ScheduledExecutorService作爲超時顯示沒有AlertDialog

Question

我試圖在我的應用程序中實現超時行爲。實際發生超時之前5秒鐘還應該有警告（alertdialog）。

我想使用ScheduledExecutorService來做到這一點。

這是迄今爲止我的相關代碼：

private final Context context = this; 

private ScheduledExecutorService sExService = Executors.newScheduledThreadPool(2); 

private RunnableScheduledFuture<?> sFutureTimeout; 
private RunnableScheduledFuture<?> sFutureDisconnect; 

private final Runnable timeoutRunnable = new Runnable(){ 
    @Override 
    public void run() {  
     showTimeoutAlertDialog(); 
    } 
}; 
private final Runnable disconnectRunnable = new Runnable(){ 
    @Override 
    public void run() { 
     disconnect(); 
    } 
}; 

和處理超時行爲的方法：

private void setTimeout(){ 
    sFutureTimeout = (RunnableScheduledFuture<?>) sExService.schedule(timeoutRunnable, 5, TimeUnit.SECONDS); 
} 

的setTimeout被調用的onCreate（），所以之後的應用程序應斷開5S發射。

private void showTimeoutAlertDialog(){ 

    new AlertDialog.Builder(context) 
      .setTitle("Disconnect in 5s") 
      .setCancelable(false) 
      .setPositiveButton("Abort", 
        new DialogInterface.OnClickListener() { 
         @Override 
         public void onClick(DialogInterface dialog, int id) { 
          sFutureDisconnect.cancel(false); 
          setTimeout(); 
         } 
        }).show(); 

    sFutureDisconnect = (RunnableScheduledFuture<?>) sExService.schedule(disconnectRunnable, 5, TimeUnit.SECONDS); 
} 

這裏是我所面臨的問題：

• 如果運行的稱爲「setTimeout的」設置爲「disconnectRunnable」，它工作正常，5秒後，應用程序斷開連接。

• 當我將它設置爲'timeoutRunnable'時，alertDialog未顯示+應用程序永遠不會斷開連接，即使'disconnectRunnable'應該在「showTimeoutAlertDialog」中調用5s之後！

我認爲ScheduledExecutorService在這裏出了問題，但我找不到解決方案。

謝謝您的幫助:)

Answer 1

您正在嘗試從UI線程顯示AlertDialog沒有那麼它不會有任何效果的方法showTimeoutAlertDialog()是從預定的線程池創建的工作線程調用。您可以使用Handler您的目的：

public class MyActivity extends Activity { 

    private final Context context = this; 

    private static Handler mHandler = new Handler(); 

    private final Runnable timeoutRunnable = new Runnable(){ 
     @Override 
     public void run() { 
      showTimeoutAlertDialog(); 
     } 
    }; 
    private final Runnable disconnectRunnable = new Runnable(){ 
     @Override 
     public void run() { 
      disconnect(); 
     } 
    }; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     setTimeout(); 
    } 

    private void disconnect() { 
     Log.e("MyActivity", "Disconnected"); 
    } 

    private void setTimeout(){ 
     mHandler.postDelayed(timeoutRunnable, 5000); 
    } 

    private void showTimeoutAlertDialog(){ 

     new AlertDialog.Builder(context) 
       .setTitle("Disconnect in 5s") 
       .setCancelable(false) 
       .setPositiveButton("Abort", 
         new DialogInterface.OnClickListener() { 
          @Override 
          public void onClick(DialogInterface dialog, int id) { 
           mHandler.removeCallbacks(disconnectRunnable); 
           setTimeout(); 
          } 
         }).show(); 

     mHandler.postDelayed(disconnectRunnable, 5000); 
    } 
}