mvvmcross touch command binding in android

Question

I\'m looking for a way to do a \"Touch\" command binding between axml and ViewModel, or some else like FocusChanged etc.

A simple \"Click\" command works fine like s

Answer 1

The framework can automatically bind any events which require EventHandler types. However, for any events which require a templated EventHandler (with custom EventArgs) then you are correct - you'll need to include a custom Binding.

The good news is that custom bindings are easy to write and to include.

For example, to bind:

public event EventHandler<View.LongClickEventArgs> LongClick;

you can include something like:

public class LongPressEventBinding
    : MvxBaseAndroidTargetBinding
{
    private readonly View _view;
    private IMvxCommand _command;

    public LongPressEventBinding(View view)
    {
        _view = view;
        _view.LongClick += ViewOnLongClick;
    }

    private void ViewOnLongClick(object sender, View.LongClickEventArgs eventArgs)
    {
        if (_command != null)
        {
            _command.Execute();
        }
    }

    public override void SetValue(object value)
    {
        _command = (IMvxCommand)value;
    }

    protected override void Dispose(bool isDisposing)
    {
        if (isDisposing)
        {
            _view.Click -= ViewOnLongClick;
        }
        base.Dispose(isDisposing);
    }

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

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

Which can be configured in setup using something like:

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

        registry.RegisterFactory(new MvxCustomBindingFactory<View>("LongPress", view => new LongPressEventBinding(view)));
    }

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Note that you can't write a single class that binds to all the different event types - as the compiler requires you to include the correct Type for the EventArgs. However, you could fairly easily change public class LongClickEventBinding to something like public class CustomEventBinding<TViewType, TEventArgsType> if you wanted to.

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With regards to what argument you should pass into the IMvxCommand Execute method, I guess this depends a bit on the method in question, and it also depends on whether you need the ViewModel to support multiple platforms, or whether it is just for Android.