使用共享偏好来存储阵列列表，空对象返回

Question

我有一个ArrayList列表作者，我使用此AsyncTask填充。

class LoadAllGamesWhenNull extends AsyncTask<String, String, String> { 
    private String id; 
    private String stake; 
    private String user; 
    private String returns; 
    private String teams; 
    private String status; 


    // *//** 
    // * Before starting background thread Show Progress Dialog 
    // *//* 
    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 

    } 

    // *//** 
    // * getting All products from url 
    // *//* 
    protected String doInBackground(String... args) { 
     // Building Parameters 
     HttpClient client = new DefaultHttpClient(); 
     HttpPost post = new HttpPost(url_all_games); 
     List<NameValuePair> params = new ArrayList<NameValuePair>(); 
     params.add(new BasicNameValuePair("email", name)); 
     try { 
      post.setEntity(new UrlEncodedFormEntity(params)); 
     } catch (IOException ioe) { 
      ioe.printStackTrace(); 
     } 
     try { 
      HttpResponse response = client.execute(post); 
      Log.d("Http Post Response:", response.toString()); 
      HttpEntity httpEntity = response.getEntity(); 
      InputStream is = httpEntity.getContent(); 
      JSONObject jObj = null; 
      String json = ""; 
      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("sb", json); 

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

      // try parse the string to a JSON object 
      try { 
       jObj = new JSONObject(json); 
      } catch (JSONException e) { 
       Log.e("JSON Parser", "Error parsing data " + e.toString()); 
      } 

      // return JSON String 
      Log.d("json", jObj.toString()); 
      try { 
       allgames = jObj.getJSONArray(TAG_BET); 
       Log.d("allgames", allgames.toString()); 
       ArrayList<BetDatabaseSaver> listofbets = new ArrayList<>(); 
       // looping through All Products 
       for (int i = 0; i < allgames.length(); i++) { 
        JSONObject c = allgames.getJSONObject(i); 

        // Storing each json item in variable 
        String id = c.getString(TAG_ID); 
        String user = c.getString(TAG_USER); 
        String returns = c.getString(TAG_RETURNS); 
        String stake = c.getString(TAG_STAKE); 
        String status = c.getString(TAG_STATUS); 
        String Teams = c.getString(TAG_TEAMS); 
        Log.d("id", id); 
        Log.d("user", user); 
        Log.d("returns", returns); 
        Log.d("stake", stake); 
        Log.d("status", status); 
        Log.d("teams", Teams); 


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

        // adding each child node to HashMap key => value 
        map.put(TAG_ID, id); 
        map.put(TAG_TEAMS, Teams); 
        map.put(TAG_USER, user); 
        map.put(TAG_RETURNS, returns); 
        map.put(TAG_STAKE, stake); 
        map.put(TAG_STATUS, status); 
        if (status.equals("open")) { 
         useroutcomes.put(id.substring(0, 10), Teams); 
        } 

        listwriter.add(i, new BetDisplayer(user, id, Integer.parseInt(stake), Integer.parseInt(returns), status, "","",Teams)); 

        Log.d("map", map.toString()); 
        // adding HashList to ArrayList 
        bet.add(map); 
       } 


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


     return ""; 
    } 


    @Override 
    protected void onPostExecute(String param) { 


     // dismiss the dialog after getting all products 
     // updating UI from Background Thread 
     String ultparam = ""; 
     int i = 0; 
     for (HashMap<String, String> a : bet) { 
      String teams = a.get(TAG_TEAMS); 

      Map<String, String> listofteams = new HashMap<>(); 

      Pattern p = Pattern.compile("[(](\\d+)/([1X2])[)]"); 
      Matcher m = p.matcher(teams); 
      Log.d("printa", teams); 
      while (m.find()) { 
       listofteams.put(m.group(1), m.group(2)); 
      } 
      Log.d("dede", listofteams.toString()); 
      String c = ""; 
      for (String x : listofteams.keySet()) { 
       String b = x + ","; 
       c = c + b; 
      } 
      Log.d("C", c); 
      c = c.substring(0, c.lastIndexOf(",")); 
      // Log.d("Cproc", c); 

       ultparam = ultparam + a.get(TAG_ID).substring(0, 10) + c + "//"; 
       passtocheck.add(listofteams); 
       allopens.put(Integer.toString(i), a.get(TAG_STATUS)); 
       i++; 

      i++; 

