How to bind to View's layout_weight in MvvmCross?

Question

What is the easiest way to bind to View's (or any other Android control) weight? Because this property doesn't have a setter, I tried custom binding, but id doesn't seem to work:

public class ViewWeightCustomBinding : MvxAndroidTargetBinding
{
    public ViewWeightCustomBinding(object target) : base(target)
    {
    }

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

    protected override void SetValueImpl(object target, object value)
    {
        var realTarget = target as View;
        if(target == null)
            return;

        ViewGroup.LayoutParams layoutParameters = realTarget.LayoutParameters;
        realTarget.LayoutParameters = new LinearLayout.LayoutParams(layoutParameters.Width, layoutParameters.Height,
                                                                  (int) value);
    }
}

registration in setup:

protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry)
{
    registry.RegisterFactory(new MvxSimplePropertyInfoTargetBindingFactory(typeof(ViewWeightCustomBinding), typeof(View), "ViewWeight"));
    base.FillTargetFactories(registry);
}

And .axml

 <View
        android:layout_width="0dp"
        android:layout_height="3dp"
        android:background="@color/green_holo"
        local:MvxBind="ViewWeight Id" />

I can see Waring in debug window:

[0:] MvxBind:Warning: 5.20 Failed to create target binding for binding ViewWeight for Id [0:] MvxBind:Warning: 5.20 Failed to create target binding for binding ViewWeight for Id 01-31 10:54:57.247 I/mono-stdout( 3795): MvxBind:Warning: 5.20 Failed to create target binding for binding ViewWeight for Id

As far as I know `layout_weight` can be set programatically using code like: http://stackoverflow.com/questions/3224193/set-the-layout-weight-of-a-textview-programmatically - so you could build a custom binding to support this. However, I don't know if the weight value can be easily changed dynamically after the layout has already been displayed. — Stuart, Jan 31 '14 at 11:41
It's possible to change the weight after layout being shown, I tested it in java android and it was ok. I used exactly the same code in my custom binding, but it doesn't work, it looks like there is a problem with binding itself. — user963935, Jan 31 '14 at 14:26

score 1 · Accepted Answer · answered Jan 31 '14 at 18:35

MvxSimplePropertyInfoTargetBindingFactory can only be used for real C# properties.

For invented "pseudo" properties, you need to use a custom binding registration like that shown in the n=28 tutorial -

    protected override void FillTargetFactories(Cirrious.MvvmCross.Binding.Bindings.Target.Construction.IMvxTargetBindingFactoryRegistry registry)
    {
        registry.RegisterCustomBindingFactory<BinaryEdit>(
                        "N28", 
                        binary => new BinaryEditFooTargetBinding(binary) );
        base.FillTargetFactories(registry);
    }

https://github.com/MvvmCross/NPlus1DaysOfMvvmCross/blob/master/N-28-CustomBinding/CustomBinding.Droid/Setup.cs

How to bind to View's layout_weight in MvvmCross?

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