如何在选项卡之间切换时停止执行 AsyncTask，同时保留之前的内容

让我解释一下我的问题.. 假设我有三个选项卡 - 片段 ab1 / 片段 ab2 / 片段 ab3。

现在我在 FragmentTab1 中有列表视图。这里我使用AsyncTask加载数据OnCreateView().

数据正在完美加载。现在，当我查看详细信息并再次返回到 FragmentTab1 中的列表视图时。这里再次加载整个数据，浪费了之前加载的数据。

现在，我需要一个解决方案，它可以一次又一次地停止执行 AsyncTask，同时保留整个视图和数据，就像我们在已弃用的 TabHost 中执行工作一样。

任何帮助或建议将不胜感激。

这是我的代码。

public class Talk extends Fragment {
   /** Define global variables over here */
   //private ProgressDialog pDialog;
StaticApiList sal;
TalkModelAll tma;
JSONObject myJasonObject = null;
private ListView lv;
private ArrayList<TalkModelAll> m_ArrayList = null;
//ArrayList<String> stringArrayList = new ArrayList<String>();
TalkArrayAdapter taa;
Set<String> uniqueValues = new HashSet<String>();
TextView rowTextView = null;

int postid;
String title;
String thumsrc;
String largeimg;
String excert;
String description;
String cat;
String myUrl;
String jsonString;
int mCurCheckPosition;
String check_state = null;
String ccc;
LinearLayout myLinearLayout;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.talk, container, false);

    new TalkAsyncTask().execute();
    /*if(check_state == null){
    new TalkAsyncTask().execute();
    }else{
        new TalkAsyncTask().execute();
        Toast.makeText(getActivity(), "Have no null value for reloading fragment", Toast.LENGTH_LONG).show();
    }*/


    LinearLayout ll = (LinearLayout) rootView.findViewById(R.id.talk_ll);
    ll.setBackgroundColor(getActivity().getResources().getColor(R.color.talk_red_bottom));

    Log.d("track", "=================> " +uniqueValues.size());
    myLinearLayout = (LinearLayout) rootView.findViewById(R.id.talk_ll_uni);

    return rootView;
}

  private class TalkAsyncTask extends AsyncTask<String, Void, String> {

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

        /*pDialog = new ProgressDialog(getActivity());
        pDialog.setMessage("Please wait ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();*/
    }

    @Override
    protected String doInBackground(String... params) {
        sal = new StaticApiList();
        myUrl = StaticApiList.talk_api;
        HttpClient httpClient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(myUrl);

        try {
            HttpResponse httpResponse = httpClient.execute(httpGet);
            System.out.println("httpResponse");

            InputStream inputStream = httpResponse.getEntity().getContent();
            InputStreamReader inputStreamReader = new InputStreamReader(
                    inputStream);
            BufferedReader bufferedReader = new BufferedReader(
                    inputStreamReader);
            StringBuilder stringBuilder = new StringBuilder();
            String bufferedStrChunk = null;
            while ((bufferedStrChunk = bufferedReader.readLine()) != null) {
                stringBuilder.append(bufferedStrChunk);
            }
            jsonString = stringBuilder.toString();
            Log.i("talk_all_json", jsonString);
            return stringBuilder.toString();

        } catch (ClientProtocolException cpe) {
            System.out.println("Exception generates caz of httpResponse :"
                    + cpe);
            cpe.printStackTrace();
        } catch (IOException ioe) {
            System.out
                    .println("Second exception generates caz of httpResponse :"
                            + ioe);
            ioe.printStackTrace();
        }

        return null;
    }

    @SuppressLint("DefaultLocale")
    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        check_state = jsonString;
        try{
            m_ArrayList = new ArrayList<TalkModelAll>(); 
            if (jsonString.length() > 0) {
                   JSONArray jArray = new JSONArray(jsonString);

                        for(int i=0; i < jArray.length(); i++) {

                            JSONObject jObject = jArray.getJSONObject(i);

                            title = jObject.getString("title");
                            thumsrc = jObject.getString("thumsrc");
                            largeimg = jObject.getString("largeimg");
                            excert = jObject.getString("excert");
                            description = jObject.getString("description");
                            cat = jObject.getString("cat");
                            postid = jObject.getInt("postid");
                            /////////// stringArrayList.add(jObject.getString("cat"));


