如何在 SharedPreferences 中存储 <HashMap<MyCompositeKeyClass, ArrayList<MyClass>>？答案

【问题标题】：How can I store a <HashMap<MyCompositeKeyClass, ArrayList<MyClass>> in SharedPreferences?如何在 SharedPreferences 中存储 <HashMap<MyCompositeKeyClass, ArrayList<MyClass>>？
【发布时间】：2015-04-10 11:40:32
【问题描述】：

我希望在 SharedPreferences 中存储一个包含 MyCompositeKeyClass 作为键和 ArrayList 作为值的 HashMap。我该怎么做？

我试过这个：

 public void saveLessonMap(Context context, HashMap<dayKey, ArrayList<Lesson>> lessonMap){
   MapWrapper wrapper = new MapWrapper(lessonMap);
   String serializedMap = gson.toJson(wrapper);

    appSharedPrefs = PreferenceManager
            .getDefaultSharedPreferences(context);

    SharedPreferences.Editor prefsEditor = appSharedPrefs.edit();

    prefsEditor.putString(KEY, serializedMap);
    prefsEditor.commit();


}

 public HashMap<dayKey, ArrayList<Lesson>> getLessonMap(Context context){
    appSharedPrefs = PreferenceManager
            .getDefaultSharedPreferences(context);
    String wrapperStr = appSharedPrefs.getString(KEY, "");
    MapWrapper wrapper = gson.fromJson(wrapperStr, MapWrapper.class);
    return wrapper.getMap();
}

但是得到了：

fromJson com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 10

JSON：{"map":{"com.example.ruslanposhuk.timetable.model.dayKey@ca81be1c":[{"bTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":8,"minute":30,"second":0},"eTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":9,"minute":50,"second":0},"name":"Wednesday1","room":"114","teacherName":"John Smith"},{"bTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":10,"minute":0,"second":0},"eTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":11,"minute":20,"second":0},"name":"Wednesday2","room":"254","teacherName":"Bob Moore"},{"bTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":12,"minute":0,"second":0},"eTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":13,"minute":20,"second":0},"name":"Wednesday3","room":"178","teacherName":"Peter Johnson"}],"com.example.ruslanposhuk.timetable.model.dayKey@28f78912":[{"bTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":8,"minute":30,"second":0},"eTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":9,"minute":50,"second":0},"name":"Tuesday1","room":"114","teacherName":"John Smith"},{"bTime":{"year":2015,"month":4,"dayOfMonth":7,"hourOfDay":10,"minute":0,"second":0},"eTime"]}}

【问题讨论】：

标签： java android hashmap sharedpreferences gson

【解决方案1】：

将ArryList<MyClass>转换为json数据并存储。使用 gson 库将 ArrayList 转换为 JSON String 格式。

【讨论】：

【解决方案2】：

  Gson gson  =
        new GsonBuilder().enableComplexMapKeySerialization().setPrettyPrinting().create();
java.lang.reflect.Type type = new TypeToken <HashMap<dayKey, ArrayList<Lesson>>>(){}.getType();

保存：String json = gson.toJson(lessonMap, type);

加载中：HashMap<dayKey, ArrayList<Lesson>> lessonMap = gson.fromJson(json, type);

【讨论】：