WinRt - FileSavePicker，将图像从URI保存到文件

Question

我想问如何保存图像从一个流到另一个文件。我已经创建了这个FileSavePicker，但是我不知道如何从Uri中保存图像

谢谢

  StreamReader reader = new StreamReader(dataStream);
                // Read the content.
               string responseFromServer = reader.ReadLine(); // URi with image


 private async void saveClick(object sender, RoutedEventArgs e)
    {
       var Picker = new FileSavePicker();
       Picker.FileTypeChoices.Add("Image", new List<string>() { ".jpg" });
       StorageFile file = await Picker.PickSaveFileAsync();



    }

Answer 1

我想您已经将图像下载到dataStream中了。如果不是，您可以使用HttpClient类这样做：

var uri = new Uri("http://cdn.sstatic.net/stackexchange/img/logos/so/so-logo-med.png");
Windows.Web.Http.HttpClient httpClient = new HttpClient();
var stream = await httpClient.GetInputStreamAsync(uri);
Stream dataStream = stream.AsStreamForRead();

您可以通过在OpenStreamForWriteAsync上调用StorageFile来获取可写入的流到所选文件。使用两个流，您可以调用CopyTo从dataStream复制到保存流。

var Picker = new FileSavePicker();
Picker.FileTypeChoices.Add("Image", new List<string>() { ".jpg" });
StorageFile file = await Picker.PickSaveFileAsync();
using (Stream saveStream = await file.OpenStreamForWriteAsync())
{
    dataStream.Seek(0, SeekOrigin.Begin);
    await dataStream.CopyToAsync(saveStream);
}