Mvvmcross bind to Visibility with autolayout and f

问题:

Currently binding to "Visibility" sets Hidden=true. How would you create a generic Visibility binding which also changes a constraint: sets the view height to 0 ?

回答1:

For a tutorial on creating bindings, see the N=28 video on http://mvvmcross.blogspot.com/

To replace the existing visibility binding, simply create your own class based on https://github.com/MvvmCross/MvvmCross/blob/v3.1/Cirrious/Cirrious.MvvmCross.Binding.Touch/Target/MvxUIViewVisibleTargetBinding.cs

public class MyUIViewVisibleTargetBinding : MvxBaseUIViewVisibleTargetBinding
{
    public MyUIViewVisibleTargetBinding(UIView target)
        : base(target)
    {
    }

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

        var visible = value.ConvertToBoolean();
        // your code here
        // - in place of or in addition to:
        // view.Hidden = !visible;
    }
}

And register this as the last step in Setup using:

protected override void InitializeLastChance()
{
     base.InitializeLastChance();

     var registry = Mvx.Resolve<IMvxTargetBindingFactoryRegistry>();
     registry.RegisterCustomBindingFactory<UIView>("Visible",
                                                    view =>
                                                    new MyUIViewVisibleTargetBinding(view));

}

For more on replacing existing bindings, see MVVMCross Binding decimal to UITextField removes decimal point

---

Note that if you want to replace all Visible bindings, then you might want to replace all of Visible, Visibility and Hidden - see registrations in https://github.com/MvvmCross/MvvmCross/blob/v3.1/Cirrious/Cirrious.MvvmCross.Binding.Touch/MvxTouchBindingBuilder.cs#L42