在 AsyncTask 的 onPostExecute 方法中获取的返回值

Question

所以我从另一个activity 拨打checkbetoutcome()。我的目标是执行 AsyncTask 并返回在 onPostExecute() 方法中填充的 finaloutcomes 变量。我如何实现这一点，以便我不会得到一个空的finaloutcomes 变量，因为AsyncTask 在后台运行并且返回finaloutcomes，代码在onPostExecute 方法完成之前执行？

public HashMap<String,String> checkbetoutcome() {
    new LoadAllGamet().execute();
    return finaloutcomes;
}

**Check_Bet.java

public class CheckBet {
    private String bet;
    private ArrayList<Map<String,String>> allbetsmap = new ArrayList<>();
    private ArrayList<String> userstatuses = new ArrayList<>();
    private String status = "open";
    private static String url_check_bet = "****";
    String resulttest;
    private ArrayList<Map<String,String>> passtocheck = new ArrayList<>();
    private String currentitem;
    private String game;
    private onResultListener lister = new onResultListener() {
        @Override
        public void showResult(HashMap<String, String> finaloutcomes) {

        }
    };
    private String c = "";
    JSONArray allgames = null;
    private HashMap<String,String> finaloutcomes = new HashMap<String,String>();


    public CheckBet(String bet, ArrayList<Map<String,String>> passtocheck) {
        this.bet = bet;
        this.passtocheck = passtocheck;

    }


    public HashMap<String,String> checkbetoutcome() {
        new LoadAllGamet(onResultListener lister).execute();
        return finaloutcomes;
    }
    public interface onResultListener {
        void showResult(HashMap<String,String> finaloutcomes);
    }


    class LoadAllGamet extends AsyncTask<String, String, String> {
        onResultListener listener;
        public LoadAllGamet(onResultListener listr) {
            listener = listr;
        }
        @Override
        protected void onPreExecute() {
            super.onPreExecute();

        }

        protected String doInBackground(String... args) {
           // HttpParams httpParameters = new BasicHttpParams();
           // HttpConnectionParams.setConnectionTimeout(httpParameters, 250000);
            //HttpConnectionParams.setSoTimeout(httpParameters, 250000);
            HttpClient client = new DefaultHttpClient();
            HttpPost post = new HttpPost(url_check_bet);
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("param", bet));
           // Log.d("CURRENTITEM", currentitem);
            try {
                post.setEntity(new UrlEncodedFormEntity(params));
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
            try {
                HttpResponse response = client.execute(post);
                Log.d("Http Post Responsecxxx:", response.toString());
                HttpEntity httpEntity = response.getEntity();
                InputStream is = httpEntity.getContent();
                JSONObject jObj = null;
                String json = "";
                client.getConnectionManager().closeExpiredConnections();
                try {
                    BufferedReader reader = new BufferedReader(new InputStreamReader(
                            is, "iso-8859-1"), 8);
                    StringBuilder sb = new StringBuilder();
                    String line = null;
                    while ((line = reader.readLine()) != null) {

                        if (!line.startsWith("<", 0)) {
                            if (!line.startsWith("(", 0)) {
                                sb.append(line + "\n");
                            }
                        }
                    }

                    is.close();
                    json = sb.toString();

                    json = json.substring(json.indexOf('{'));
                //    Log.d("sbsssssssssss", json);
                    try {
                        jObj = new JSONObject(json);
                    } catch (JSONException e) {
                        Log.e("JSON Parser", "Error parsing data " + e.toString());
                    }
                    allgames = jObj.getJSONArray("bets");
                 //   Log.d("WHAT IS MY ARRAY?", allgames.toString());

                       for (Integer i = 0; i < allgames.length(); i++) {
                           HashMap<String,String> statuses = new HashMap<>();
                            JSONObject c = allgames.getJSONObject(i);
                            JSONArray currentbet = c.getJSONArray("bet");
                            Log.d("Single array",currentbet.toString());

