Binding views to ICommand.CanExecute - mvvmcross

Question

Is it somehow possible to bind view properties to ICommand.CanExecute?
I'd for example like to be able to do something like this in a touch view:
this
.CreateBinding(SignInWithFacebookButton)
.For(b => b.Enabled)
.To((SignInViewModel vm) => vm.SignInWithFacebookCommand.CanExecute)
.Apply();
I've already read How to use CanExecute with Mvvmcross, but unfortunately it skips the questions and instead just proposes another implementation.

Answer 1

One way of doing this is to use your own custom button inheriting from UIButton.
For Android, I've got an implementation of this to hand - it is:
public class FullButton : Button
{
protected FullButton(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
{
Click += OnClick;
}
public FullButton(Context context) : base(context)
{
Click += OnClick;
}
public FullButton(Context context, IAttributeSet attrs) : base(context, attrs)
{
Click += OnClick;
}
public FullButton(Context context, IAttributeSet attrs, int defStyle) : base(context, attrs, defStyle)
{
Click += OnClick;
}
private IDisposable _subscription;
private object _commandParameter;
public object CommandParameter
{
get { return _commandParameter; }
set
{
_commandParameter = value;
UpdateEnabled();
}
}
private ICommand _command;
public ICommand Command
{
get { return _command; }
set
{
if (_subscription != null)
{
_subscription.Dispose();
_subscription = null;
}
_command = value;
if (_command != null)
{
var cec = typeof (ICommand).GetEvent("CanExecuteChanged");
_subscription = cec.WeakSubscribe(_command, (s, e) =>
{
UpdateEnabled();
});
}
UpdateEnabled();
}
}
private void OnClick(object sender, EventArgs eventArgs)
{
if (Command == null)
return;
if (Command.CanExecute(CommandParameter))
Command.Execute(CommandParameter);
}
private void UpdateEnabled()
{
Enabled = ShouldBeEnabled();
}
private bool ShouldBeEnabled()
{
if (_command == null)
return false;
return _command.CanExecute(CommandParameter);
}
}
and this can be bound as:
<FullButton
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Show Detail"
local:MvxBind="Command ShowDetailCommand; CommandParameter CurrentItem" />
For iOS, I'd expect the same type of technique to work... inheriting from a UIButton and using TouchUpInside instead of Click - but I'm afraid I don't have this code with me at the moment.