     } 
     ultparam = ultparam.substring(0, ultparam.lastIndexOf("//")); 
     Log.d("ULTPARAM", ultparam); 
     CheckBet checker = new CheckBet(ultparam, passtocheck); 
     HashMap<String, String> finaloutcomes = checker.checkbetoutcome(); 
     Log.d("Finaloutcomes", finaloutcomes.toString()); 
     finaloutcomess = finaloutcomes.toString(); 
     for (String x : finaloutcomes.keySet()) { 
      for (int p = 0; p < listwriter.size(); p++) { 
       if (listwriter.get(p).getId().substring(0, 10).equals(x)) { 
        String[] finaloutcomearray = finaloutcomes.get(x).split(" "); 
        String[] useroutcomearray = listwriter.get(p).getSelections().split(" "); 
        for (int r = 0; r < finaloutcomearray.length; r++) { 
         Log.d("finaloutcomearray", finaloutcomearray[r]); 
         Log.d("useroutcomearray", useroutcomearray[r]); 
         String[] indfinaloutcomesarray = finaloutcomearray[r].split("\\)"); 
         String[] induseroutcomearray = useroutcomearray[r].split("\\)"); 
         for (int d = 0; d < indfinaloutcomesarray.length; d++) { 
          Log.d("indfinaloutcome", indfinaloutcomesarray[d]); 
          Log.d("induseroutcome", induseroutcomearray[d]); 
          finalhash.put(indfinaloutcomesarray[d].substring(1, indfinaloutcomesarray[d].lastIndexOf("/")), indfinaloutcomesarray[d].substring(indfinaloutcomesarray[d].lastIndexOf("/") + 1)); 
          userhash.put(induseroutcomearray[d].substring(1, induseroutcomearray[d].lastIndexOf("/")), induseroutcomearray[d].substring(induseroutcomearray[d].lastIndexOf("/") + 1)); 

         } 
        } 
        Log.d("FINALHASHfinal", finalhash.toString()); 
        listwriter.get(p).setActualselections(finalhash.toString()); 
        listwriter.get(p).setUserselections(userhash.toString()); 
        Log.d("USERHASHfinal", userhash.toString()); 
        listwriter.get(p).setStatus("won"); 
        for (String id : userhash.keySet()) { 
         if (finalhash.get(id).equals("null")) { 
          listwriter.get(p).setStatus("open"); 
         } else if (!(finalhash.get(id).equals(userhash.get(id)))) { 
          listwriter.get(p).setStatus("lost"); 
          break; 
         } 

        } 
        finalhash.clear(); 
        userhash.clear(); 
        currentitem = listwriter.get(p); 
        if (currentitem.getStatus().equals("open")) { 

        } else { 
         if (currentitem.getStatus().equals("won")) { 
          valuechange = valuechange + currentitem.getReturns() - (currentitem.getStake()); 
         } 
         String c = currentitem.getId() + "," + currentitem.getStatus() + "//"; 
         updateparam = updateparam + c; 
         Log.d("UPDATEPARAM1", updateparam); 
        } 
       } 
      } 
     } 
     Log.d("Listwriterbefore",listwriter.toString()); 
     session.setListwriter(listwriter); 
     new UpdateBetStatus().execute(); 
     Intent g = new Intent(loadingscreen.this,DisplayAllBets.class); 
     startActivity(g); 
     finish(); 
    }} 

这是对我的loadscreen Activity做，我想将listwriter设置为我的SharedPreferences，这样我可以在其他Activity使用它。这是我的会话管理员类。 AsyncTask中的日志记录向我显示，列表作者正确填充。但是，当我打电话给另一班的getlistwriter时，我收到一个空的ArrayList。我看不到错误在哪里。

public class SessionManager { 
// LogCat tag 
private static String TAG = SessionManager.class.getSimpleName(); 
private ArrayList<BetDisplayer> listwriter = new ArrayList<>(); 
// Shared Preferences 
SharedPreferences pref; 

Editor editor; 
Context _context; 

// Shared pref mode 
int PRIVATE_MODE = 0; 

// Shared preferences file name 
private static final String PREF_NAME = "AndroidHiveLogin"; 

private static final String KEY_IS_LOGGEDIN = "isLoggedIn"; 

public static final String USERNAME = "username"; 


public SessionManager(Context context) { 
    this._context = context; 
    pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE); 
    editor = pref.edit(); 
} 

public ArrayList<BetDisplayer> getListwriter() { 
    return listwriter; 
} 

public void setListwriter(ArrayList<BetDisplayer> listwriter) { 
    this.listwriter = listwriter; 
} 

public void setLogin(boolean isLoggedIn, String username) { 

    editor.putBoolean(KEY_IS_LOGGEDIN, isLoggedIn); 
    editor.putString(USERNAME, username); 

