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AsyncTask检测是否完成(AsyncTask detecting if done)

 我创建了一个AsyncTask，当我执行它时从网站加载数据。 目前，我得到一个空指针异常，我认为是因为我想太早填充UI，所以我希望创建一些if语句，说如果AsyncTask没有完成显示加载图形和填充数据的时间。 但我不确定如何去做这件事，是否有人知道我该如何实现这一目标，或者至少让我朝正确的方向发展。 
 

 这是我的代码到目前为止 
 

public void checkPreferences(){

    SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
    ChosenMethod = preferences.getString("ChosenMethod", ChosenMethod);
    ChosenLeagueID = preferences.getString("ChosenLeagueId", ChosenLeagueID);
    ChosenTeamId = preferences.getString("ChosenTeamId", ChosenTeamId);

    Log.v("lc", "newsurl" + newsFeedURL);


    Log.v("myapp", "ChosenMethod Home = " + ChosenMethod);
    Log.v("myapp", "ChosenLeagueID Home = " + ChosenLeagueID);
    Log.v("myapp", "ChosenTeamID Home = " + ChosenTeamId);

    if (ChosenMethod.equals("Team")) {
        setContentView(R.layout.homeactteam2);
        newsAmount = 5;

    } else {
        newsAmount = 10;
        setContentView(R.layout.homeactteam);
    }

}


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

    //Check Preferences which sets UI

    checkPreferences();
   PostTask posttask;
   posttask = new PostTask();
   posttask.execute();

   FillData();


    Button backbtn = (Button) findViewById(R.id.backbtn);

    //Listening to button event
    backbtn.setOnClickListener(new View.OnClickListener() {

        public void onClick(View arg0) {
            //Starting a new Intent
            Intent previousScreen = new Intent(getApplicationContext(), ChooseTeamActivity.class);
            ChosenMethod = "null";
            SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = preferences.edit();
            editor.putString("ChosenMethod", ChosenMethod);            
            editor.commit();
            previousScreen.putExtra("FullData", fulldata);
            startActivity(previousScreen);


        }
    });

//((PullToRefreshListView) getListView()).setOnRefreshListener(new OnRefreshListener() {
//   
//    public void onRefresh() {
//        // Do work to refresh the list here.
//        loadData();
//    }
//});
//


}



public void loadNewsFeed(){

     newsFeedRequest = "website/" + chosenLeagueId + "/news?timestamp=" + unixTimeStamp;
     newsFeedURL = "https://www.website.com" + newsFeedRequest; 

        String myhash = buildHmacSignature(apiKey, newsFeedURL);
        HttpClient client = new DefaultHttpClient();
        HttpPost post = new HttpPost(newsFeedURL);

        List<NameValuePair> pairs = new ArrayList<NameValuePair>();
        pairs.add(new BasicNameValuePair("requestToken", myhash));
        pairs.add(new BasicNameValuePair("apiUser", apiUser));

            try {
                post.setEntity (new UrlEncodedFormEntity(pairs));
                HttpResponse response = client.execute(post);
                BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
                String json = reader.readLine();
                fulldata = String.valueOf(json);
                Log.v("myApp","newsdata" + fulldata);

                newsList = new ArrayList<String>();
                newsList2 = new ArrayList<String>();
                newsList3 = new ArrayList<String>();
                imageList = new ArrayList<String>();


                JSONObject obj = new JSONObject(json);    
                JSONObject objData = obj.getJSONObject("data");
                JSONArray jArray = objData.getJSONArray("news");
                Log.v("lc","newsAmount= " + newsAmount);

                   for(int t = 0; t < newsAmount; t++){
                       JSONObject newsTitleDict = jArray.getJSONObject(t);
                       imageList.add(newsTitleDict.getString("image_small"));
                     newsList3.add(newsTitleDict.getString("title"));

                   }

                   for(int t = 0; t < 1; t++){
                       JSONObject newsTitleDict = jArray.getJSONObject(t);

                 newsList.add(newsTitleDict.getString("title"));
            //       newsList2.add(newsTitleDict.getString("title"));

                   }



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


}           


public void loadResultsFeed(){


    resultsFeedRequest = "website/" + chosenLeagueId + "/results?&team_id=" + ChosenTeamId + "&limit=31&timestamp=" + unixTimeStamp;
    resultsFeedURL = "https://www.website.com" + resultsFeedRequest;    

