下载一个图像到Metro风格应用程序的本地存储 [英] Download an image to local storage in Metro style apps

问题描述

在的WinRT / C＃中，我怎样的图像下载到本地文件夹，支持在线目录脱机使用的缓存？有没有办法直接下载图像和链接控制从缓存中作为备用让他们？

In WinRT / C#, How do I download an image to a local folder to support caching of an online catalogue for offline use? is there a way to directly download the images and link the control to get them from the cache as a fallback?

    var downloadedimage = await HttpWebRequest.Create(url).GetResponseAsync();
    StorageFile imgfile = await ApplicationData.Current.LocalFolder.CreateFileAsync(
                        "localfile.png", CreationCollisionOption.FailIfExists);

我该怎么办旁边downloadedimage存储为localfile.jpg？

What do I do next to store downloadedimage as localfile.jpg?

推荐答案

看起来像是从HttpClient的样本下面的代码为Windows 8解决问题。

Looks like the code below from the HttpClient sample for Windows 8 solves the issue

    HttpRequestMessage request = new HttpRequestMessage(
        HttpMethod.Get, resourceAddress);
    HttpResponseMessage response = await rootPage.httpClient.SendAsync(request,
        HttpCompletionOption.ResponseHeadersRead);

HttpClient的是一个HttpClient和其BaseAddress需要设置你的资源的服务器文件夹。那么我们可以做到这一点将其转换成图像源（如果那是我们正在下载的）

httpClient is a HttpClient, and its BaseAddress needs to be set a the server folder of your resource. we can then do this to convert that to an image source (if that's what we're downloading)

    InMemoryRandomAccessStream randomAccessStream = 
        new InMemoryRandomAccessStream();
    DataWriter writer = new DataWriter(randomAccessStream.GetOutputStreamAt(0));
    writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());
    await writer.StoreAsync();
    BitmapImage image = new BitmapImage();
    imagecontrol.SetSource(randomAccessStream);

或此写入到文件

    var imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(
         filename, CreationCollisionOption.ReplaceExisting);
    var fs = await imageFile.OpenAsync(FileAccessMode.ReadWrite);
    DataWriter writer = new DataWriter(fs.GetOutputStreamAt(0));
    writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());
    await writer.StoreAsync();
    writer.DetachStream();
    await fs.FlushAsync();

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