Bluetooth Plugin.Ble not showing any device.

Question

I am using visual studio 2022 Maui, installed latest update and bluetooth Plugin.Ble ver 3.
Also added all permission

#if ANDROID
		public override (string androidPermission, bool isRuntime)[] RequiredPermissions => new List<(string Permission, bool isRuntime)>
		 {
			    (Android.Manifest.Permission.BluetoothScan, true),
                (Android.Manifest.Permission.BluetoothConnect, true)
		 }.ToArray();
#endif

Also added runtime permission . Also Manually added.

async Task RequestBluetooth()
{
    if (DeviceInfo.Platform != DevicePlatform.Android) { return; }
    var Status = PermissionStatus.Unknown;
    if (DeviceInfo.Version.Major >= 12)
    {
        Status = await Permissions.CheckStatusAsync<BluetoothPermissions>();
        if (Status == PermissionStatus.Granted)
        {
            return;
        }
        if (Permissions.ShouldShowRationale<BluetoothPermissions>())
        {
            await Shell.Current.DisplayAlert("Permission needs", "Bluetooth", "Ok");
        }
        Status = await Permissions.RequestAsync<BluetoothPermissions>();
    }
    else
    {
        if (Status != PermissionStatus.Granted)
        {
            await Shell.Current.DisplayAlert("Permission Required", "Bluetooth", "Ok");
        }
    }
}

My Code is . Scanning shows no device . Please help me what is the problem.

private async Task ScanAsync() {     var ble = CrossBluetoothLE.Current;     var adapter = CrossBluetoothLE.Current.Adapter;     var state = ble.State;     adapter.ScanTimeout = 20000;     await RequestBluetooth();     await adapter.StartScanningForDevicesAsync();     List<string> deviceList = new List<string>();     ToastDuration duration = ToastDuration.Long;     double fontSize = 18;     if (deviceList.Count == 0)     {         string text = "Unable to find Bluetooth LE devices";         var toast = Toast.Make(text, duration, fontSize);         CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();         await toast.Show(cancellationTokenSource.Token);         return;     }     else     {         string text = "Found Devices";         var toast = Toast.Make(text, duration, fontSize);         CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();         await toast.Show(cancellationTokenSource.Token);         foreach (var device in deviceList)         {             deviceList.Add(device);         }     } }

Answer 1

Hello,

Thanks for your feedback.

In accordance with the forum's privacy policy, I removed the link to the sample project.

After testing, you can follow the steps below to implement the Bluetooth scanning function.

Step 1. Add these relevant permissions in your Android manifest.

<uses-permission
   android:name="android.permission.ACCESS_COARSE_LOCATION"
   android:maxSdkVersion="30" />
<uses-permission
    android:name="android.permission.ACCESS_FINE_LOCATION"
    android:maxSdkVersion="30" />
<uses-permission
    android:name="android.permission.BLUETOOTH"
    android:maxSdkVersion="30" />
<uses-permission
    android:name="android.permission.BLUETOOTH_ADMIN"
    android:maxSdkVersion="30" />
<!-- Android 12 must add android:usesPermissionFlags="neverForLocation" when not applying for location permission, otherwise the devices will not be found -->
<uses-permission
    android:name="android.permission.BLUETOOTH_SCAN"
    android:usesPermissionFlags="neverForLocation" />
<uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />

Step 2. Dynamically request for permissions in the MainActivity.

public class MainActivity : MauiAppCompatActivity
{
    private const int REQUEST_PERMISSION_CODE = 1001;

    protected override void OnCreate(Bundle? savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        initPermission();
    }
    private void initPermission()
    {
        List<String> mPermissionList = new List<string>();
        // When the Android version is 12 or greater, apply for new Bluetooth permissions
        if (Build.VERSION.SdkInt >= BuildVersionCodes.S)
        {
            mPermissionList.Add(Manifest.Permission.BluetoothScan);
            mPermissionList.Add(Manifest.Permission.BluetoothAdvertise);
            mPermissionList.Add(Manifest.Permission.BluetoothConnect);
            //Request for location permissions based on your actual needs
            //mPermissionList.add(Manifest.permission.ACCESS_COARSE_LOCATION);
            //mPermissionList.add(Manifest.permission.ACCESS_FINE_LOCATION);
        }
        else
        {
            mPermissionList.Add(Manifest.Permission.AccessCoarseLocation);
            mPermissionList.Add(Manifest.Permission.AccessFineLocation);
        }

        ActivityCompat.RequestPermissions(this, mPermissionList.ToArray(), REQUEST_PERMISSION_CODE);
    }
}

Step 3. Invoke scan function.

var adapter = CrossBluetoothLE.Current.Adapter;
var state = ble.State;
adapter.ScanTimeout = 20000;
//await RequestBluetooth();
await adapter.StartScanningForDevicesAsync(); // Add this line before the applicaiton can get the list of Bluetooth devices.

Best Regards,

Alec Liu.

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