一個接一個地調用兩個或多個函數

Question

我想調用兩個或更多個方法。當一個函數執行get完成時，我需要調用另一個方法。基本上我試圖在我的應用程序中實現備份功能。我正在開發Windows Phone應用程序，它需要備份聯繫人，圖像，視頻。我已經爲每個這些創建了方法。當聯繫人備份完成後，我想調用圖像方法。我爲這些創建了不同的功能。我怎樣才能一個接一個地調用這些函數？

我試過這樣的事情。

// Constructor 
    public MainPage() 
    { 
     InitializeComponent(); 

     UploadImagesThread = new Thread(UploadImages); 
     UploadContactsThread = new Thread(UploadContacts); 
     // Sample code to localize the ApplicationBar 
     //BuildLocalizedApplicationBar(); 
    } 

在上傳按鈕點擊

if (chkContacts.IsChecked.Value) 
{ 
    Dispatcher.BeginInvoke(() => 
    { 
     SystemTray.ProgressIndicator.Text = "Searching contacts..."; 
    }); 
    UploadContactsThread.Start(); 
} 
if (chkImages.IsChecked.Value) 
{ 
    Dispatcher.BeginInvoke(() => 
    { 
      SystemTray.ProgressIndicator.Text = "Compressing images..."; 
    }); 
    UploadImagesThread.Start(); 
} 

，但它不會幫助我。我如何充實？我UploadContact方法異步方法調用這樣

Contacts objContacts = new Contacts(); 
objContacts.SearchCompleted += new EventHandler<ContactsSearchEventArgs>(objContacts_SearchCompleted); 
objContacts.SearchAsync(string.Empty, FilterKind.None, null); 

Answer 1

嘗試使用任務，這將讓你給你一個線程池是免費的。你不能這樣做在一個構造函數，但你可以重寫你的OnNavigatedTo Mehtod：

protected override async void OnNavigatedTo(NavigationEventArgs e) 
    { 

     base.OnNavigatedTo(e); 

     await Task.Run(() => { UploadImages(); }); 
     await Task.Run(() => { UploadContacts(); }); 
    } 

的AWAIT將確保您的圖像完成後，觸點會開始上傳。您還可以查看background uploading這意味着您的應用在完成操作時無需運行。

Answer 2

使用Task.ContinueWith()來鎖定呼叫。你可以看看這裏：http://msdn.microsoft.com/de-de/library/dd321405(v=vs.110).aspx。

適用於您的問題，這應該做的伎倆：

Task.Factory.StartNew(UploadImages).ContinueWith(UploadContacts); 

Answer 3

您的問題（調用一個接一個的方法？）的描述不是很清楚，但看着你的代碼，我想您在開始UploadContactsThread之前等待UploadImagesThread線程完成。

使用任務和異步/等待關鍵字是這樣的：

private async void OnButtonClick(object sender, ...) 
{ 
    if (chkContacts.IsChecked.Value) 
    { 
     SystemTray.ProgressIndicator.Text = "Searching contacts..."; 
     await Task.Run(() => UploadImages()); 
    } 
    if (chkImages.IsChecked.Value) 
    { 
     SystemTray.ProgressIndicator.Text = "Compressing images..."; 
     await Task.Run(() => UploadContacts()); 
    } 
} 

注：假設你的代碼2號地塊在UI線程上運行，你不應該需要使用BeginInvoke。

---

編輯

針對最近的更改：你需要重新設計。試試這個：

private async void OnButtonClick(object sender, ...) 
{ 
    bool uploadContacts = chkContacts.IsChecked.Value; 
    bool uploadImages = chkImages.IsChecked.Value; 

    //use this if the continuation runs on the UI thread 
    Action continuation = async() => { 
    if(uploadImages) { 
     SystemTray.ProgressIndicator.Text = "Compressing images..."; 
     await Task.Run(() => UploadImages()); 
    } 
    }; 

    //OR this if it doesn't 
    Action continuation =() => { 
    if(uploadImages) { 
     Dispatcher.BeginInvoke(() => SystemTray.ProgressIndicator.Text = "Compressing images..."); 
     UploadImages(); 
    } 
    }; 

    if (uploadContacts) 
    { 
     SystemTray.ProgressIndicator.Text = "Searching contacts..."; 
     UploadContacts(continuation); 
    } 
} 

private void UploadContacts(Action continuation) 
{ 
    Contacts objContacts = new Contacts(); 

    //when the search has finished, trigger your event handler AND the continuation task, which will upload the images 
    objContacts.SearchCompleted += objContacts_SearchCompleted; 
    objContacts.SearchCompleted += (sender, args) => continuation(); 

    objContacts.SearchAsync(string.Empty, FilterKind.None, null); 
} 

Answer 4

嘗試類似的東西：

 bool backContact = chkContacts.IsChecked.Value; 
     bool backImages = chkImages.IsChecked.Value; 
     Task.Factory.StartNew(() => 
        { 
         if (backContact) { 
          Dispatcher.BeginInvoke(() => 
          { 
           SystemTray.ProgressIndicator.Text = "Searching contacts..."; 
          }); 
          UploadContacts; 
         }); 
        }).ContinueWith(() => 
         { 
          if (backImages) { 
           Dispatcher.BeginInvoke(() => 
          { 
           SystemTray.ProgressIndicator.Text = "Compressing images..."; 
          }); 
          UploadImages; 
          } 
         }