後退按鈕只關閉進度對話框而不是AsyncTask

Question

我試圖在用戶點擊後退按鈕時取消我的aynctask。我已經完成了關於使用哪種方法進行此項操作的研究，並且發現很難弄清楚爲什麼有多種方法。我找到了一種方法並嘗試了它，但它僅解散了我的ProgressDialog，而我的aynctassk仍然執行。那麼有人可以幫助我解決這個問題，讓我的asynctask忽略正確的方法。

@Override 
public void onBackPressed() 
{    
    /** If user Pressed BackButton While Running Asynctask 
     this will close the ASynctask. 
    */ 
    if (mTask != null && mTask.getStatus() != AsyncTask.Status.FINISHED) 
    { 
     mTask.cancel(true); 
    }   
    super.onBackPressed(); 
    finish(); 
} 


@Override 
protected void onDestroy() { 
    // TODO Auto-generated method stub 


/** If Activity is Destroyed While Running Asynctask 
     this will close the ASynctask. */ 

if (mTask != null && mTask.getStatus() != AsyncTask.Status.FINISHED) 
{ 
    mTask.cancel(true); 
    } 

    super.onDestroy(); 

} 

@Override 
protected void onPause() { 
    // TODO Auto-generated method stub 


if (pDialog != null) 
{ 
    if(pDialog.isShowing()) 
    { 
     pDialog.dismiss(); 
    } 
     super.onPause(); 

    } 

} 

並請讓我知道如果我需要後我doInBackGround方法的問題

protected String doInBackground(String... args) { 

    try { 
     Intent in = getIntent(); 
     String searchTerm = in.getStringExtra("TAG_SEARCH"); 
     String query = URLEncoder.encode(searchTerm, "utf-8"); 
     String URL = "http://example.com"; 
     JSONParsser jParser = new JSONParsser(); 
     JSONObject json = jParser.readJSONFeed(URL); 
     try { 

      JSONArray questions = json.getJSONObject("all").getJSONArray("questions"); 

      for(int i = 0; i < questions.length(); i++) { 
       JSONObject question = questions.getJSONObject(i); 


      String Subject = question.getString(TAG_QUESTION_SUBJECT); 
      String ChosenAnswer = question.getString(TAG_QUESTION_CHOSENANSWER); 
      String Content = question.getString(TAG_QUESTION_CONTENT); 



         HashMap<String, String> map = new HashMap<String, String>(); 

         map.put(TAG_QUESTION_SUBJECT, Subject); 
         map.put(TAG_QUESTION_CONTENT, Content); 
         map.put(TAG_QUESTION_CHOSENANSWER, ChosenAnswer); 

         questionList.add(map); 

      } 


      } catch (JSONException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
    } catch (UnsupportedEncodingException e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } 

        return null; 

} 

Answer 1

我認爲這個問題是在你的AsyncTask的doInBackground方法。當你用mTask.cancel(true);取消你的AsyncTask時，它不會取消任務，它只是設置一個標誌。如果任務已被取消（標記爲取消），則需要檢查DoInBackground方法，如果有，則返回。

例子：

protected Long doInBackground(URL... urls) { 
     int count = urls.length; 
     long totalSize = 0; 
     for (int i = 0; i < count; i++) { 
      totalSize += Downloader.downloadFile(urls[i]); 
      publishProgress((int) ((i/(float) count) * 100)); 
      // Escape early if cancel() is called 
      if (isCancelled()) break; 
     } 
     return totalSize; 
    } 

來源：http://developer.android.com/reference/android/os/AsyncTask.html