Save and Load image from Isolated Storage (Windows Phone)

Question

I have found a very usefull class on this link: images caching - that help me to make logic for caching images. But in my case I have this:

 private void DetailView_SelectionChanged(object sender, SelectionChangedEventArgs e)
            {
                                   SaveAndLoadImage(feedItem);


            }

And in this method I save and load image from isolated storage. But I can't load file imidiately because of some permission (Operation not permitted on IsolatedStorageFileStream.). How can I correct my logic to save and load images immediately?

  public void SaveAndLoadImage(MediaItemViewModel curItem)
            {
                string url = string.Empty;
                if (!string.IsNullOrEmpty(curItem.ThumbUrl))
                {
                    url = curItem.ThumbUrl;
                }
                if ((string.IsNullOrEmpty(curItem.ThumbUrl)) && (!string.IsNullOrEmpty(curItem.MediaUrl)))
                {
                    url = curItem.MediaUrl;
                }
                if ((!string.IsNullOrEmpty(url)) && (CacheImageFile.GetInstance().IsOnStorage(new Uri(url)) == false))
                {
                    CacheImageFile.DownloadFromWeb(new Uri(url));

                }

                    curItem.ImageSource = CacheImageFile.ExtractFromLocalStorage(new Uri(url)) as BitmapImage;

            }

Answer 1

You can use JetImageLoader, I created it for application, where we need to load, cache and show big amount of logos, icons and so on.

It can be used as binding converter, so you should not even change your code! Just update your XAMLs!

Please, check out samples in repository, you'll love it ;)

Features:

• Caching on disk
• Caching in memory
• Fully asynchronous
• Available as binding converter or programmatically from your code
• Fully open source, fork and improve it!

Here is the example:

<Image Source="{Binding ImageUrl, Converter={StaticResource MyAppJetImageLoaderConverter}}"/>

P.S. I am sorry, that I copying my answer from another questions, but image caching on windows phone is huge problem and I want to share my solution, so everybody can use it and improve for developers community

Answer 2

You are getting the image asynchronously from the web, but immediately go to the next line to read the file that hasn't even been written to isolated storage. This is what's causing you the exception.

You could try editing the caching library you found on github, using ManualResetEvent. Notice that you will have to make the method calls on another thread!

For example:

public class CacheImageFileConverter : IValueConverter
{
    ...
    private static ManualResetEvent mre = new ManualResetEvent(true);

    private static object DownloadFromWeb(Uri imageFileUri)
    {
        mre.Reset();
        WebClient m_webClient = new WebClient();                                //Load from internet
        BitmapImage bm = new BitmapImage();

        m_webClient.OpenReadCompleted += (o, e) =>
        {
            if (e.Error != null || e.Cancelled) return;
            WriteToIsolatedStorage(IsolatedStorageFile.GetUserStoreForApplication(), e.Result, GetFileNameInIsolatedStorage(imageFileUri));
            bm.SetSource(e.Result);
            e.Result.Close();
            mre.Set();
        };
        m_webClient.OpenReadAsync(imageFileUri);
        return bm;
    }

    private static object ExtractFromLocalStorage(Uri imageFileUri)
    {
        mre.WaitOne();
        string isolatedStoragePath = GetFileNameInIsolatedStorage(imageFileUri);       //Load from local storage
        using (var sourceFile = _storage.OpenFile(isolatedStoragePath, FileMode.Open, FileAccess.Read))
        {
            BitmapImage bm = new BitmapImage();
            bm.SetSource(sourceFile);
            return bm;
        }
    }
    .... other methods
}

Notice the use of Reset, Set and WaitOne for signaling.

Answer 3

have a look at below link

http://www.windowsphonegeek.com/tips/All-about-WP7-Isolated-Storage---Read-and-Save-Images

for loading images from isolated storage. using streams

BitmapImage bi = new BitmapImage();

            using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (IsolatedStorageFileStream fileStream = myIsolatedStorage.OpenFile("logo.jpg", FileMode.Open, FileAccess.Read))
                {
                    bi.SetSource(fileStream);
                    this.img.Height = bi.PixelHeight;
                    this.img.Width = bi.PixelWidth;
                }
            }
            this.img.Source = bi;