    String myhash = buildHmacSignature(apiKey, resultsFeedURL);

    HttpClient client = new DefaultHttpClient();
    HttpPost post = new HttpPost(resultsFeedURL);

    List<NameValuePair> pairs = new ArrayList<NameValuePair>();
    pairs.add(new BasicNameValuePair("requestToken", myhash));
    pairs.add(new BasicNameValuePair("apiUser", apiUser));

    try {
        post.setEntity (new UrlEncodedFormEntity(pairs));
        HttpResponse response = client.execute(post);
        BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
        String json = reader.readLine();
        fulldata = String.valueOf(json);
        Log.v("myApp","resultsdata" + fulldata);

        newsList = new ArrayList<String>();
        newsList2 = new ArrayList<String>();
        newsList3 = new ArrayList<String>();
        imageList = new ArrayList<String>();


        JSONObject obj = new JSONObject(json);    
        JSONObject objData = obj.getJSONObject("data");
        JSONArray jArray = objData.getJSONArray("results");


        if(jArray.length() < 1) loadLastResults();



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


}


public void loadLastResults(){

    resultsFeedRequest = "website/" + chosenLeagueId + "/results?month=04&team_id=" + ChosenTeamId + "&limit=31&timestamp=" + unixTimeStamp;
    resultsFeedURL = "https://www.website.com" + resultsFeedRequest;    

     String myhash = buildHmacSignature(apiKey, resultsFeedURL);

    Date anotherCurDate = new Date();  
    SimpleDateFormat formatter = new SimpleDateFormat("MM");  
    String CurMonth = formatter.format(anotherCurDate);  

    int Int = Integer.parseInt(CurMonth);

    int MonthInt = Int -1;


    CurMonth = (String) (String.valueOf(MonthInt));



    if (CurMonth.equals("1")){

        lastMonth = "12";

    }    
     else {
        if(CurMonth.length() < 2){
            lastMonth = "0" + CurMonth;
        } else {
            lastMonth = CurMonth;
        }
    }

    Log.v("lc","month= " + CurMonth);
    Log.v("lc","LastMonth= " + lastMonth);


        HttpClient client = new DefaultHttpClient();
        HttpPost post = new HttpPost(resultsFeedURL);

        List<NameValuePair> pairs = new ArrayList<NameValuePair>();
        pairs.add(new BasicNameValuePair("requestToken", myhash));
        pairs.add(new BasicNameValuePair("apiUser", apiUser));

        try {
            post.setEntity (new UrlEncodedFormEntity(pairs));
            HttpResponse response = client.execute(post);
            BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
            String json = reader.readLine();
            fulldata = String.valueOf(json);
            Log.v("myApp","resultsdata" + fulldata);

            newsList = new ArrayList<String>();
            newsList2 = new ArrayList<String>();
            newsList3 = new ArrayList<String>();
            imageList = new ArrayList&t;String>();


            JSONObject obj = new JSONObject(json);    
            JSONObject objData = obj.getJSONObject("data");
            JSONArray jArray = objData.getJSONArray("results");


               for(int t = 0; t < 1; t++){

                   resultsDict = jArray.getJSONObject(t);
                  HomeTeam = resultsDict.getString("hometeam");
                  AwayTeam = resultsDict.getString("awayteam");
                  HomeScore = resultsDict.getString("homescore");
                  AwayScore = resultsDict.getString("awayscore");
                  Attendance = resultsDict.getString("attendance");
                  Division = resultsDict.getString("division");

                  Log.v("lc","hometeam" + HomeTeam);
                  Log.v("lc","awayteam" + AwayTeam);


               }


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


    }   


public class PostTask extends AsyncTask<Void, String, Boolean> {

    @Override
    protected Boolean doInBackground(Void... params) {
        boolean result = false;
        loadNewsFeed();
        loadResultsFeed();
        loadLastResults();
        publishProgress("progress");
        return result;
    }

    protected void onProgressUpdate(String... progress) {
        StringBuilder str = new StringBuilder();
            for (int i = 1; i < progress.length; i++) {
                str.append(progress[i] + " ");
            }
    }

}

public void FillData(){ 


     if (ChosenMethod.equals("Team")) {


         resultsView = LayoutInflater.from(getBaseContext()).inflate(R.layout.resultscell,
                 null);

