UrlImageViewHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.Graphics.Drawables;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;

namespace UrlImageViewHelper
{
	public class UrlImageViewHelper
	{
		public const string LOGTAG = "UrlImageViewHelper";
		public const int CACHE_DURATION_INFINITE = int.MaxValue;
    	public const int CACHE_DURATION_ONE_DAY = 1000 * 60 * 60 * 24;
    	public const int CACHE_DURATION_TWO_DAYS = CACHE_DURATION_ONE_DAY * 2;
    	public const int CACHE_DURATION_THREE_DAYS = CACHE_DURATION_ONE_DAY * 3;
    	public const int CACHE_DURATION_FOUR_DAYS = CACHE_DURATION_ONE_DAY * 4;
    	public const int CACHE_DURATION_FIVE_DAYS = CACHE_DURATION_ONE_DAY * 5;
    	public const int CACHE_DURATION_SIX_DAYS = CACHE_DURATION_ONE_DAY * 6;
    	public const int CACHE_DURATION_ONE_WEEK = CACHE_DURATION_ONE_DAY * 7;

		public static void SetUrlDrawable(ImageView imageView, string url, int defaultResource)
		{
			SetUrlDrawable(imageView.Context, imageView, url, defaultResource, CACHE_DURATION_THREE_DAYS);
		}

		public static void SetUrlDrawable(ImageView imageView, string url)
		{
			SetUrlDrawable(imageView.Context, imageView, url, null, CACHE_DURATION_THREE_DAYS, null);
		}

		public static void LoadDrawable(Context context, string url)
		{
			 SetUrlDrawable(context, null, url, null, CACHE_DURATION_THREE_DAYS, null);
		}

		public static void SetUrlDrawable(ImageView imageView, string url, Drawable defaultDrawable)
		{
			SetUrlDrawable(imageView.Context, imageView, url, defaultDrawable, CACHE_DURATION_THREE_DAYS, null);
		}

		public static void SetUrlDrawable(ImageView imageView, string url, int defaultResource, long cacheDurationMs)
		{
			SetUrlDrawable(imageView.Context, imageView, url, defaultResource, cacheDurationMs);
		}

		public static void LoadUrlDrawable(Context context, string url, long cacheDurationMs)
		{
			SetUrlDrawable(context, null, url, null, cacheDurationMs, null);
		}

		public static void SetUrlDrawable(ImageView imageView, string url, Drawable defaultDrawable, long cacheDurationMs)
		{
			SetUrlDrawable(imageView.Context, imageView, url, defaultDrawable, cacheDurationMs, null);
		}

		private static void SetUrlDrawable(Context context, ImageView imageView, string url, int defaultResource, long cacheDurationMs)
		{
			Drawable d = null;
			if (defaultResource != 0)
				d = imageView.Resources.GetDrawable(defaultResource);
			SetUrlDrawable(context, imageView, url, d, cacheDurationMs, null);
		}

		public static void SetUrlDrawable(ImageView imageView, string url, IUrlImageViewCallback callback) 
		{
        	SetUrlDrawable(imageView.Context, imageView, url, null, CACHE_DURATION_THREE_DAYS, callback);
	    }

	    public static void LoadUrlDrawable(Context context, string url, IUrlImageViewCallback callback) 
		{
	        SetUrlDrawable(context, null, url, null, CACHE_DURATION_THREE_DAYS, callback);
	    }

	    public static void SetUrlDrawable(ImageView imageView, string url, Drawable defaultDrawable, IUrlImageViewCallback callback) 
		{
	        SetUrlDrawable(imageView.Context, imageView, url, defaultDrawable, CACHE_DURATION_THREE_DAYS, callback);
	    }

	    public static void SetUrlDrawable(ImageView imageView, string url, int defaultResource, long cacheDurationMs, IUrlImageViewCallback callback) 
		{
	        SetUrlDrawable(imageView.Context, imageView, url, defaultResource, cacheDurationMs, callback);
	    }

	    public static void LoadUrlDrawable(Context context, string url, long cacheDurationMs, IUrlImageViewCallback callback) 
		{
	        SetUrlDrawable(context, null, url, null, cacheDurationMs, callback);
	    }

	    public static void SetUrlDrawable(ImageView imageView, string url, Drawable defaultDrawable, long cacheDurationMs, IUrlImageViewCallback callback) 
		{
	        SetUrlDrawable(imageView.Context, imageView, url, defaultDrawable, cacheDurationMs, callback);
	    }

	    private static void SetUrlDrawable(Context context, ImageView imageView, string url, int defaultResource, long cacheDurationMs, IUrlImageViewCallback callback) 
		{
	        Drawable d = null;
	        if (defaultResource != 0)
				d = imageView.Resources.GetDrawable(defaultResource);
	        SetUrlDrawable(context, imageView, url, d, cacheDurationMs, callback);
	    }

		protected static HashTable<ImageView, string> pendingViews = new HashTable<ImageView, string>();
		protected static HashTable<string, List<ImageView>> pendingDownloads = new HashTable<string, List<ImageView>>();
		static bool hasCleaned = false;

		static Android.Content.Res.Resources mResources;
    	static Android.Util.DisplayMetrics mMetrics;
	    
		private static void PrepareResources(Context context) 
		{
	        if (mMetrics != null)
	            return;
			mMetrics = new Android.Util.DisplayMetrics();
	        Activity act = (Activity)context;
			act.WindowManager.DefaultDisplay.GetMetrics(mMetrics);
			var mgr = context.Assets;
	        mResources = new Android.Content.Res.Resources(mgr, mMetrics, context.Resources.Configuration);
	    }

	    public static BitmapDrawable LoadDrawableFromFile(Context context, string filename) 
		{
	        PrepareResources(context);
	        
			var bitmap = Android.Graphics.BitmapFactory.DecodeFile(filename);