    // commit changes 
    editor.commit(); 

    Log.d(TAG, "User login session modified!"); 
} 

public HashMap<String, String> getUserDetails(){ 
    HashMap<String, String> user = new HashMap<String, String>(); 
    // user name 
    user.put(USERNAME, pref.getString(USERNAME, null)); 

    // return user 
    return user; 
} 
public boolean isLoggedIn(){ 
    return pref.getBoolean(KEY_IS_LOGGEDIN, false); 
}} 

代码用于检索listwriter

public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState);  
setContentView(R.layout.activity_display_all_bets); 
menu menu = (menu) 
getFragmentManager().findFragmentById(R.id.fragment); 
menu.updateinfo(getName()); 
session = new SessionManager(getApplicationContext()); 
    HashMap<String, String> user = session.getUserDetails(); 
    name = user.get(SessionManager.USERNAME); 
    listwriter = session.getListwriter(); 

的AppController类：

public class AppController extends Application { 

public static final String TAG = AppController.class.getSimpleName(); 

private RequestQueue mRequestQueue; 

private static AppController mInstance; 

private ArrayList<HashMap<String, String>> gamesList; 

public ArrayList<HashMap<String, String>> getGamesList() { 
    return gamesList; 
} 

public void setGamesList(ArrayList<HashMap<String, String>> gamesList) { 
    this.gamesList = gamesList; 
} 

@Override 
public void onCreate() { 
    super.onCreate(); 
    mInstance = this; 
} 


public static synchronized AppController getInstance() { 
    return mInstance; 
} 

public RequestQueue getRequestQueue() { 
    if (mRequestQueue == null) { 
     mRequestQueue = Volley.newRequestQueue(getApplicationContext()); 
    } 

    return mRequestQueue; 
} 

public <T> void addToRequestQueue(Request<T> req, String tag) { 
    req.setTag(TextUtils.isEmpty(tag) ? TAG : tag); 
    getRequestQueue().add(req); 
} 

public <T> void addToRequestQueue(Request<T> req) { 
    req.setTag(TAG); 
    getRequestQueue().add(req); 
} 

public void cancelPendingRequests(Object tag) { 
    if (mRequestQueue != null) { 
     mRequestQueue.cancelAll(tag); 
    } 
} 

Answer 1

在你SessionManager你不保存您的List到SharedPrefs。你应该做这样的事情：

public static final String MY_LIST = "my_list"; 
private static final Type LIST_TYPE = new TypeToken<List<BetDisplayer>>() {}.getType(); 

保存：

public void setListwriter(ArrayList<BetDisplayer> listwriter) { 
    this.listwriter = new ArrayList<BetDisplayer>(listwriter); 
    mPrefs.edit() 
      .putString(MY_LIST, new Gson().toJson(listwriter)); 
      .commit(); 
} 

加载：

public ArrayList<BetDisplayer> getListwriter() { 
    if (listwriter == null) { 
     listwriter = new Gson().fromJson(mPrefs.getString(MY_LIST, null), LIST_TYPE); 
     if(listwriter == null){ 
      listwriter = new ArrayList<BetDisplayer>(); 
     } 
    } 
    return listwriter; 
} 

你BetDisplayer必须implements Serializable。
在这里看到：Android array to Sharedpreferences with Gson

要使用Gson只需添加这种依赖关系： 'com.google.code.gson：GSON：2.3.1' 或下载.jar

UPDATE： 创建Singleton那只有你的SharedPreferences编辑器，这只是一个猜测，但我认为你使用不同的上下文来获得你的编辑器，这可能是问题（更新2：它不是，检查here，但Singleton接近它是一个加）：

private static SharedPreferences mPrefs; 
private static SessionManager sInstance = null; 

protected SessionManager() { 
    mPrefs = AppController.getInstance().getApplicationContext().getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE); 
} 

public static SessionManager getInstance() { 
    if (sInstance == null) { 
     sInstance = new SessionManager(); 
    } 
    return sInstance; 
} 

而当你需要使用SharedPreferences使用SessionManager().getInstance().someMethod();