xamarin-bluetooth-le does not scan devices - xamarin

Question

I am using xamarin-bluetooth-le to make BluetoothLE client side on Xamarin.
I searched few of BluetoothLE package (sample code is work fine).
Thus, I have choosed xamarin-bluetooth-le.
In fact, sample code work fine.
However, I am simplify sample code without view, becuse I am not need View and binding is not need.
However xamarin-bluetooth-le does not scan device by the simplify code.
First question:
In sample of xamarin-bluetooth-le, an event named DeviceDiscovered is need assign two times?(one is DeviceListViewModel constructor, the other is scan method).
Second(main) question:
Why xamarin-bluetooth-le does not scan device by below codes?
Environment is
Visual Studio 2019 16.10.0
Xamarin 16.10.000.228
Plugin.BLE 2.1.2
Other newest
Below is code:
BluetoothClient.cs
using Plugin.BLE;
using Plugin.BLE.Abstractions.Contracts;
using Plugin.BLE.Abstractions.EventArgs;
using Plugin.BLE.Abstractions.Extensions;
using System;
using System.Collections.ObjectModel;
using System.Threading;
using System.Threading.Tasks;
namespace PlugInBLETest.NetowrkModels
{
public class BluetoothBLEClient
{
private IAdapter Adapter;
private IBluetoothLE Current;
public ObservableCollection<IDevice> DeviceList { get; }
private CancellationTokenSource CancelSource;
public BluetoothBLEClient()
{
Current = CrossBluetoothLE.Current;
Adapter = CrossBluetoothLE.Current.Adapter;
Adapter.DeviceDiscovered += OnDeviceDiscovered;
Adapter.ScanTimeoutElapsed += OnScanTimeoutElapsed;
Adapter.DeviceDisconnected += OnDeviceDisconnected;
Adapter.DeviceConnectionLost += OnDeviceConnectionLost;
DeviceList = new ObservableCollection<IDevice>();
}
public async Task SearchDevices()
{
if (Current.State == BluetoothState.Off)
{
return;
}
else
{
DeviceList.Clear();
foreach (var connectedDevice in Adapter.ConnectedDevices)
{
try
{
await connectedDevice.UpdateRssiAsync();
}
catch (Exception ex)
{
return;
}
}
CancelSource = new CancellationTokenSource();
Adapter.ScanMode = ScanMode.LowLatency;
Adapter.ScanTimeout = 30000;
//Adapter.DeviceDiscovered += (s, a) => DeviceList.Add(a.Device);
Adapter.DeviceDiscovered += (s, a) =>
{
DeviceList.Add(a.Device);
};
await Adapter.StartScanningForDevicesAsync(CancelSource.Token);
var temp = DeviceList.Count;
}
return;
}
private void OnDeviceConnectionLost(object sender, DeviceErrorEventArgs e)
{
}
private void OnDeviceDisconnected(object sender, DeviceEventArgs e)
{
}
private void OnScanTimeoutElapsed(object sender, EventArgs e)
{
}
private void OnDeviceDiscovered(object sender, DeviceEventArgs args)
{
}
}
}
AndroidManifext.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.companyname.pluginbletest">
<uses-sdk android:targetSdkVersion="30" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<application android:label="PlugInBLETest.Android" android:theme="#style/MainTheme"></application>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
</manifest>

Answer 1

Xamarin.Essentials has a permissions feature that will allow you to check for and request permission for access to the location data
After Marshmallow you have to prompt for the user for permission -> https://devblogs.microsoft.com/xamarin/requesting-runtime-permissions-in-android-marshmallow/