如何在 android 中保存 HashMap 的列表？

Question

I have a hashmap of string

HashMap<String, String> hashMap = new HashMap<>();
hashMap.put("name", name);
hashMap.put("number", number);
hashMap.put("profileImage", image);

and a List of Hashmap

List<HashMap<String, String>> recents = new ArrayList<>();
recents.add(hashMap);

Now I have to save this list

I have tried using https://github.com/pilgr/Paper to save this List

Paper.book().write("recents", recents);

but i can't get the list back

List<HashMap<String, String>> list = Paper.book().read("recents");
HashMap<String,String> hashMap = list.get(0);
String name = hashMap.get("name");
String number = hashMap.get("number");
String image = hashMap.get("profileImage");

Uses of the code

actually I'm passing this list to recycelerViewAdapeter and from there in OnBindViewHolder() I'm getting all the Hashmap values and displaying it to user

Saving Data Code

Paper.init(this);
List<HashMap<String, String>> recents = new ArrayList<>();
HashMap<String, String> hashMap = new HashMap<>();
hashMap.put("name", name);
hashMap.put("number", number);
hashMap.put("profileImage", image);
recents.add(hashMap);
Paper.book().write("recents", contacts);

Receiving Data Code

Paper.init(requireActivity());
recyclerView = view.findViewById(R.id.recyclerView);
List<HashMap<String, String>> list = Paper.book().read("recents");
Adapter = new Adapter(requireActivity(), list);
recyclerView.setAdapter(Adapter);

Answer 1

You can use Gson and SharedPreferences to do the same.

implementation 'com.google.code.gson:gson:2.8.9'

Example:

private SharedPreferences sp;
private HashMap<String, Boolean> favs;
....
....
public void addFavourite(String wall_name) {
    favs = getFavourites();
    favs.put(wall_name, true);
    setFavourties();

}

public void removeFav(String wall_name) {
    favs = getFavourites();
    favs.put(wall_name, false);
    setFavourties();
}

private void setFavourties() {
    SharedPreferences.Editor pe = sp.edit();
    Gson gson = new Gson();
    String j = gson.toJson(favs);
    pe.putString("Favourites", j);
    pe.apply();
}


public HashMap<String, Boolean> getFavourites() {
    Gson gson = new Gson();
    String j = sp.getString("Favourites", null);
    if (j != null) {
        Type stringBooleanMap = new TypeToken<HashMap<String, Boolean>>() {
        }.getType();
        return gson.fromJson(j, stringBooleanMap);
    } else {
        return new HashMap<>();
    }
}