       TextView homeTeam = (TextView) resultsView.findViewById(R.id.HomeTeam);
       homeTeam.setText(HomeTeam);

       TextView awayTeam = (TextView) resultsView.findViewById(R.id.AwayTeam);
       awayTeam.setText(AwayTeam);

       TextView homeScore = (TextView) resultsView.findViewById(R.id.HomeScore);
       homeScore.setText(HomeScore);

       TextView awayScore = (TextView) resultsView.findViewById(R.id.AwayScore);
       awayScore.setText(AwayScore);

       TextView attendance = (TextView) resultsView.findViewById(R.id.Attendence);
       attendance.setText("Att:" + Attendance);

       TextView division = (TextView) resultsView.findViewById(R.id.Division);
       division.setText(Division);

        arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);

         String[] mStrings = (String[]) imageList.toArray(new String[imageList.size()]);
         String[] news = (String[]) newsList3.toArray(new String[newsList3.size()]);

         arrayAdapter3 = new LazyAdapter(this, mStrings, news);


            ListView list = getListView();
               list.setTextFilterEnabled(true);

               LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
                View header = inflater.inflate( R.layout.homeheader, list, false);
                View header2 = inflater.inflate( R.layout.homeheader2, list, false);
                View header3 = inflater.inflate( R.layout.homeheader3, list, false);


        //setListAdapter (arrayAdapter);


            adapter = new MergeAdapter();
            adapter.addView(header);
            adapter.addAdapter(arrayAdapter);
            adapter.addView(header2);
            adapter.addView(resultsView);
            adapter.addView(header3);
            adapter.addAdapter(arrayAdapter3);
            setListAdapter(adapter);



     } else {

         arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);
            arrayAdapter2 = new ArrayAdapter<String>(this, R.layout.single_item, newsList2);
            //arrayAdapter3 = new ArrayAdapter(this, R.layout.complex_item, newsList3);

             String[] mStrings = (String[]) imageList.toArray(new String[imageList.size()]);
             String[] news = (String[]) newsList3.toArray(new String[newsList3.size()]);


             arrayAdapter3 = new LazyAdapter(this, mStrings, news);


                ListView list = getListView();
                   list.setTextFilterEnabled(true);

                   LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
                    View header3 = inflater.inflate( R.layout.homeheader3, list, false);


            //setListAdapter (arrayAdapter);


                adapter = new MergeAdapter();
                adapter.addView(header3);
                adapter.addAdapter(arrayAdapter3);
                setListAdapter(adapter);
         } 
}


I have created an AsyncTask that loads data from a website then when I execute it. At the moment I'm getting a null pointer exception which I think is caused because I'm trying to fill the UI too early so I'm hoping to create some kind of if statement that says if AsyncTask isn't complete show a loading graphic and when it is fill the data. But I'm not sure how to go about doing this does anyone know how I could achieve this or at least point me in the right direction.
 

Here's my code so far
 

public void checkPreferences(){

    SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
    ChosenMethod = preferences.getString("ChosenMethod", ChosenMethod);
    ChosenLeagueID = preferences.getString("ChosenLeagueId", ChosenLeagueID);
    ChosenTeamId = preferences.getString("ChosenTeamId", ChosenTeamId);

    Log.v("lc", "newsurl" + newsFeedURL);


    Log.v("myapp", "ChosenMethod Home = " + ChosenMethod);
    Log.v("myapp", "ChosenLeagueID Home = " + ChosenLeagueID);
    Log.v("myapp", "ChosenTeamID Home = " + ChosenTeamId);

    if (ChosenMethod.equals("Team")) {
        setContentView(R.layout.homeactteam2);
        newsAmount = 5;

    } else {
        newsAmount = 10;
        setContentView(R.layout.homeactteam);
    }

}


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

    //Check Preferences which sets UI

    checkPreferences();
   PostTask posttask;
   posttask = new PostTask();
   posttask.execute();

   FillData();


    Button backbtn = (Button) findViewById(R.id.backbtn);

    //Listening to button event
    backbtn.setOnClickListener(new View.OnClickListener() {

        public void onClick(View arg0) {
            //Starting a new Intent
            Intent previousScreen = new Intent(getApplicationContext(), ChooseTeamActivity.class);
            ChosenMethod = "null";
            SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = preferences.edit();
            editor.putString("ChosenMethod", ChosenMethod);            
            editor.commit();
            previousScreen.putExtra("FullData", fulldata);
            startActivity(previousScreen);


