iOS Animated Image View. Display GIFs on iOS. Ported from: https://github.com/atnan/UIImageView-NDVAnimatedGIFSupport/blob/master/UIImageView%2BNDVAnimatedGIFSupport.m

AnimatedImageView.cs

using System.Collections.Generic;
using System.Drawing;
using MonoTouch.CoreAnimation;
using MonoTouch.CoreGraphics;
using MonoTouch.Foundation;
using MonoTouch.ImageIO;
using MonoTouch.UIKit;

namespace PuppyKittyOverflow.Touch
{
    public class AnimatedImageView
    {
        public static UIImageView GetAnimatedImageView(string url, UIImageView imageView = null)
        {
            var sourceRef = CGImageSource.FromUrl(NSUrl.FromString(url));
			return CreateAnimatedImageView (sourceRef, imageView);

        }

        public static UIImageView GetAnimatedImageView(NSData nsData, UIImageView imageView = null)
        {

			var sourceRef = CGImageSource.FromData(nsData);

            return CreateAnimatedImageView(sourceRef, imageView);
        }

        private static UIImageView CreateAnimatedImageView(CGImageSource imageSource, UIImageView imageView = null)
        {
            var frameCount = imageSource.ImageCount;

            var frameImages = new List<NSObject>(frameCount);
            var frameCGImages = new List<CGImage>(frameCount);
            var frameDurations = new List<double>(frameCount);

            var totalFrameDuration = 0.0;

            for (int i = 0; i < frameCount; i++)
            {
                var frameImage = imageSource.CreateImage(i, null);

                frameCGImages.Add(frameImage);
                frameImages.Add(NSObject.FromObject(frameImage));

                var properties = imageSource.GetProperties(i, null);
                var duration = properties.Dictionary["{GIF}"];
                var delayTime = duration.ValueForKey(new NSString("DelayTime"));
				duration.Dispose ();
                var realDuration = double.Parse(delayTime.ToString());
                frameDurations.Add(realDuration);
                totalFrameDuration += realDuration;
				frameImage.Dispose ();
            }

            var framePercentageDurations = new List<NSNumber>(frameCount);
            var framePercentageDurationsDouble = new List<double>(frameCount);
            NSNumber currentDurationPercentage = 0.0f;
            double currentDurationDouble = 0.0f;
            for (int i = 0; i < frameCount; i++)
            {
                if (i != 0)
                {
                    var previousDuration = frameDurations[i - 1];
                    var previousDurationPercentage = framePercentageDurationsDouble[i - 1];

                    var number = previousDurationPercentage + (previousDuration/totalFrameDuration);
                    currentDurationDouble = number;
                    currentDurationPercentage = new NSNumber(number);
                }
                framePercentageDurationsDouble.Add(currentDurationDouble);
                framePercentageDurations.Add(currentDurationPercentage);
            }

            var imageSourceProperties = imageSource.GetProperties(null);
            var imageSourceGIFProperties = imageSourceProperties.Dictionary["{GIF}"];
            var loopCount = imageSourceGIFProperties.ValueForKey(new NSString("LoopCount"));
            var imageSourceLoopCount = float.Parse(loopCount.ToString());
            var frameAnimation = new CAKeyFrameAnimation();
            frameAnimation.KeyPath = "contents";
            if (imageSourceLoopCount <= 0.0f)
            {
                frameAnimation.RepeatCount = float.MaxValue;
            }
            else
            {
                frameAnimation.RepeatCount = imageSourceLoopCount;
            }

			imageSourceGIFProperties.Dispose ();


            frameAnimation.CalculationMode = CAAnimation.AnimationDescrete;
            frameAnimation.Values = frameImages.ToArray();
            frameAnimation.Duration = totalFrameDuration;
            frameAnimation.KeyTimes = framePercentageDurations.ToArray();
            frameAnimation.RemovedOnCompletion = false;
            var firstFrame = frameCGImages[0];
            if(imageView == null)
                imageView = new UIImageView(new RectangleF(0.0f, 0.0f, firstFrame.Width, firstFrame.Height));
            else
                imageView.Layer.RemoveAllAnimations();

            imageView.Layer.AddAnimation(frameAnimation, "contents");

			frameAnimation.Dispose ();
            return imageView;
        }
    }
}

Usage

var client = new HttpClient();
var stream = await client.GetStreamAsync(image);
var data = await GetDataAsync(stream);
AnimatedImageView.GetAnimatedImageView(data, ImageViewAnimal);


private async Task<NSData> GetDataAsync(Stream stream)
{
  return await Task.Run (() =>  {return NSData.FromStream (stream);});
}

Be aware that this class leads to very huge memory leaks. CGImage is not memory managed and if you don't manually remove the animateView the memory continues to increase without any limit. You can easily see this with the apple profiler

I have jus learnt this after 3 days of troubleshooting !