                           //  Storing each json item in variable

                           for (Integer a = 0; a < currentbet.length();a++) {
                               JSONObject d = currentbet.getJSONObject(a);
                            String Result = d.getString("Result");
                               String id = d.getString("gid");
                            Log.d("RESULTS",Result);

                           statuses.put(id, Result);
                        }
                           allbetsmap.add(i, statuses);
                           Log.d("ddd", statuses.toString());
                           Log.d("AAA", allbetsmap.get(i).toString());


                       }



                    } catch (Exception e) {
                        Log.e("Buffer Error", "Error converting result " + e.toString());
                    }


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




            return "";
        }



        @Override
        protected void onPostExecute(String param) {
            Log.d("SIZE",Integer.toString(allbetsmap.size()));
            //ArrayList<Map<String,String>> allbetsmap = new ArrayList<>();
            //ArrayList<Map<String,String>> passtocheck = new ArrayList<>();

            if (allbetsmap.size() == passtocheck.size()) {
                for (int i = 0; i < allbetsmap.size();i++) {
                if (allbetsmap.get(i).size() == passtocheck.get(i).size()) {
                    String finaloutcome = "won";
                    for (String a : allbetsmap.get(i).keySet()) {
                        String f = allbetsmap.get(i).get(a);
                        if(f.equals("null")) {
                            finaloutcome = "open";
                        }
                        else if (! (f.equals(passtocheck.get(i).get(a)))) {
                            finaloutcome = "lost";
                            break;
                        }
                    }
                    finaloutcomes.put(Integer.toString(i),finaloutcome);
                }
            }
        }
            Log.d("Vital",finaloutcomes.toString());
            listener.showResult(finaloutcomes);

        }

    }

        // CHANGE THIS AT THE END
    }

**

Answer 1

您已经知道AysncTask 异步运行，因此new LoadAllGamet().execute(); 将立即返回，因此finaloutcomes 将具有您存储在其中的最后一个值。

对于您想要更新调用者（AsyncTask）组件（例如 Activity）的这种情况，您应该使用侦听器。

请参阅帖子here，了解如何定义和使用侦听器，基本上是在AsyncTask 中定义的接口，其方法由您的调用者组件（例如Activity）使用适当的参数（值您在onPostExecute 中获得并传递给Activity）。

希望这会有所帮助！

Answer 2

创建界面

public interface onResultListener {
    void showResult(String finalOutcome);
}

Activity 实现接口

public MyActivity extends Activity implements onResultListener {
    public void getResult() {
        new LoadAllGamet(this).execute();
    }

    void showResult(String finalOutcome){
        // result from your asynctask  
    }
} 

从 AsyncTask 调用接口方法

 public class LoadAllGamet extends AsyncTask<String, String, String> {
    onResultListener listener;
    public LoadAllGamer(OnResultListenre listr) {
    listener = listr;

    @Override
    protected void onPostExecute(String param) {

        Log.d("SIZE",Integer.toString(allbetsmap.size()));
        //ArrayList<Map<String,String>> allbetsmap = new ArrayList<>();
        //ArrayList<Map<String,String>> passtocheck = new ArrayList<>();

        if (allbetsmap.size() == passtocheck.size()) {
            for (int i = 0; i < allbetsmap.size();i++) {
                if (allbetsmap.get(i).size() == passtocheck.get(i).size()) {
                    String finaloutcome = "won";
                    for (String a : allbetsmap.get(i).keySet()) {
                        String f = allbetsmap.get(i).get(a);
                        if(f.equals("null")) {
                            finaloutcome = "open";
                        }
                        else if (! (f.equals(passtocheck.get(i).get(a)))) {
                            finaloutcome = "lost";
                            break;
                        }
                    }
                    finaloutcomes.put(Integer.toString(i),finaloutcome);
                }
            }
        }
        Log.d("Vital",finaloutcomes.toString());
         lister.showResult(finalOutCome);
    }
}