        }
    });

//((PullToRefreshListView) getListView()).setOnRefreshListener(new OnRefreshListener() {
//   
//    public void onRefresh() {
//        // Do work to refresh the list here.
//        loadData();
//    }
//});
//


}



public void loadNewsFeed(){

     newsFeedRequest = "website/" + chosenLeagueId + "/news?timestamp=" + unixTimeStamp;
     newsFeedURL = "https://www.website.com" + newsFeedRequest; 

        String myhash = buildHmacSignature(apiKey, newsFeedURL);
        HttpClient client = new DefaultHttpClient();
        HttpPost post = new HttpPost(newsFeedURL);

        List<NameValuePair> pairs = new ArrayList<NameValuePair>();
        pairs.add(new BasicNameValuePair("requestToken", myhash));
        pairs.add(new BasicNameValuePair("apiUser", apiUser));

            try {
                post.setEntity (new UrlEncodedFormEntity(pairs));
                HttpResponse response = client.execute(post);
                BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
                String json = reader.readLine();
                fulldata = String.valueOf(json);
                Log.v("myApp","newsdata" + fulldata);

                newsList = new ArrayList<String>();
                newsList2 = new ArrayList<String>();
                newsList3 = new ArrayList<String>();
                imageList = new ArrayList<String>();


                JSONObject obj = new JSONObject(json);    
                JSONObject objData = obj.getJSONObject("data");
                JSONArray jArray = objData.getJSONArray("news");
                Log.v("lc","newsAmount= " + newsAmount);

                   for(int t = 0; t < newsAmount; t++){
                       JSONObject newsTitleDict = jArray.getJSONObject(t);
                       imageList.add(newsTitleDict.getString("image_small"));
                     newsList3.add(newsTitleDict.getString("title"));

                   }

                   for(int t = 0; t < 1; t++){
                       JSONObject newsTitleDict = jArray.getJSONObject(t);

                 newsList.add(newsTitleDict.getString("title"));
            //       newsList2.add(newsTitleDict.getString("title"));

                   }



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


}           


public void loadResultsFeed(){


    resultsFeedRequest = "website/" + chosenLeagueId + "/results?&team_id=" + ChosenTeamId + "&limit=31&timestamp=" + unixTimeStamp;
    resultsFeedURL = "https://www.website.com" + resultsFeedRequest;    

    String myhash = buildHmacSignature(apiKey, resultsFeedURL);

    HttpClient client = new DefaultHttpClient();
    HttpPost post = new HttpPost(resultsFeedURL);

    List<NameValuePair> pairs = new ArrayList<NameValuePair>();
    pairs.add(new BasicNameValuePair("requestToken", myhash));
    pairs.add(new BasicNameValuePair("apiUser", apiUser));

    try {
        post.setEntity (new UrlEncodedFormEntity(pairs));
        HttpResponse response = client.execute(post);
        BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
        String json = reader.readLine();
        fulldata = String.valueOf(json);
        Log.v("myApp","resultsdata" + fulldata);

        newsList = new ArrayList<String>();
        newsList2 = new ArrayList<String>();
        newsList3 = new ArrayList<String>();
        imageList = new ArrayList<String>();


        JSONObject obj = new JSONObject(json);    
        JSONObject objData = obj.getJSONObject("data");
        JSONArray jArray = objData.getJSONArray("results");


        if(jArray.length() < 1) loadLastResults();



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


}


public void loadLastResults(){

    resultsFeedRequest = "website/" + chosenLeagueId + "/results?month=04&team_id=" + ChosenTeamId + "&limit=31&timestamp=" + unixTimeStamp;
    resultsFeedURL = "https://www.website.com" + resultsFeedRequest;    

     String myhash = buildHmacSignature(apiKey, resultsFeedURL);

    Date anotherCurDate = new Date();  
    SimpleDateFormat formatter = new SimpleDateFormat("MM");  
    String CurMonth = formatter.format(anotherCurDate);  

    int Int = Integer.parseInt(CurMonth);

    int MonthInt = Int -1;


