暫停的AsyncTask執行，基於用戶輸入提示用戶輸入並繼續執行

Question

我有以下AsyncTask

public class LoadFromCloudTask extends AsyncTask<Void, String, Boolean> { 

    public LoadFromCloudTask(LoadFromCloudTaskFragment loadFromCloudTaskFragment) { 
     this.loadFromCloudTaskFragment = loadFromCloudTaskFragment; 
    } 

    @Override 
    protected Boolean doInBackground(Void... params) { 
     ... 
     ... 
     ... 
     // How possible I can halt my execution, prompt for user input, and continue execution based on user input. 
     // In Swing, I can ... 
     // 
     /* 
      // Hold the execution, and prompt for user input 
      final int result = JOptionPane.showConfirmDialog(LoadFromCloudJDialog.this, message, MessagesBundle.getString("question_title_overwrite_your_data_by_cloud_data_at"), JOptionPane.YES_NO_OPTION); 
      // Continue execution based on user input. 
     */ 
    } 
} 

我想知道，是否有可能停止的AsyncTask執行，提示用戶輸入並繼續基於執行在用戶輸入？

在Swing中，我可以通過簡單地使用JOptionPane.showConfirmDialog來實現此目的。 Android如何？

Answer 1

由於doInBackground執行在不同的線程，你必須暫停這個線程，同時顯示在UI線程一些dialog，一旦該對話框駁回你可以恢復AsyncTask和讀取結果。

Answer 2

檢查Asynctask的文檔，你可以取消並重新啓動異步任務，因爲The task can be executed only once

您可能希望這樣的事情ideal-way-to-cancel-an-executing-asynctask

doInBackground在UI線程不執行，那麼可以執行UI操作顯示的對話框

Answer 3

您可以通過使用publishProgress從內發送消息到UIThread實現這一目標並使用java的等待/通知 mechanisem等待untel用戶輸入他的輸入。

一個psudo代碼會是這個樣子：

public Object mLock = new Object(); 
protected void doInBackground(Params... params){ 
    /// do your requests. 
    publishProgress(Progress ...progress); 
    mLock.wait(); 

} 
protected void onProgressUpdate(Progress ....progress) { 
    // request user input here 
} 

，並從UIThread只是叫mLock.notify()問碼繼續。

您也可以通過拆分跨多個AsynchTasks你的邏輯執行slimier的行爲，因爲AsynchTasks通過共同的（靜態）的ThreadPoolExecutor管理和

Answer 4

You can create pause and resume method inside asyntask as below, and call it according to your convenience. 

     public class LoadFromCloudTask extends AsyncTask<Void, String, Boolean> { 

      public LoadFromCloudTask(LoadFromCloudTaskFragment loadFromCloudTaskFragment) { 
       this.loadFromCloudTaskFragment = loadFromCloudTaskFragment; 
      } 

    //call this when you want to halt the task   
        public void pause() { 
          if (this.getStatus().equals(Status.RUNNING)) { 
            try { 
              this.wait(); 
            } catch (InterruptedException e) { 
              e.printStackTrace(); 
            } 
          } 
        } 

    // call this when you need to resume the task 
        public void resume() { 
          if (this.getStatus().equals(Status.PENDING)) { 
            this.notify(); 
          } 
        } 

      @Override 
      protected Boolean doInBackground(Void... params) { 
       ... 
       ... 
       ... 
       // How possible I can halt my execution, prompt for user input, and continue execution based on user input. 
       // In Swing, I can ... 
       // 
       /* 
        // Hold the execution, and prompt for user input 
        final int result = JOptionPane.showConfirmDialog(LoadFromCloudJDialog.this, message, MessagesBundle.getString("question_title_overwrite_your_data_by_cloud_data_at"), JOptionPane.YES_NO_OPTION); 
        // Continue execution based on user input. 
       */ 
      } 
     }