MvvmCross convert bool to drawable in Android

Question

In my Xamarin Android app I'm trying to use a converter on a boolean to highlight the selected item in a list.

Does anyone know if it is even possible to use a converter on a boolean to select one or another drawable as the background of a LinearLayout ?

I feel like I'm missing something. I've tried returning various types from my converter, but nothing seems to work.

 <LinearLayout
    android:orientation="vertical"
    android:layout_width="wrap_content"
    local:MvxBind="Background IsSelected, Converter=BoolToDrawable"
    android:layout_height="wrap_content">

Answer 1

I have done something similar, I have an int (RowItem.SummaryEnumPlayersInt) which I convert to a drawable:

<TextView
    style="@style/TeamDifficulty"
    android:layout_width="15dp"
    android:layout_height="15dp"
    android:gravity="center"
    android:background="@drawable/background_circle"
    local:MvxBind="Text RowItem.SummaryEnumPlayersInt; Summary RowItem.SummaryEnumPlayers" />

Notice the custom "Summary" binding, this is where the magic happens, in setup:

protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry)
{
    base.FillTargetFactories(registry);

    registry.RegisterFactory(new MvxCustomBindingFactory<TextView>("Summary", textView => new SummaryTextViewBinding(textView)));
}

And here is that custom binding class:

public class SummaryTextViewBinding : MvxAndroidTargetBinding
{
    readonly TextView _textView;
    SummaryEnumeration _currentValue;

    public SummaryTextViewBinding(TextView textView) : base(textView)
    {
        _textView = textView;
    }

    #region implemented abstract members of MvxConvertingTargetBinding
    protected override void SetValueImpl(object target, object value)
    {            
        if (!string.IsNullOrEmpty(_textView.Text))
        {
            _currentValue = (SummaryEnumeration)Convert.ToInt32(_textView.Text);

            SetTextViewBackground();
        }
    }
    #endregion

    void SetTextViewBackground()
    {
        switch (_currentValue)
        {
            case SummaryEnumeration.Easy:
                _textView.SetBackgroundResource(Resource.Drawable.background_circle_green);
                _textView.Text = string.Empty;

                break;
            case SummaryEnumeration.Medium:
                _textView.SetBackgroundResource(Resource.Drawable.background_circle_yellow);
                _textView.Text = string.Empty;

                break;
            case SummaryEnumeration.Difficult:
                _textView.SetBackgroundResource(Resource.Drawable.background_circle_red);
                _textView.Text = string.Empty;

                break;
            case SummaryEnumeration.None:
                _textView.SetBackgroundResource(Resource.Drawable.background_circle_none);
                _textView.Text = LocalizationConstants.Nothing;

                break;
        }
    }

    public override Type TargetType
    {
        get { return typeof(bool); }
    }

    public override MvxBindingMode DefaultMode
    {
        get { return MvxBindingMode.OneWay; }
    }
}

Enjoy!