處理程序暫停或停止操作

Question

我有5 Buttons。每個Button的文本都設置爲list_of_letters的一個隨機字母。此外，這些字母每5秒鐘一次顯示一次 - 這就是爲什麼我使用Handler和Runnable。並且每隔5秒鐘，將添加到Button的那封信從list_of_letters中刪除。

問題：當所有5個Buttons包含一個字母時，Runnable仍在運行並每5秒從list_of_letters中刪除字母。有沒有辦法可以暫停Handler或停止其動作，以便只在Button不包含文字時纔會運行？

這裏是我的代碼：

for (int i = 0; i < 10; i++) { 
      Runnable x = new Runnable(){ 
       @Override 
       public void run(){ 
        random_counter = rand.nextInt(my_list_counter); 
        for(Button b:button_list) //contains the 5 buttons 
         if (b.getText().equals("")){ //if button is empty, add text to it 
          b.setText(list_of_letters.get(random_counter)); //sets text to random letter from List 
          break; 
         } 
        list_of_letters.remove(list_of_letters.get(random_counter)); //then removes that letter from the List 
        my_list_counter--; 
       } 
      }; 
      Handler handler = new Handler(); 
      handler.postAtTime(x, SystemClock.uptimeMillis() + i*5000); //a letter gets posted every 5 seconds 
     } 

編輯：這裏是我當前的代碼。在handler.post(x)有錯誤。該錯誤說：本地變量x可能尚未初始化。你的代碼的

final Runnable x = new Runnable() { 
      @Override 
       public void run(){ 
        if(my_list_counter <= 0) 
         return;  // i'm guessing my_list_counter is the length of the array/list. 
        random_counter = rand.nextInt(my_list_counter);   

        for(Button b:button_list) //contains the 5 buttons 
        { 
         if (b.getText().equals("")) { //if button is empty, add text to it 
          b.setText(list_of_letters.get(random_counter)); //sets text to random letter from List 
          list_of_letters.remove(list_of_letters.get(random_counter)); //then removes that letter from the List 
          my_list_counter--; 

          Handler handler = new Handler(); 
          handler.post(x); 
          // handler.postAtTime(x, SystemClock.uptimeMillis() + 5000); //a letter gets posted every 5 seconds 

          break; 
          } 
        } 
       } 
     }; 

Answer 1

移動一部分取出信件，並創建一個新的處理程序是在循環中：

@Override 
public void run(){ 
    if(my_list_counter <= 0) return;  // i'm guessing my_list_counter is the length of the array/list. 
    random_counter = rand.nextInt(my_list_counter);   

    for(Button b:button_list) //contains the 5 buttons 
    { 
     if (b.getText().equals("")) { //if button is empty, add text to it 
      b.setText(list_of_letters.get(random_counter)); //sets text to random letter from List 
      list_of_letters.remove(list_of_letters.get(random_counter)); //then removes that letter from the List 
      my_list_counter--; 

      Handler handler = new Handler(); 
      handler.postDelayed(x, 5000); //a letter gets posted every 5 seconds 

      break; 
      } 
    } 
} 

編輯：，你可以用它代替postAtTime postDelayed。間隔不會完全是5秒，但非常接近（毫秒差）。

將Runnable X = new Runnable()初始化移到任何方法之外。

例如，如果你的代碼是一個活動裏面：

public class yourClass extends Activity 
{ 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     //.... 
    } 

    Runnable x = new Runnable() 
    { 
     // the rest of the code. 
    }; 
} 

，並呼籲new Handler().post(x);得到它開始。