如何将 StreamSubscription 与 Flutter Riverpod 结合使用

Question

我正在使用 FlutterReactiveBle 来“监听”和传输我的命令并发送自定义特征。因此，我决定在 Riverpod 中创建一个 StateProvider，用我的特征（蓝牙）侦听器中收到的数据填充字符串列表。

final bluetoothServiceProvider = Provider<BluetoothService>((ref) {
  return BluetoothService();
});

final streamDataProvider = StateProvider<List<String>>((ref) {
  return [];
});

final streamSubscriptionProvider = StateProvider.family<void, bool>((ref, onOff) {
  final characteristicTX = QualifiedCharacteristic(
    serviceId: SERVICE_UUID,
    characteristicId: CHARACTERISTIC_TX_UUID,
    deviceId: "60:A4:23:C9:10:10",
  );
  final socket = ref
      .read(bluetoothServiceProvider)
      .flutterReactiveBle
      .subscribeToCharacteristic(characteristicTX)
      .listen((event) {
    ref.read(streamDataProvider.notifier).state = [
      ...ref.read(streamDataProvider.notifier).state,
      "${DateTime.now()} - ${utf8.decode(event)}",
    ];
  });

  if (onOff) {
    print("RESUME");
    socket.resume();
    print(socket.isPaused);
  } else {
    print("CANCEL");
    socket.cancel();
    print(socket.isPaused);
  }
});

这是我的 HomeView，我可以在其中发送命令并在 ListView 中显示来自

streamDataProvider

的数据。

return Scaffold(
  appBar: AppBar(title: const Text("APP")),
  body: Column(
    children: [
      const SizedBox(height: 20),
      Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          ElevatedButton(
            onPressed: () async {
              ref.read(streamSubscriptionProvider(true));
            },
            child: const Text("Turn on stream"),
          ),
          const SizedBox(width: 20),
          ElevatedButton(
            onPressed: () async {
              ref.read(streamSubscriptionProvider(false));
            },
            child: const Text("Turn off stream"),
          ),
        ],
      ),
      const SizedBox(height: 20),
      Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          ElevatedButton(
            onPressed: () async {
              await ref.read(bluetoothServiceProvider).getVersion(mine);
            },
            child: const Text("Send command 'Get version'"),
          ),
        ],
      ),
      const SizedBox(height: 20),
      Expanded(
        child: Card(
          margin: const EdgeInsets.all(10),
          child: ListView.builder(
            padding: const EdgeInsets.all(10),
            itemCount: ref.watch(streamDataProvider).length,
            itemBuilder: (BuildContext context, int index) {
              return Text(
                ref.watch(streamDataProvider)[index],
                style: const TextStyle(fontSize: 8),
              );
            },
          ),
        ),
      ),
    ],
  ),
);

问题是我不明白如何用按钮停止或恢复

streamSubscription

。套接字永远不会被取消，并且我仍然在 ListView 中接收数据。

这是我用于 BLE 的库：flutter_reactive_ble。

Answer 1

List<T>

没有可用作原始家庭密钥的

==

方法。您需要使用生成的提供程序，它可以解决这个问题，或者使用来自

fast_immutable_collections

的 IList<T> 之类的东西。