c# - 为什么 BluetoothLEDevice.GattServices 为空

Question

我正在尝试与外围设备通信而不将其与 Windows 配对，并且我正在使用 BluetoothLEAdvertisementWatcher 扫描范围内的设备。这是我的 WatcherOnReceived 方法:

 async private void WatcherOnReceived(BluetoothLEAdvertisementWatcher sender, BluetoothLEAdvertisementReceivedEventArgs args)
    {
        BluetoothLEDevice device = null;
        BluetoothDevice basicDevice = null;
        GattDeviceService services = null;

        if (args.Advertisement.LocalName != "Nexus 6")
            return;

        _watcher.Stop();

        device = await BluetoothLEDevice.FromBluetoothAddressAsync(args.BluetoothAddress);
        device.GattServicesChanged += Device_GattServicesChanged;
        //basicDevice = await BluetoothDevice.FromBluetoothAddressAsync(args.BluetoothAddress);
        //services = await GattDeviceService.FromIdAsync(device.DeviceId);

        lock (m_syncObj)
        {
            Debug.WriteLine("");
            Debug.WriteLine("----------- DEVICE --------------");

            Debug.WriteLine(args.ToString());

            Debug.WriteLine(args.Advertisement.DataSections.Count);

            foreach (var item in args.Advertisement.DataSections)
            {
                var data = new byte[item.Data.Length];
                using (var reader = DataReader.FromBuffer(item.Data))
                {
                    reader.ReadBytes(data);
                }

                Debug.WriteLine("Manufacturer data: " + BitConverter.ToString(data));

                //Debug.WriteLine("Data : " + item.Data.ToString());
                //Debug.WriteLine("Data capacity: " + item.Data.Capacity);
                Debug.WriteLine("Data Type: " + item.DataType);
            }

            foreach (var md in args.Advertisement.ManufacturerData)
            {
                var data = new byte[md.Data.Length];
                using (var reader = DataReader.FromBuffer(md.Data))
                {
                    reader.ReadBytes(data);
                }
                Debug.WriteLine("Manufacturer data: " + BitConverter.ToString(data));
            }

            foreach (Guid id in args.Advertisement.ServiceUuids)
            {
                Debug.WriteLine("UUIDs: " + id.ToString() + " Count: " + args.Advertisement.ServiceUuids.Count);
                //services = device.GetGattService(id);
            }

            Debug.WriteLine("Receive event...");
            Debug.WriteLine("BluetoothAddress: " + args.BluetoothAddress.ToString("X"));
            Debug.WriteLine("Advertisement.LocalName: " + args.Advertisement.LocalName);
            Debug.WriteLine("AdvertisementType: " + args.AdvertisementType);
            Debug.WriteLine("RawSignalStrengthInDBm: " + args.RawSignalStrengthInDBm);

            if (device != null)
            {
                Debug.WriteLine("Bluetooth Device: " + device.Name);
                Debug.WriteLine("Bluetooth Device conn status: " + device.ConnectionStatus);
                Debug.WriteLine("Bluetooth DeviceId: " + device.DeviceId);
                Debug.WriteLine("Bluetooth GettServices Count: " + device.GattServices.Count);
            }
        }   
    }

收到设备后，我从 args.BlutoothAddress 成功创建了 BluetoothLEDevice，但 device.GattServices 始终为空，因此我无法使用它们与设备通信。是设备问题还是 Windows API 问题，我还能尝试什么？

Answer 1

更新 04/17 - 创作者更新Microsoft 刚刚更新了他们的蓝牙 API。我们现在有未配对的 BLE 设备通信!

目前他们的文档很少，但这里是简化得多的新结构:

BleWatcher = new BluetoothLEAdvertisementWatcher 
{ 
    ScanningMode = BluetoothLEScanningMode.Active
};
BleWatcher.Start();

BleWatcher.Received += async (w, btAdv) => {
    var device = await BluetoothLEDevice.FromBluetoothAddressAsync(btAdv.BluetoothAddress);
Debug.WriteLine($"BLEWATCHER Found: {device.name}");

    // SERVICES!!
    var gatt = await device.GetGattServicesAsync();
    Debug.WriteLine($"{device.Name} Services: {gatt.Services.Count}, {gatt.Status}, {gatt.ProtocolError}");

    // CHARACTERISTICS!!
    var characs = await gatt.Services.Single(s => s.Uuid == SAMPLESERVICEUUID).GetCharacteristicsAsync();
    var charac = characs.Single(c => c.Uuid == SAMPLECHARACUUID);
    await charac.WriteValueAsync(SOMEDATA);
};

