mvvmcross : Bind a static RadioGroup using zero based indexes

MvxRadioGroupSelectedIndexBinding.cs

    /// <summary>
    /// Author: softlion (softlion@softlion.com)
    /// </summary>
    /// <remarks>
    /// Thanks to: Stuart Lodge
    /// </remarks>
    public class MvxRadioGroupSelectedIndexBinding : MvxAndroidTargetBinding
    {
        bool stopListeningCheckChanged = false;

        private int selectedIndex = -2;
        public int SelectedIndex
        { 
            get { return selectedIndex; }
            set { if(value != selectedIndex) { selectedIndex = value; FireValueChanged(SelectedIndex); } }
        }
        
        public static void Register(IMvxTargetBindingFactoryRegistry registry)
        {
            registry.RegisterCustomBindingFactory<RadioGroup>("SelectedIndex", radioGroup => new MvxRadioGroupSelectedIndexBinding(radioGroup));
        }

        public MvxRadioGroupSelectedIndexBinding(RadioGroup radioGroup) : base(radioGroup)
        {
            if (radioGroup == null)
            {
                Mvx.Trace(MvxTraceLevel.Error, "RadioGroup SelectedIndex: radioGroup is null");
                return;
            }

            radioGroup.CheckedChange += CheckedChange;
            radioGroup.ChildViewAdded += RadioGroupOnChildViewAdded;
            //radioGroup.ChildViewRemoved += RadioGroupOnChildViewRemoved;
        }

        private void RadioGroupOnChildViewAdded(object sender, ViewGroup.ChildViewAddedEventArgs childViewAddedEventArgs)
        {
            var radioGroup = Target as RadioGroup;
            if (selectedIndex == radioGroup.ChildCount-1)
            {
                stopListeningCheckChanged = true;
                radioGroup.Check(radioGroup.GetChildAt(selectedIndex).Id);
                stopListeningCheckChanged = false;
            }
        }

        //private void RadioGroupOnChildViewRemoved(object sender, ViewGroup.ChildViewRemovedEventArgs childViewRemovedEventArgs)
        //{
        //    ChildViewCountChanged();
        //}

        private void CheckedChange(object sender, RadioGroup.CheckedChangeEventArgs e)
        {
            if (stopListeningCheckChanged)
                return;

            var radioGroup = Target as RadioGroup;
            var checkedId = e.CheckedId;

            if (checkedId == View.NoId)
            {
                SelectedIndex = -1;
                return;
            }

            for (var i = radioGroup.ChildCount - 1; i >= 0; i--)
            {
                if (checkedId == radioGroup.GetChildAt(i).Id)
                {
                    SelectedIndex = i;
                    return;
                }
            }
            SelectedIndex = -1;
            Mvx.Trace(MvxTraceLevel.Error, "RadioGroup id not found: {0}", checkedId);
        }

        public override void SetValue(object index)
        {
            var radioGroup = Target as RadioGroup;
            if (radioGroup == null)
                return;

            stopListeningCheckChanged = true;
            selectedIndex = (int)index;
            if (selectedIndex < 0 || selectedIndex >= radioGroup.ChildCount)
            {
                radioGroup.ClearCheck();
                //selectedIndex = -1;
            }
            else
            {
                radioGroup.Check(radioGroup.GetChildAt(selectedIndex).Id);
                //selectedIndex = newIndex;
            }
            stopListeningCheckChanged = false;
        }

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

        protected override void SetValueImpl(object target, object value)
        {
        }

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

        protected override void Dispose(bool isDisposing)
        {
            if (isDisposing)
            {
                var radioGroup = Target as RadioGroup;
                if (radioGroup != null)
                {
                    radioGroup.CheckedChange -= CheckedChange;
                    radioGroup.ChildViewAdded -= RadioGroupOnChildViewAdded;
                    //radioGroup.ChildViewRemoved -= ChildViewCountChanged;
                }
            }
            base.Dispose(isDisposing);
        }
    }

usage.axml

        <RadioGroup
            android:orientation="horizontal"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            local:MvxBind="SelectedIndex YourIntegerProperty">
            <RadioButton
                android:text="first"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
            <RadioButton
                android:text="last"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </RadioGroup>
        

Thanks, works like a charm!

It's exactly that I need, thank you!