iOS: External media source selection

Airplay is a great feature in iOS. So I needed a UI for selection. Also a Slider for the volume. There is an open source project which has a default GUI implementation. But there are problems:

• Some not reproducible NullException (thats the reason I cannot make an issue for that
• Slider and Airplay Button are fixed in UI

So I had a look into it. We have to use MPVolumeView for the volume and AVRoutePickerView (iOS11+) for selection of the external sources.
Here es an example how it can be implemented in the GUI (Cuterdio). We have a separate slider and a separate button for Airplay:

The example let you pass a Slider which can feedback the volume change.

public class AudioManagerIos : IAudioManager
{
  public Slider Slider { get; set; }
  private UISlider _slider;
  
  public AudioManagerIos()
  {
    MPVolumeView mpVolumeView = new MPVolumeView();  
    _slider = mpVolumeView.Subviews.OfType<UISlider>().FirstOrDefault();
    if (_slider != null)
    {
      _slider.ValueChanged += _slider_ValueChanged;
    }
  }

  private void _slider_ValueChanged(object sender, EventArgs e)
  {
    Volume = _slider.Value;
  }

  public void ShowExternalDevices()
  {
    var routePickerView = new AVRoutePickerView();
    var button = routePickerView.Subviews.OfType<UIButton>().FirstOrDefault();
    button?.SendActionForControlEvents(UIControlEvent.TouchUpInside);
    routePickerView.Dispose();
  }

  public float Volume
  {
    get
    {
      return _slider.Value;
    }
    set
    {
      _slider.Value = value;
      if (Slider != null)
      {
        Slider.Value = _slider.Value;
      }
    }
  }
}