的AsyncTask：使值到一個活動（onCreate方法）

Question

UPDATE1

活性：

public Integer _number = 0; 
@Override 
    public void onCreate(Bundle savedInstanceState) { 
if (_number >0) 
     { 
      Log.d("onSuccessfulExecute", ""+_number); 
     } 
     else 
     { 
      Log.d("onSuccessfulExecute", "nope empty songs lists"); 
     } 
} 

public int onSuccessfulExecute(int numberOfSongList) { 

_number = numberOfSongList; 

if (numberOfSongList >0) 
{ 
    Log.d("onSuccessfulExecute", ""+numberOfSongList); 
} 
else 
{ 
    Log.d("onSuccessfulExecute", "nope empty songs lists"); 
} 
    return numberOfSongList; 
} 

端UPDATE1

UPDATE：AsynchTask有它自己的外部類。

如何從的AsyncTask onPostExecute（）...傳遞一個價值活動

我的代碼並從onPostExecute返回值（）和更新用戶界面，但我正在尋找一種方式來設置活動變量（NumberOfSongList ）來自AsynchTask。

的AsyncTask類：

@Override 
    public void onPostExecute(asynctask.Payload payload) 
    { 
     AsyncTemplateActivity app = (AsyncTemplateActivity) payload.data[0]; 

      //the below code DOES UPDATE the UI textView control 
      int answer = ((Integer) payload.result).intValue(); 
      app.taskStatus.setText("Success: answer = "+answer); 

      //PROBLEM: 
      //i am trying to populate the value to an variable but does not seems like the way i am   doing: 
      app.NumberOfSongList = payload.answer; 
      .............. 
      .............. 
    } 

活動：

public Integer NumberOfSongList; 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     //Several UI Code 
     new ConnectingTask().execute(); 
     Log.d("onCreate", ""+NumberOfSongList); 

    } 

Answer 1

使用setter方法怎麼樣？例如

private int _number; 
public int setNumber(int number) { 
    _number = number; 
} 

UPDATE：

請看看這段代碼。這將做你想要完成的事情。

Activity類

public class TestActivity extends Activity { 
    public int Number; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 

     setContentView(R.layout.test); 

     Button btnDisplay = (Button) findViewById(R.id.btnDisplay); 
     btnDisplay.setOnClickListener(new OnClickListener() { 

      public void onClick(View v) { 
       Toast toast = Toast.makeText(v.getContext(), "Generated number: " + String.valueOf(Number), Toast.LENGTH_LONG); 
       toast.show();    
      } 
     }); 

     new TestTask(this).execute(); 
    } 
} 

的AsyncTask類

public class TestTask extends AsyncTask<Void, Void, Integer> { 
    private final Context _context; 
    private final String TAG = "TestTask"; 
    private final Random _rnd; 

    public TestTask(Context context){ 
     _context = context; 
     _rnd = new Random(); 
    } 

    @Override 
    protected void onPreExecute() { 
     //TODO: Do task init. 
     super.onPreExecute(); 
    } 

    @Override 
    protected Integer doInBackground(Void... params) { 
     //Simulate a long-running procedure. 
     try { 
      Thread.sleep(3000);   
     } catch (InterruptedException e) { 
      Log.e(TAG, e.getMessage()); 
     } 

     return _rnd.nextInt(); 
    } 

    @Override 
    protected void onPostExecute(Integer result) { 
     TestActivity test = (TestActivity) _context; 
     test.Number = result;  
     super.onPostExecute(result); 
    } 
} 

Answer 2

創建一個監聽。

建立一個新的類文件。稱它像MyAsyncListener，使它看起來像這樣：

public interface MyAsyncListener() { 
     onSuccessfulExecute(int numberOfSongList); 
} 

讓您的活動實施MyAsyncListener，即

public class myActivity extends Activity implements MyAsyncListener { 

監聽器添加到構造函數爲您的AsyncTask並將其設置爲一個全局變量在Async類中。然後在onPostExecute中調用監聽器的方法並傳遞數據。

public class MyCustomAsync extends AsyncTask<Void,Void,Void> { 

     MyAsyncListener mal; 

     public MyCustomAsync(MyAsyncListener listener) { 
      this.mal = listener; 
     } 

     @Override 
     public void onPostExecute(asynctask.Payload payload) { 
      \\update UI 
      mal.onSuccessfulExecute(int numberOfSongList); 
     } 
} 

現在，只要您的AsyncTask完成後，它會調用你的Activity類中的方法onSuccessfulExecute應該是這樣的：

@Override 
public void onSuccessfulExecute(int numberOfSongList) { 
     \\do whatever 
} 

好運。

Answer 3

謹慎的只是一個字：試圖在的AsyncTask舉行一個活動實例的引用時要非常小心 - 我發現這困難的方式:)。如果用戶在後臺任務仍在運行的情況下旋轉設備，則您的活動將被銷燬並重新創建，從而使對活動的引用無效。