How can I detect Bluetooth state changes using a broadcast receiver in MvvmCross

Step 1: Register the MvvmCross BLE Plugin

First, ensure you have the MvvmCross BLE plugin installed in your project. This plugin provides a simple way to access Bluetooth functionality in MvvmCross applications. You can install it via NuGet:

bash
Install-Package Plugin.BLE

or using the .NET CLI:

bash
dotnet add package Plugin.BLE

Step 2: Implement the BroadcastReceiver

To detect Bluetooth state changes, you'll need to create a `BroadcastReceiver` that listens for the `android.bluetooth.adapter.action.STATE_CHANGED` intent. However, for Android API 26 and above, you cannot declare this receiver in the manifest file; instead, you must register it programmatically.

Here's how you can implement the receiver in a Xamarin.Android context:

csharp
using Android.App;
using Android.Bluetooth;
using Android.Content;
using MvvmCross.Platform;

public class BluetoothStateReceiver : BroadcastReceiver
{
    public override void OnReceive(Context context, Intent intent)
    {
        string action = intent.Action;

        if (action != BluetoothAdapter.ActionStateChange)
            return;

        int state = intent.GetIntExtra(BluetoothAdapter.ExtraState, BluetoothAdapter.Error);

        switch (state)
        {
            case BluetoothAdapter.StateOff:
                // Bluetooth is off
                break;
            case BluetoothAdapter.StateTurningOff:
                // Bluetooth is turning off
                break;
            case BluetoothAdapter.StateOn:
                // Bluetooth is on
                break;
            case BluetoothAdapter.StateTurningOn:
                // Bluetooth is turning on
                break;
        }
    }
}

Step 3: Register the BroadcastReceiver

You need to register the receiver in your activity or fragment's `OnResume` method and unregister it in the `OnPause` method to avoid leaks.

csharp
public class MyActivity : MvxActivity
{
    private BluetoothStateReceiver _receiver;

    protected override void OnResume()
    {
        base.OnResume();
        RegisterReceiver();
    }

    protected override void OnPause()
    {
        base.OnPause();
        UnregisterReceiver();
    }

    private void RegisterReceiver()
    {
        _receiver = new BluetoothStateReceiver();
        RegisterReceiver(_receiver, new IntentFilter(BluetoothAdapter.ActionStateChange));
    }

    private void UnregisterReceiver()
    {
        if (_receiver != null)
        {
            UnregisterReceiver(_receiver);
            _receiver = null;
        }
    }
}

Step 4: Integrate with MvvmCross

To integrate this functionality with MvvmCross, you can inject the `IBluetoothLE` service provided by the MvvmCross BLE plugin into your view model. However, for detecting Bluetooth state changes specifically, you'll rely on the broadcast receiver as shown above.

In your view model, you can react to Bluetooth state changes by handling the logic within the `OnReceive` method of the broadcast receiver or by notifying the view model from there.

csharp
public class MyViewModel : MvxViewModel
{
    private readonly IBluetoothLE _ble;

    public MyViewModel(IBluetoothLE ble)
    {
        _ble = ble;
    }

    // You can react to Bluetooth state changes here if needed
}

Permissions

Ensure you have the necessary Bluetooth permissions in your `AndroidManifest.xml`:

xml

Conclusion

By following these steps, you can effectively detect Bluetooth state changes using a broadcast receiver in an MvvmCross application. This approach allows your app to respond to Bluetooth state changes even when it's not in the foreground, although for API 26 and above, you must register the receiver programmatically.