    CurMonth = (String) (String.valueOf(MonthInt));



    if (CurMonth.equals("1")){

        lastMonth = "12";

    }    
     else {
        if(CurMonth.length() < 2){
            lastMonth = "0" + CurMonth;
        } else {
            lastMonth = CurMonth;
        }
    }

    Log.v("lc","month= " + CurMonth);
    Log.v("lc","LastMonth= " + lastMonth);


        HttpClient client = new DefaultHttpClient();
        HttpPost post = new HttpPost(resultsFeedURL);

        List<NameValuePair> pairs = new ArrayList<NameValuePair>();
        pairs.add(new BasicNameValuePair("requestToken", myhash));
        pairs.add(new BasicNameValuePair("apiUser", apiUser));

        try {
            post.setEntity (new UrlEncodedFormEntity(pairs));
            HttpResponse response = client.execute(post);
            BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
            String json = reader.readLine();
            fulldata = String.valueOf(json);
            Log.v("myApp","resultsdata" + fulldata);

            newsList = new ArrayList<String>();
            newsList2 = new ArrayList<String>();
            newsList3 = new ArrayList<String>();
            imageList = new ArrayList<String>();


            JSONObject obj = new JSONObject(json);    
            JSONObject objData = obj.getJSONObject("data");
            JSONArray jArray = objData.getJSONArray("results");


               for(int t = 0; t < 1; t++){

                   resultsDict = jArray.getJSONObject(t);
                  HomeTeam = resultsDict.getString("hometeam");
                  AwayTeam = resultsDict.getString("awayteam");
                  HomeScore = resultsDict.getString("homescore");
                  AwayScore = resultsDict.getString("awayscore");
                  Attendance = resultsDict.getString("attendance");
                  Division = resultsDict.getString("division");

                  Log.v("lc","hometeam" + HomeTeam);
                  Log.v("lc","awayteam" + AwayTeam);


               }


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


    }   


public class PostTask extends AsyncTask<Void, String, Boolean> {

    @Override
    protected Boolean doInBackground(Void... params) {
        boolean result = false;
        loadNewsFeed();
        loadResultsFeed();
        loadLastResults();
        publishProgress("progress");
        return result;
    }

    protected void onProgressUpdate(String... progress) {
        StringBuilder str = new StringBuilder();
            for (int i = 1; i < progress.length; i++) {
                str.append(progress[i] + " ");
            }
    }

}

public void FillData(){ 


     if (ChosenMethod.equals("Team")) {


         resultsView = LayoutInflater.from(getBaseContext()).inflate(R.layout.resultscell,
                 null);

       TextView homeTeam = (TextView) resultsView.findViewById(R.id.HomeTeam);
       homeTeam.setText(HomeTeam);

       TextView awayTeam = (TextView) resultsView.findViewById(R.id.AwayTeam);
       awayTeam.setText(AwayTeam);

       TextView homeScore = (TextView) resultsView.findViewById(R.id.HomeScore);
       homeScore.setText(HomeScore);

       TextView awayScore = (TextView) resultsView.findViewById(R.id.AwayScore);
       awayScore.setText(AwayScore);

       TextView attendance = (TextView) resultsView.findViewById(R.id.Attendence);
       attendance.setText("Att:" + Attendance);

       TextView division = (TextView) resultsView.findViewById(R.id.Division);
       division.setText(Division);

        arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);

         String[] mStrings = (String[]) imageList.toArray(new String[imageList.size()]);
         String[] news = (String[]) newsList3.toArray(new String[newsList3.size()]);

         arrayAdapter3 = new LazyAdapter(this, mStrings, news);


            ListView list = getListView();
               list.setTextFilterEnabled(true);

               LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
                View header = inflater.inflate( R.layout.homeheader, list, false);
                View header2 = inflater.inflate( R.layout.homeheader2, list, false);
                View header3 = inflater.inflate( R.layout.homeheader3, list, false);


        //setListAdapter (arrayAdapter);


            adapter = new MergeAdapter();
            adapter.addView(header);
            adapter.addAdapter(arrayAdapter);
            adapter.addView(header2);
            adapter.addView(resultsView);
            adapter.addView(header3);
            adapter.addAdapter(arrayAdapter3);
            setListAdapter(adapter);