现在好多了。正如我所说，目前几乎没有文档，我有一个奇怪的问题，我的 ValueChanged 回调在 30 秒左右后停止被调用，尽管这似乎是一个单独的范围问题。

更新 2 - 一些奇怪的地方

在尝试了新的创作者更新之后，在构建 BLE 应用程序时需要考虑更多事项。

• 您不再需要在 UI 线程上运行蓝牙。如果没有配对，BLE 似乎没有任何权限窗口，因此不再需要在 UI 线程上运行。您可能会发现您的应用程序在一段时间后停止从设备接收更新。这是一个范围界定问题，其中不应该处理对象。在上面的代码中，如果您在 charac 上收听 ValueChanged，您可能会遇到此问题。这是因为 GattCharacteristic 在它应该被处理之前就被处理掉了，将特性设置为全局特性而不是依赖于它被复制进来。断开连接似乎有点坏了。退出应用程序不会终止连接。因此，请确保您使用 App.xml.cs OnSuspended 回调来终止您的连接。否则你会进入一种奇怪的状态，Windows 似乎在维护(并继续阅读!!)BLE 连接。好吧，它有它的怪癖，但它确实有效!

• 这仍然是 Windows 通用应用程序的问题，最初的问题是设备必须配对(而非绑定(bind))才能发现 GattServices。但是，还需要使用 Windows 设备而不是 BLE API 来发现它们。 Microsoft 知道并正在开发不需要配对的新 BLE API，但坦率地说，在准备就绪之前，他们的 BLE 支持非常无用。

• 尝试在控制面板中手动配对设备，然后再次列出服务。由于某些原因，在 Windows Universal Apps 中您只能列出配对设备的 Gatt 服务，尽管 BLE 的优势之一是您在使用其服务之前无需与设备配对。

您可以通过编程方式配对设备，但是根据运行应用程序的平台，这需要 UI 提示。因此在后台查询 BLE 服务是不可行的。这需要修复，因为它确实阻碍了 UWP 中的 BLE 支持。

这很奇怪但很管用!

旧答案

下面是一些具有工作 BLE 设备连接的示例代码:

    private void StartWatcher()
    {
        ConnectedDevices = new List<string>();

        Watcher = new BluetoothLEAdvertisementWatcher { ScanningMode = BluetoothLEScanningMode.Active };
        Watcher.Received += DeviceFound;

        DeviceWatcher = DeviceInformation.CreateWatcher();
        DeviceWatcher.Added += DeviceAdded;
        DeviceWatcher.Updated += DeviceUpdated;

        StartScanning();
    }

    private void StartScanning()
    {
        Watcher.Start();
        DeviceWatcher.Start();
    }

    private async void DeviceFound(BluetoothLEAdvertisementWatcher watcher, BluetoothLEAdvertisementReceivedEventArgs btAdv)
    {
        if (!ConnectedDevices.Contains(btAdv.Advertisement.LocalName) && _devices.Contains(btAdv.Advertisement.LocalName))
        {
            await Dispatcher.RunAsync(CoreDispatcherPriority.Low, async () =>
            {
                var device = await BluetoothLEDevice.FromBluetoothAddressAsync(btAdv.BluetoothAddress);
                if (device.GattServices.Any())
                {
                    ConnectedDevices.Add(device.Name);
                    device.ConnectionStatusChanged += (sender, args) =>
                    {
                        ConnectedDevices.Remove(sender.Name);
                    };
                    SetupWaxStream(device);
                } else if (device.DeviceInformation.Pairing.CanPair && !device.DeviceInformation.Pairing.IsPaired)
                {
                    await device.DeviceInformation.Pairing.PairAsync(DevicePairingProtectionLevel.None);
                }
            });
        }
    }

    private async void DeviceAdded(DeviceWatcher watcher, DeviceInformation device)
    {
        if (_devices.Contains(device.Name))
        {
            try
            {
                var service = await GattDeviceService.FromIdAsync(device.Id);
                var characteristics = service.GetAllCharacteristics();
            }
            catch
            {
                Debug.WriteLine("Failed to open service.");
            }
        }
    }

    private async void DeviceUpdated(DeviceWatcher watcher, DeviceInformationUpdate update)
    {
        var device = await DeviceInformation.CreateFromIdAsync(update.Id);
        if (_devices.Contains(device.Name))
        {
            try
            {
                var service = await GattDeviceService.FromIdAsync(device.Id);
                var characteristics = service.GetAllCharacteristics();
            }
            catch
            {
                Debug.WriteLine("Failed to open service.");
            }
        }
    }