在Android上的線程中運行無限循環時，應用程序崩潰。

Question

我有一個Android的服務如下：

public class TestService extends Service { 

    . 
    . 
    . // Variables 
    . 
    private Thread ChangeColors; 
    private final int[] colors = {Color.BLACK, Color.RED, Color.YELLOW, Color.BLUE, Color.GREEN}; 

    @Override 
    public void onStartCommand(Intent intent, int flags, int startID) { 

     LinearLayout layout = TestActivity.getLayout(); // Returns the layout from the activity class 
     changeColors = new Thread() { 

      int index = 0; 


      @Override 
      public void run() { 

        while(!isInterrupted()) { 

         try { 

          layout.setBackgroundColor(colors[index]); // Set the background to the Color at the index'th position in the array. 
          index ++; // Increment the index count. This will throw ArrayIndexOutOfBoundsException once the index > colors.length 
         } catch(ArrayIndexOutOfBoundsException exception) { 

          index = 0; // Then simply set the value of index back to 0 and continue looping. 
         } 
        } 
      } 
     }; 

     changeColors.start(); 
     return START_STICKY; 
    } 

    . 
    . 
    Other methods 
    . 
    . 

    @Override 
    public void onDestroy() { 

     super.onDestroy(); 
     changeColors.interrupt(); 
     Toast.makeText(this, "Stopped!", Toast.LENGTH_SHORT).show(); 
    } 
} 

該服務只是獲取android.widget.LinearLayout實例從Activity上的按鈕，點擊不斷變化的LinearLayout的背景色。

這是活動：

public class TestActivity extends Activity { 


    private static LinearLayout layout; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 

     layout = new LinearLayout(this); 
     layout.setOrientation(LinearLayout.VERTICAL); 
     layout.setLayoutParams(new LinearLayout.LayoutParams(

      LinearLayout.LayoutParams.FILL_PARENT, 
      LinearLayout.LayoutParams.FILL_PARENT 
     )); 

     Button butt = new Button(this); 
     butt.setText("Start thread!"); 
     button.setLayoutParams(new LinearLayout.LayoutParams(

      LinearLayout.LayoutParams.FILL_PARENT, 
      LinearLayout.LayoutParams.WRAP_CONTENT 
     )); 


     layout.addView(butt); 
     setContentView(layout); 


     butt.setOnClickListener(

      new View.OnClickListener() { 

       @Override 
       public void onClick(View view) { 

        butt.setBackgroundColor(Color.BLACK); 
        startService(getContextBase(), TestService.class); 
       } 
      } 
     ); 

     // I have another button coded here which on clicking calls the stopService() method. 
    } 



    public static LinearLayout getLayout() { 

     return layout; 
    } 
} 

程序似乎是相當簡單的。該應用在我的LG-L90手機上啓動得很好。但只要我點擊butt按鈕，butt的顏色就會變爲黑色，並且應用程序會立即崩潰，而不會在Service中運行循環。

我哪裏錯了？請幫忙。我真的想看看線程如何幫助我們做這些事情，並不斷改變可能有助於我在遊戲開發中的GUI。

在此先感謝。

Answer 1

您應該使用runOnUiThread進行UI操作。

public class MyService extends Service { 

    Handler handler; 

    public MyService() { 
    } 

    @Override 
    public void onCreate() { 
     super.onCreate(); 
     handler = new Handler(); 
    } 

    private void runOnUiThread(Runnable runnable) { 
     handler.post(runnable); 
    } 

    ... 
} 

，並確保您導入android.os.Handler，現在稱之爲runOnUiThread方法。