In MvvmCross how do I do custom bind properties

Question

I am using MvxBindableListView to bind a List<> of data objects to a ListView. The layout I am using for the rows has several TextViews. I am successfully binding the Text property for each of these to a property in my data object, but I have found that I cannot bind to TextColor as that property does not exist in Mono For Android TextViews; instead you have use the SetTextColor() method. So how can I bind a data object property to a method?! Below is the code I tried to use:

    <TextView
        android:id="@+id/MyValueTextView"
        android:layout_width="50dp"
        android:layout_height="20dp"
        android:layout_gravity="right"
        android:gravity="center_vertical|right"
        android:textSize="12sp"
        local:MvxBind="
        {
          'Text':{'Path':'MyValue','Converter':'MyValueConverter'},
          'TextColor':{'Path':'MyOtherValue','Converter':'MyOtherConverter'}
        }" />

Answer 1

There's an example of adding a custom 2-way binding for "IsFavorite" in the Conference sample - see:

• the binding - https://github.com/slodge/MvvmCross/blob/master/Sample%20-%20CirriousConference/Cirrious.Conference.UI.Droid/Bindings/FavoritesButtonBinding.cs
• the binding setup in FillTargetFactories in https://github.com/slodge/MvvmCross/blob/master/Sample%20-%20CirriousConference/Cirrious.Conference.UI.Droid/Setup.cs

This example is explained a bit further in: MVVMCross Bindings in Android

For a one-way "source-to-target" custom binding, the code should be a bit simpler - you only need to handle the SetValue - and don't need to invoke FireValueChanged in any event handling code.

---

For textColor, I'd imagine the binding would look a bit like:

public class MyCustomBinding
    : MvxBaseAndroidTargetBinding
{
    private readonly TextView _textView;

    public MyCustomBinding(TextView textView)
    {
        _textView = textView;
    }

    public override void SetValue(object value)
    {
        var colorValue = (Color)value;
        _textView.SetTextColor(colorValue);
    }

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

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

and would be setup with:

    protected override void FillTargetFactories(MvvmCross.Binding.Interfaces.Bindings.Target.Construction.IMvxTargetBindingFactoryRegistry registry)
    {
        base.FillTargetFactories(registry);

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

Note: I've not compiled this example code - when you do get it working, please come back and correct this pseudo-code :)