     } else {

         arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);
            arrayAdapter2 = new ArrayAdapter<String>(this, R.layout.single_item, newsList2);
            //arrayAdapter3 = new ArrayAdapter(this, R.layout.complex_item, newsList3);

             String[] mStrings = (String[]) imageList.toArray(new String[imageList.size()]);
             String[] news = (String[]) newsList3.toArray(new String[newsList3.size()]);


             arrayAdapter3 = new LazyAdapter(this, mStrings, news);


                ListView list = getListView();
                   list.setTextFilterEnabled(true);

                   LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
                    View header3 = inflater.inflate( R.layout.homeheader3, list, false);


            //setListAdapter (arrayAdapter);


                adapter = new MergeAdapter();
                adapter.addView(header3);
                adapter.addAdapter(arrayAdapter3);
                setListAdapter(adapter);
         } 
}


原文：https://stackoverflow.com/questions/10946499
更新时间：2021-12-23 11:12

最满意答案

 好的，我自己找到了解决方案。 这里的问题是关于竞争条件 - 一个事件试图停止计数（这意味着引发另一个事件）然后再次启动它（这是有问题的，因为我的功能（我猜）已经混乱了第一个，可能是第二个事件甚至没有添加到事件检测队列中）。 如果我的解释错了，我会感激一些批评;） 
 

 这是两个修改过的函数，它们正确地解决了线程管理。 关键是让其他事件完成他们的工作，直到我得到理想的状态。 
 

 当我想关闭计数时，我让应用程序从队列中执行事件，直到两个线程都不忙（'while'循环）： 
 

private: void turnOffAcquisition() {

    if (counting_paused)
        return;

    if (plot_bgworker->IsBusy)
        plot_bgworker->CancelAsync();
    if (data_bgworker->IsBusy)
        data_bgworker->CancelAsync();

    while((plot_bgworker->IsBusy) || (data_bgworker->IsBusy))   // Continue to process events until both workers stop working
        Application::DoEvents();                                // Then, you can process another thread requests! :)

    label_timer->Enabled = false;
    counting_paused = true;
 }

 

 类似地，当我想重新开始计数时，我让应用程序执行事件，直到我检查两个线程都忙（再次，'while'循环）： 
 

private: void turnOnAcquisition() {
    if (!counting_paused)
        return;

    if (!plot_bgworker->IsBusy)
        plot_bgworker->RunWorkerAsync();
    if (!data_bgworker->IsBusy)
        data_bgworker->RunWorkerAsync();

    while((!plot_bgworker->IsBusy) || (!data_bgworker->IsBusy)) // Continue to process events until both workers start working
        Application::DoEvents();                                // Then, you can process another thread requests! :)

    label_timer->Enabled = true;
    counting_paused = false;
}


Ok, I found the solution by myself. The problem here was about the race condition - one event tried to stop counting (which meant raising another event) and then starting it again (which was problematic, as my function (I guess) was already cluttered with the first one and probably the second event wasn't even added to the event detected queue). If I am wrong with the explanation, I would appreciate some criticism down there ;)
 

Here are two modified functions, which solved thread management correctly. The key was to let the other events do their work until I get desired state.
 

When I want to turn off counting, I let the applications do the events from the queue until both threads will not be busy (the 'while' loop):
 

private: void turnOffAcquisition() {

    if (counting_paused)
        return;

    if (plot_bgworker->IsBusy)
        plot_bgworker->CancelAsync();
    if (data_bgworker->IsBusy)
        data_bgworker->CancelAsync();

    while((plot_bgworker->IsBusy) || (data_bgworker->IsBusy))   // Continue to process events until both workers stop working
        Application::DoEvents();                                // Then, you can process another thread requests! :)

    label_timer->Enabled = false;
    counting_paused = true;
 }

 

Similarily, when I want to restart counting, I let the application do the events until I check that both threads are busy (again, the 'while' loop):
 

private: void turnOnAcquisition() {
    if (!counting_paused)
        return;

    if (!plot_bgworker->IsBusy)
        plot_bgworker->RunWorkerAsync();
    if (!data_bgworker->IsBusy)
        data_bgworker->RunWorkerAsync();

    while((!plot_bgworker->IsBusy) || (!data_bgworker->IsBusy)) // Continue to process events until both workers start working
        Application::DoEvents();                                // Then, you can process another thread requests! :)

    label_timer->Enabled = true;
    counting_paused = false;
}

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