                            uniqueValues.add(jObject.getString("cat"));   // Set unique elements in string array list
                             int a = 0;
                                if(a == 0){
                                    uniqueValues.add("All,");
                                     a = 1;
                                }
                            ccc = uniqueValues.toString();
                            Log.d("unique","========================> " + ccc);

                            Log.d("talklog", "Title -> " + title + " , thumsrc -> " + thumsrc + " , largeimg -> " + largeimg 
                                    + " , excert -> " + excert + " , description -> " + description + " , cat -> " + cat + " , " + "PostId " + postid );
                            Log.d("talklog", "============================= end of " + i + " ===============================");

                            tma = new TalkModelAll();
                            tma.title = title;
                            tma.thumsrc = thumsrc;
                            tma.largeimg = largeimg;
                            tma.excert = excert;
                            tma.description = description;
                            tma.cat = cat;
                            tma.postid = postid;

                            m_ArrayList.add(tma);

                        } 

                        String[] split_unique = ccc.split(",");

                        Arrays.sort(split_unique);

                        for(int i = 0; i < split_unique.length; i++){
                            Log.d("split_unique", "====>><< " + split_unique.length);
                            Log.d("split_unique", "====>><< " + ccc.split(",")[i]);
                        }

                      //  When we need dynamic number of text view's ..
                     final int N = split_unique.length; // total number of textviews to add

                    final TextView[] myTextViews = new TextView[N]; // create an empty array;

                    for (int i = 0; i < N; i++) {
                       // create a new textview
                       rowTextView = new TextView(getActivity());

                       // set some properties of rowTextView or something talk_ll_uni
                       rowTextView.setText((split_unique[i].replaceAll("[|?*<\":>+\\[\\]/']", "") + "   ").toUpperCase());
                       rowTextView.setTextColor(getActivity().getResources().getColor(R.color.talk_red_bottom));
                       rowTextView.setTextSize(25);
                       rowTextView.setId(i);
                       // add the textview to the linearlayout
                       myLinearLayout.addView(rowTextView);



                       // saving a reference to the textview for later
                       myTextViews[i] = rowTextView;
                   }


                      //if you want your array
                     /////  String [] stringArray = stringArrayList.toArray(new String[stringArrayList.size()]);


            }

            taa = new TalkArrayAdapter(getActivity(), m_ArrayList);
            lv = (ListView) getActivity().findViewById(R.id.talk_list);
            lv.setVisibility(View.VISIBLE); 
            lv.setAdapter(taa);

            lv.setOnItemClickListener(new OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView<?> arg0, View arg1,
                        int arg2, long arg3) {
                    // TODO Auto-generated method stub

                    TalkDetail fragment = new TalkDetail();
                    Bundle bundle = new Bundle();

                    bundle.putString("title", m_ArrayList.get(arg2).title);
                    bundle.putString("largeimg", m_ArrayList.get(arg2).largeimg);
                    bundle.putString("excert", m_ArrayList.get(arg2).excert);
                    bundle.putString("description", m_ArrayList.get(arg2).description);
                    bundle.putString("cat", m_ArrayList.get(arg2).cat);
                    //bundle.putInt("postid", m_ArrayList.get(arg2).postid);

                    fragment.setArguments(bundle);
                    ((BaseContainerFragment)getParentFragment()).replaceFragment(fragment, true);

                }
            });

        }catch(Exception e){
            e.printStackTrace();
        }

        //pDialog.dismiss();

    }

}

}

我用谷歌搜索了很多，但无法得到确切的观点。我还在 StackOverFlow 上使用其他建议的内容时检查了不同的方法。

预先感谢您的合作。

为此..首先每当你回到fragment你必须再次检查是否Asynchtask是否已经执行..这意味着检查加载的数据..如果数据为空，则您已加载数据，否则您无需调用Asynchtask再次..

在您的片段中维护一个布尔标志..在 onPostExecute 将其设置为 true..每当您将一个选项卡移动到另一个片段时，将被删除并再次添加，因此在您的 onCreateView 方法中，如果布尔标志为 false 则执行异步任务..ohterwise 数据已经是已加载..

或维持一个singleton类并再次设置加载的数据，返回活动从单例类获取数据，如果数据为空，则加载加载它并设置为单例类。

In your onDestroy()的方法fragment停止AsynchTask像这样..

@Override
public void onDestroy() {
    super.onDestroy();
    if (applicationLoadTask != null) {
        if (!applicationLoadTask.isCancelled()) {
            applicationLoadTask.cancel(true);
        }
    }
}