Xamarin Forms蓝牙LE无法扫描到附近可发现设备问题求助

Hey Brian, let's dig into why your Bluetooth scan isn't picking up the Samsung J7 even though the scan flag returns true. I've worked with Monkey.BluetoothLE quite a bit, so here are some targeted checks and fixes to try out:

Monkey.BluetoothLE depends on proper runtime permissions, especially on Android 6.0+. Even if you've added permissions to your AndroidManifest.xml, you need to explicitly request them at runtime.

• Bluetooth scanning on Android requires location permissions (ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION) — yes, even if you don't plan to use location data. Make sure your app has these permissions granted before starting a scan.
• Add a quick permission check before initiating the scan. Here's a snippet to reference:

if (!CrossBluetoothLE.Current.Adapter.IsScanning)
{
    if (await CheckRequiredPermissionsAsync()) // Replace with your permission check logic
    {
        CrossBluetoothLE.Current.Adapter.ScanTimeout = 15000;
        CrossBluetoothLE.Current.Adapter.DeviceDiscovered += OnDeviceDiscovered;
        await CrossBluetoothLE.Current.Adapter.StartScanningForDevicesAsync();
    }
}

• Sometimes the Bluetooth adapter needs a moment to initialize after app launch. Add a check to ensure the adapter is ready before scanning:

while (!CrossBluetoothLE.Current.IsAvailable || !CrossBluetoothLE.Current.Adapter.IsEnabled)
{
    await Task.Delay(500);
}

• Avoid unintentional device filtering. If you're using StartScanningForDevicesAsync with a service UUID filter, remove it temporarily to scan all visible devices — this will confirm if the filter is blocking the J7.

Older Samsung models like the J7 have occasional Bluetooth stack quirks:

• On the target J7, go to Settings > Connections > Bluetooth > Advanced and make sure the "Scan for nearby devices" toggle is enabled (some devices hide this option in advanced settings).
• Reboot both your test device (J7 Pro) and the target J7 — Bluetooth stacks can get stuck, and a simple reboot often resolves detection issues.
• Test scanning with another Bluetooth device (like a wireless headset) to rule out app-specific problems. If your app detects other devices, the issue might be with the J7's advertising configuration.

• Add detailed logging to the DeviceDiscovered event to see if any devices are being detected at all:

private void OnDeviceDiscovered(object sender, DeviceEventArgs e)
{
    Debug.WriteLine($"Found device: {e.Device.Name} | ID: {e.Device.Id}");
    vm.Add(new BluetoothViewModel(e.Device));
}

• Also verify that the ScanTimeoutElapsed event fires, which confirms the scan is running for the full intended duration.

• Ensure you're using the latest stable version of Monkey.BluetoothLE — older versions might have bugs with Android 10+ or Samsung-specific Bluetooth implementations.
• For Android, confirm your AndroidManifest.xml includes all necessary permissions (adjust for Android 12+ if needed):

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true" />
<!-- For Android 12+ -->
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" />

Start with these steps — more often than not, the issue boils down to a missing permission or a hidden device setting that's easy to overlook.

内容的提问来源于stack exchange，提问作者Brian Kingdom