如何将 Map 保存到共享首选项？

Question

I have an Map<Integer, User> with custom values. Each User contains variety of strings and numbers. I can save a singel User but safe the entire Map is difficult. (I save a lot of other objects this way by using the SharedPreferences but I can't figure out how to save my entire Map this way. Is this possible? Maybe SharedPreferences isn't the way to go about this? Is there a simpler method?)

Shared Preference Class:

Map

public void saveUserMap(Map<Integer, User> userMap){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();

        editor.putInt("userID", userMap.get(userMap).getUserID());
        editor.putString("firstName", userMap.get(userMap).getFirstName());
        editor.putString("userName", userMap.get(userMap).getUserName());
        editor.putString("birthDate", userMap.get(userMap).getBirthDate());
        editor.putString("gender", userMap.get(userMap).getGender());
        editor.putString("country", userMap.get(userMap).getCountry());
        editor.putString("aboutmeText", userMap.get(userMap).getAboutmeText());
        editor.putString("status", userMap.get(userMap).getStatus());

        editor.apply();
    }

Single User:

public void saveUser(User user){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();

        editor.putInt("userID", user.getUserID());
        editor.putString("firstName", user.getFirstName());
        editor.putString("userName", user.getUserName());
        editor.putString("birthDate", user.getBirthDate());
        editor.putString("gender", userMap.get(userMap).getGender());
        editor.putString("country", user.getCountry());
        editor.putString("aboutmeText", user.getAboutmeText());
        editor.putString("status", user.getStatus());
       
        editor.apply();
}

Save a Single User is possible:

SharedPrefManager.getInstance(TestRequest.this)
                            .saveUser(standardResponse.getUser().get(0));

Save User Map crash:

SharedPrefManager.getInstance(TestRequest.this)
                            .saveUserMap(standardResponse.getUser());

Answer 1

You can serialise user object to json(using GSON or Moshi) and save the JSON into shared Pref.

public void saveUserMap(User user){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();

        editor.putString("mUser", new Gson().toJson(user));

        editor.apply();
    }

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Other options for save objects are a number of ORMs for Android (ORMLite, greenDAO, Sugar ORM, ActiveAndroid, etc.)