通过Windows 8 Metro XAML App下载并保存图片库中的图像

Question

我正在尝试开发一个简单的Windows8Metro应用程序，它只需从给定的网址(比如http://sample.com/foo.jpg)下载一个图像文件，然后将其保存到图片库。

我在UI中有一个图像控件来显示下载的图像。我还面临着将图像控件的图像源设置为新下载的图像的困难(实际上我甚至无法下载它)。

此外，是否可以将图像文件存储在Pictures库中的特定文件夹中(如果不存在，则应用程序应创建它)？

我真的被困在这里了。

请帮帮我。

Answer 1

这里有一些粗略的代码，我相信它们可以实现您想要的功能。它假设您有两个图像控件(Image1和Image2)，并且在清单中选中了Pictures Library功能。还可以看看XAML images sample

        Uri uri = new Uri("http://www.picsimages.net/photo/lebron-james/lebron-james_1312647633.jpg");
        var fileName = Guid.NewGuid().ToString() + ".jpg";

        // download pic
        var bitmapImage = new BitmapImage();
        var httpClient = new HttpClient();
        var httpResponse = await httpClient.GetAsync(uri);
        byte[] b = await httpResponse.Content.ReadAsByteArrayAsync();

        // create a new in memory stream and datawriter
        using (var stream = new InMemoryRandomAccessStream())
        {
            using (DataWriter dw = new DataWriter(stream))
            {
                // write the raw bytes and store
                dw.WriteBytes(b);
                await dw.StoreAsync();

                // set the image source
                stream.Seek(0);
                bitmapImage.SetSource(stream);

                // set image in first control
                Image1.Source = bitmapImage;

                // write to pictures library
                var storageFile = await KnownFolders.PicturesLibrary.CreateFileAsync(
                    fileName, 
                    CreationCollisionOption.ReplaceExisting);

                using (var storageStream = await storageFile.OpenAsync(FileAccessMode.ReadWrite))
                {
                    await RandomAccessStream.CopyAndCloseAsync(stream.GetInputStreamAt(0), storageStream.GetOutputStreamAt(0));
                }
            }
        }

        // read from pictures library
        var pictureFile = await KnownFolders.PicturesLibrary.GetFileAsync(fileName);
        using ( var pictureStream = await pictureFile.OpenAsync(FileAccessMode.Read) )
        {
            bitmapImage.SetSource(pictureStream);
        }
        Image2.Source = bitmapImage;
    }