AnimatedStackVisibilityTargetBinding.cs

using System;
using Foundation;
using MvvmCross.Binding;
using MvvmCross.Binding.Bindings.Target.Construction;
using MvvmCross.Binding.iOS.Target;
using MvvmCross.Platform.UI;
using UIKit;

namespace Vapolia.Ios.Lib.MvxUi
{
    /// <summary>
    /// Animates visibility of views that are subviews of a StackView.
    /// Uses the StackView's ability to animate the change of the 'Hidden' property.
    /// 
    /// Sample usage
    /// set.Bind(NoDeviceContainer).For(AnimatedStackVisibilityTargetBinding.Name).To(vm => vm.IsStateDisabled).WithConversion("Visibility");
    ///
    /// Note that performances are very bad with 5 animated items: there is a kind of "pause" before animations really starts.
    /// If someone finds why ...
    /// </summary>
    [Preserve]
    public class AnimatedStackVisibilityTargetBinding : MvxUIViewVisibilityTargetBinding
    {
        public const string Name = "AnimatedStackVisibility";

        [Preserve]
        public AnimatedStackVisibilityTargetBinding(UIView target) : base(target)
        {
        }

        public static void Register(IMvxTargetBindingFactoryRegistry registry)
        {
            registry.RegisterCustomBindingFactory<UIView>(Name, view => new AnimatedStackVisibilityTargetBinding(view));
        }

        [Preserve]
        public override Type TargetType => typeof(UIView);

        [Preserve]
        public override MvxBindingMode DefaultMode => MvxBindingMode.OneWay;

        [Preserve]
        protected override void SetValueImpl(object target, object value)
        {
            var view = target as UIView;
            if (view == null)
                return;

            var visible = (MvxVisibility) value == MvxVisibility.Visible; //value.ConvertToBoolean();

            ////Disable animation when view is bound after a cell reuse
            //if (view.Tag == 1)
            //{
            //    view.Tag = 0;
            //    view.Alpha = visible == MvxVisibility.Visible ? 1 : 0;
            //    return;
            //}

            if (!UIView.AnimationsEnabled)
            {
                view.Hidden = !visible;
                view.Alpha = visible ? 1 : 0;
            }
            else
            {
                UIView.Animate(.4, () =>
                {
                    view.Hidden = !visible;
                    view.Alpha = visible ? 1 : 0;
                });
            }
        }
    }
}