How do I do two-way binding to a UITextView control using mvvmcross?

问题

I have a simple view I created using XCode (it's a XIB). It consists of two UITextView controls and a UIButton. I've exposed the UITextView controls as Outlets and given them names. Everything looks good in my View.designer.cs file.

I'm creating my binding using this syntax:

        this.AddBindings(
            new Dictionary<object, string>()
            {
                {lastname, "{'Text':{'Path':'LastName','Mode':'TwoWay'}}"},
                {uservin, "{'Text':{'Path':'CarVIN','Mode':'TwoWay'}}"}

            });

When I move from the lastname UITextView to the uservin UITextView I expect the SETTER in my viewmodel to get called, but it doesn't. When I click the button and check the value of the two text properties on my ViewModel, they are both null.

Does anybody know what I've done wrong? I've got a quick demo due on Tuesday and have all other platforms working beautifully, but just can't seem to get past this issue.

Cheers,

/j

回答1:

I think the problem will be that you are using UITextView instances... but mvvmcross vnext only ships with 2-way binding for UITextField elements.

To add the UITextView 2-way binding to an older mvvmcross version:

1. Add a custom target binding class - a bit like this one from v3: https://github.com/slodge/MvvmCross/blob/v3/Cirrious/Cirrious.MvvmCross.Binding.Touch/Target/MvxUITextViewTextTargetBinding.cs

2. Register it during Setup.cs with code like:

   protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry)
   {
       base.FillTargetFactories(registry);
   
       registry.RegisterFactory(new MvxSimplePropertyInfoTargetBindingFactory(typeof(MvxUITextViewTextTargetBinding), typeof(UITextView), "Text");
   }
   

---

Alternatively (but maybe not before your immediate demos), you could consider updating to the v3 beta release.

---

Incidentally, using the 'swiss' binding syntax is generally now the normal way to do this:

    this.AddBindings(
        new Dictionary<object, string>()
        {
            {lastname, "Text LastName"},
            {uservin, "Text CarVIN"}
        });

... and TwoWay binding is the default for most non-Windows MvvmCross bindings.

来源：https://stackoverflow.com/questions/15839310/how-do-i-do-two-way-binding-to-a-uitextview-control-using-mvvmcross