如何在Windows Phone的页面之间传递照片？

Question

I know how to pass data through NavigationService.Navigate(new Uri("/Second.xaml?msg=mesage", UriKind.Relative));

The question is, how can I pass an image selected from the library to another page?

To select an image, I use the PhotoChooserTask and in the event where it is completed I have this:

 private void photoChooserTask_Completed(object sender, PhotoResult e)
    {
        if (e.ChosenPhoto != null)
        {
            BitmapImage image = new BitmapImage();
            image.SetSource(e.ChosenPhoto);
            this.img.Source = image;
        }
    }

How can I send the chosen photo to another page? Do I have to write it in a buffer, set a global variable or 'save' it in Isolated storage?

Answer 1

1. You could save your picture in IsolatedStorage first, pass the file path to another page as a string parameter, load the picture out when you need it.

2. Use PhoneApplicationService to save the image into State, load it when you need it.

Sample for saving into IsolatedStorage:

public static void SaveStreamToStorage(Stream imgStream, string fileName)
        {
            using (IsolatedStorageFile iso_storage = IsolatedStorageFile.GetUserStoreForApplication())
            {
                //Structure the path you want for your file.
                string filePath = GetImageStorePathByFileName(fileName);

                //Constants.S_STORE_PATH is the path I want to store my picture.
                if (!iso_storage.DirectoryExists(Constants.S_STORE_PATH))
                {
                    iso_storage.CreateDirectory(Constants.S_STORE_PATH);
                }
                //I skip the process when I find the same file.
                if (iso_storage.FileExists(filePath))
                {
                    return;
                }

                try
                {
                    if (imgStream.Length > 0)
                    {
                        using (IsolatedStorageFileStream isostream = iso_storage.CreateFile(filePath))
                        {
                            BitmapImage bitmap = new BitmapImage();
                            bitmap.SetSource(imgStream);

                            WriteableBitmap wb = new WriteableBitmap(bitmap);

                            // Encode WriteableBitmap object to a JPEG stream. 
                            Extensions.SaveJpeg(wb, isostream, wb.PixelWidth, wb.PixelHeight, 0, 100);

                            isostream.Close();

                            bitmap.UriSource = null;
                            bitmap = null;
                            wb = null;
                        }
                    }
                }
                catch(Exception e)
                {
                    if (iso_storage.FileExists(filePath))
                        iso_storage.DeleteFile(filePath);

                    throw e;
                }
            }
        }

Sample for reading picture from IsolatedStorage:

public static BitmapImage LoadImageFromIsolatedStorage(string imgName)
        {
            try
            {
                var bitmapImage = new BitmapImage();
                //bitmapImage.CreateOptions = BitmapCreateOptions.DelayCreation;
                using (var iso = IsolatedStorageFile.GetUserStoreForApplication())
                {
                    //Check if file exists to prevent exception when trying to access the file.
                    if (!iso.FileExists(GetImageStorePathByFileName(imgName)))
                    {
                        return null;
                    }
                    //Since I store my picture under a folder structure, I wrote a method GetImageStorePathByFileName(string fileName) to get the correct path.
                    using (var stream = iso.OpenFile(GetImageStorePathByFileName(imgName), FileMode.Open, FileAccess.Read))
                    {
                        bitmapImage.SetSource(stream);
                    }
                }
                //Return the picture as a bitmapImage
                return bitmapImage;
            }
            catch (Exception e)
            {
                // handle the exception 
                Debug.WriteLine(e.Message);
            }

            return null;
        }

Answer 2

You could use a variable defined in your app.xaml.cs and call it from your other page like so (don't mind the variable names, just a code sample I use for language support):

private LanguageSingleton LanguageInstance
{
    get
    {
        return (App.Current as App).Language;
    }
}

Here is how you could define that variable:

public LanguageSingleton Language { get; set; }

I'm sure there are more ways in doing this but this is one solution.