UI：

   [@override](/user/override)
   Widget build(BuildContext context) {
     return MaterialApp(
       home: Scaffold(
         appBar: AppBar(
           title: const Text('NFC信息'),
         ),
         body: Column(
           children: [
             Text('运行于: $_platformVersion\n'),
             Text('收到的nfc: $_initialNfc'),
             Text('nfc流: $_latestNfc'),
           ],
         ),
         floatingActionButton: FloatingActionButton(
           child: Icon(Icons.nfc),
           onPressed: getInitialNfcInfo,
         ),
       ),
     );
   }