Binding 'GO' key on Software Keyboard

Question

I've got a log-in button bound to a command that exists inside my ViewModel like so:

this.AddBindings(new Dictionary<object, string>{{btnLogin,"TouchUpInside LoginCommand"}});

The software keyboard is suppressed if a touch is made, somewhere outside the keyboard or UITextField. To prevent the user from having to click once somewhere on the screen to make the keyboard disappear and then pressing the log-in button, I would like to associate the log-in command defined in the ViewModel to the 'GO' key in the keyboard. Is this possible?

Answer 1

The simple solution is the one given in the previous answer.

However, if you wanted to go further, then you could add a custom binding, implemented something like:

public class MvxUITextFieldShouldReturnTargetBinding
    : MvxTargetBinding
{
    private ICommand _command;

    protected UITextField View
    {
        get { return Target as UITextField; }
    }

    public MvxUITextFieldShouldReturnTargetBinding(UITextField target)
        : base(target)
    {
        target.ShouldReturn = HandleShouldReturn;
    }

    private bool HandleShouldReturn(UITextField textField)
    {
        if (_command == null)
            return false;

        var text = textField.Text;
        if (!_command.CanExecute(text))
            return false;

        textField.ResignFirstResponder();
        _command.Execute(text);
        return true;
    }

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

    public override void SetValue(object value)
    {
        var command = value as ICommand;
        _command = command;
    }

    public override System.Type TargetType
    {
        get { return typeof(ICommand); }
    }


    protected override void Dispose(bool isDisposing)
    {
        base.Dispose(isDisposing);
        if (isDisposing)
        {
            var editText = View;
            if (editText != null)
            {
                editText.ShouldReturn = null;
            }
        }
    }
}

which you could register during setup as:

        registry.RegisterCustomBindingFactory<UITextField>("ShouldReturn",
                                                           textField => new MvxUITextFieldShouldReturnTargetBinding(textField));

I think that would work - it should allow you to bind a MvxCommand or an MvxCommand<string>

For more on custom bindings, see N=28 in http://mvvmcross.wordpress.com