使用DevicePicker枚举Bluetooth LE设备异常问题求助

Hey there, let's fix those frustrating DevicePicker problems you're facing with your BLE enumeration app. I've run into similar quirks before, so here's how to tackle both issues:

1. Empty DevicePicker Until Another App Scans #

The root cause here is that DevicePicker relies on the system's cached device list and doesn't automatically trigger a fresh BLE scan on its own. When you use another app like Bluetooth LE Explorer, it initiates a scan that populates the system cache—hence why your picker works afterward.

Fix: #

First, make sure your app has the required Bluetooth permissions. Add this to your Package.appxmanifest:

<Capabilities>
  <DeviceCapability Name="bluetooth" />
</Capabilities>

Then, replace your current device selectors with a more comprehensive one that targets all BLE devices (not just paired/unpaired states):

picker = new DevicePicker();
picker.DeviceSelected += ConnectToDevice;

// Clear existing selectors and use a universal BLE selector
picker.Filter.SupportedDeviceSelectors.Clear();
picker.Filter.SupportedDeviceSelectors.Add(BluetoothLEDevice.GetDeviceSelector());

Finally, trigger a quick temporary scan before showing the picker to populate the system cache:

// Start a short-lived DeviceWatcher to refresh the system's BLE device cache
var tempWatcher = DeviceInformation.CreateWatcher(BluetoothLEDevice.GetDeviceSelector());
tempWatcher.Start();

// Give it 500ms to scan (adjust based on your needs)
await Task.Delay(500);
tempWatcher.Stop();

// Now show the picker—it should have devices!
picker.Show(new Rect(0, 0, 200, 500), Windows.UI.Popups.Placement.Below);

2. Disconnected BLE Devices Still Appear in the List #

DevicePicker will show cached devices until the system updates its list. The temporary scan above helps, but you should also validate the device's availability when the user selects it:

Fix: #

Update your ConnectToDevice handler to check if the device is still reachable before attempting to connect:

private async void ConnectToDevice(DevicePicker sender, DevicePickerSelectedDeviceEventArgs args)
{
    // Try to retrieve the BLE device object
    var bleDevice = await BluetoothLEDevice.FromIdAsync(args.SelectedDevice.Id);
    
    if (bleDevice == null)
    {
        // Device is no longer available—alert the user
        var dialog = new Windows.UI.Popups.MessageDialog("This device is no longer reachable. Please select another.");
        await dialog.ShowAsync();
        return;
    }

    // Proceed with your existing connection logic here
}

Bonus Tip #

If you want more control over which devices appear, you can use BluetoothLEDevice.GetDeviceSelectorForBluetoothLEDevice() to filter by appearance categories, service UUIDs, or names. For example:

// Filter for devices with a specific service UUID
var selector = BluetoothLEDevice.GetDeviceSelectorForBluetoothLEDevice(
    null, 
    new Guid[] { Guid.Parse("0000FFE0-0000-1000-8000-00805F9B34FB") }, 
    BluetoothLEDeviceAppearanceCategories.Uncategorized
);
picker.Filter.SupportedDeviceSelectors.Add(selector);

内容的提问来源于stack exchange，提问作者Sha-1