UWP - 如何將聯繫人縮略圖保存到本地存儲？

Question

我想一些幫助來獲得聯繫人的縮略圖並將其保存到本地存儲，我順利地拿到了接觸縮略圖，但我不能讓從流實際的形象，這是我的代碼：

var contactStore = await ContactManager.RequestStoreAsync(); 
var contacts = await contactStore.FindContactsAsync(); 
var myContact = contacts[0]; //I am sure that this Contact has a Thumbnail 

var stream = await myContact.Thumbnail.OpenReadAsync(); 
byte[] buffer = new byte[stream.Size]; 
var readBuffer = await stream.ReadAsync(buffer.AsBuffer(), (uint)buffer.Length, InputStreamOptions.None); 

var file = await ApplicationData.Current.LocalFolder.CreateFileAsync("image.jpg", CreationCollisionOption.ReplaceExisting); 
var fileStream = await file.OpenStreamForWriteAsync(); 
await fileStream.WriteAsync(readBuffer.ToArray(), 0, (int)readBuffer.Length); 

這段代碼在本地存儲中創建一個空的圖像，有幫助嗎？

感謝您的時間

Answer 1

這裏的問題是，你錯過了Stream.Flush method刷新緩衝區到底層的流。您可以在fileStream.WriteAsync方法之後添加fileStream.Flush();來解決您的問題。

除此之外，我們還需要撥打Stream.Dispose Method來釋放流在完成使用時所使用的資源。此方法通過將任何更改寫入後備存儲並關閉流釋放資源來處置流。所以我們可以在fileStream.WriteAsync方法之後使用fileStream.Dispose()。

一個建議的方式來調用Dispose方法是使用C＃使用聲明類似以下內容：

var contactStore = await ContactManager.RequestStoreAsync(); 
var contacts = await contactStore.FindContactsAsync(); 
var myContact = contacts[0]; //I am sure that this Contact has a Thumbnail 

using (var stream = await myContact.Thumbnail.OpenReadAsync()) 
{ 
    byte[] buffer = new byte[stream.Size]; 
    var readBuffer = await stream.ReadAsync(buffer.AsBuffer(), (uint)buffer.Length, InputStreamOptions.None); 

    var file = await ApplicationData.Current.LocalFolder.CreateFileAsync("image.jpg", CreationCollisionOption.ReplaceExisting); 
    using (var fileStream = await file.OpenStreamForWriteAsync()) 
    { 
     await fileStream.WriteAsync(readBuffer.ToArray(), 0, (int)readBuffer.Length); 
    } 
} 

Answer 2

我相信你可能需要調用stream.Dispose（）你從中讀取或者與using指令初始化流之後：using (var outputStream = stream.GetOutputStreamAt(0))

下面的鏈接可能是有用的： https://msdn.microsoft.com/en-us/windows/uwp/files/quickstart-reading-and-writing-files?f=255&MSPPError=-2147217396