			//var bitmap = Android.Graphics.BitmapFactory.DecodeStream(stream);
	        //Log.i(LOGTAG, String.format("Loaded bitmap (%dx%d).", bitmap.getWidth(), bitmap.getHeight()));
	        return new BitmapDrawable(mResources, bitmap);
	    }

		private static void Cleanup(Context context)
		{
			if (hasCleaned)
				return;

			hasCleaned = true;

			try
			{
				var baseDir = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);

				var files = System.IO.Directory.GetFiles(baseDir);

				if (files == null || files.Length <= 0)
					return;

				foreach (var file in files)
				{
					if (!file.EndsWith(".urlimage"))
						continue;

					
					var f = new System.IO.FileInfo(file);
					if (DateTime.UtcNow > f.LastWriteTimeUtc)
						f.Delete();
				}
			}
			catch { }
		}

		private static string GetFilenameForUrl(string url)
		{
			var hashCode = url.GetHashCode().ToString().Replace("-", "N");
			return hashCode + ".urlimage";
		}

		private static void SetUrlDrawable(Context context, ImageView imageView, string url, Drawable defaultDrawable, long cacheDurationMs, IUrlImageViewCallback callback)
		{
			Cleanup(context);

			if (imageView != null)
				pendingViews.Remove(imageView);

			if (string.IsNullOrEmpty(url))
			{
				if (imageView != null)
					imageView.SetImageDrawable(defaultDrawable);

				return;
			}

			var cache = UrlImageCache.Instance;
			var drawable = cache.Get(url);

			if (drawable != null)
			{
				if (imageView != null)
					imageView.SetImageDrawable(drawable);
				if (callback != null)
					callback.OnLoaded(imageView, drawable, url, true);
				return;
			}

			var baseDir = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
			var filename = System.IO.Path.Combine(baseDir, GetFilenameForUrl(url));
					
			var file = new System.IO.FileInfo(filename);
			if (file.Exists)
			{
				try
				{
					if (cacheDurationMs == CACHE_DURATION_INFINITE || DateTime.UtcNow < file.LastWriteTimeUtc.AddMilliseconds(cacheDurationMs))
					{
						drawable = LoadDrawableFromFile(context, filename);
						//var fis = context.OpenFileInput(filename);
						//drawable = LoadDrawableFromStream(context, fis);
						//fis.Close();

						if (imageView != null)
							imageView.SetImageDrawable(drawable);

						cache.Put(url, drawable);

						if (callback != null)
							callback.OnLoaded(imageView, drawable, url, true);

						return;
					}
					else
					{
						//TODO: File cache expired, refreshing
						Android.Util.Log.Debug(LOGTAG, "File Cache Expired: " + file.Name);
					}
				}
				catch (Exception ex)
				{
					Android.Util.Log.Debug(LOGTAG, "File Cache Exception " + ex.ToString());
				}
			}

			if (imageView != null)
				imageView.SetImageDrawable(defaultDrawable);

			if (imageView != null)
				pendingViews.Put(imageView, url);

			//Check to see if another view is already waiting for this url so we don't download it again
			var currentDownload = pendingDownloads.Get(url);
			if (currentDownload != null)
			{
				if (imageView != null)
					currentDownload.Add(imageView);

				return;
			}

			var downloads = new List<ImageView>();
			if (imageView != null)
				downloads.Add(imageView);

			pendingDownloads.Put(url, downloads);

			var downloaderTask = new AnonymousAsyncTask<string, string, BitmapDrawable>((p) => 
			{
				try
				{
					var client = new System.Net.WebClient();
					var data = client.DownloadData(url);

					System.IO.File.WriteAllBytes(filename, data);

					return LoadDrawableFromFile(context, filename);
				}
				catch (Exception ex) 
				{
					Android.Util.Log.Debug(LOGTAG, "Download Error: " + ex.ToString());
					return null; 
				}


			}, (bd) => 
			{
				try
				{
					var usableResult = bd;
					if (usableResult == null)
						usableResult = (BitmapDrawable)defaultDrawable;

					pendingDownloads.Remove(url);

					cache.Put(url, usableResult);

					foreach (var iv in downloads)
					{
						var pendingUrl = pendingViews.Get (iv);
						if (!url.Equals(pendingUrl))
							continue;
						pendingViews.Remove(iv);

						if (usableResult != null)
						{
							var fnewImage = usableResult;
							var fimageView = iv;

							fimageView.SetImageDrawable(fnewImage);

							if (callback != null)
								callback.OnLoaded(fimageView, bd, url, false);
						}
					}
				}
				catch (Exception ex)
				{
					Android.Util.Log.Debug(LOGTAG, "PostExecute Error: " + ex.ToString()); 
				}

			});

			downloaderTask.Execute(new Java.Lang.Object[]{});
		}
	}
}