How to save objects list in Android

Question

I want to save this list (List) after exiting the application, and when running again I want to recover the instance from the list that was previously saved.

private List<BluetoothDevice> listaDispositivoFavorito = new ArrayList<BluetoothDevice>();

Answer 1

There are some ways to record/persist data on Android to retrieve it later, as demonstrated here in the documentation:

The most commonly used are:

Sharedpreferences

Which is a place where you can store values primitive, key-value format (key-value pairs).

In your case you can serialize the object in json (in String), and retrieve and deserialize it later.

You can use the library gson to serialize and deserialize the object.

To save:

SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);
Editor prefsEditor = mPrefs.edit();
Gson gson = new Gson();
String json = gson.toJson(listaDispositivoFavorito );
prefsEditor.putString("DISPOSITIVOS", json);
prefsEditor.commit();

To recover:

SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);
Gson gson = new Gson();
String json = mPrefs.getString("DISPOSITIVOS", "");
Type type = new TypeToken<List<BluetoothDevice>>(){}.getType();
List<BluetoothDevice> obj = gson.fromJson(json, type);

Sqlite Databases

Which is an SQL database for Android. How to use here.

References:

1. http://developer.android.com/guide/topics/data/data-storage.html#pref
2. http://developer.android.com/guide/topics/data/data-storage.html#db
3. https://stackoverflow.com/questions/7145606/how-android-sharedpreferences-save-store-object
4. https://stackoverflow.com/questions/20819294/save-custom-object-array-to-shared-preferences
5. https://stackoverflow.com/questions/14981233/android-arraylist-of-custom-objects-save-to-sharedpreferences-serializable