Save ArrayList to SharedPreferences

Question

I have an ArrayList with custom objects. Each custom object contains a variety of strings and numbers. I need the array to stick around even if the user leaves

Answer 1

Use this custom class:

public class SharedPreferencesUtil {

    public static void pushStringList(SharedPreferences sharedPref, 
                                      List list, String uniqueListName) {

        SharedPreferences.Editor editor = sharedPref.edit();
        editor.putInt(uniqueListName + "_size", list.size());

        for (int i = 0; i < list.size(); i++) {
            editor.remove(uniqueListName + i);
            editor.putString(uniqueListName + i, list.get(i));
        }
        editor.apply();
    }

    public static List pullStringList(SharedPreferences sharedPref, 
                                              String uniqueListName) {

        List result = new ArrayList<>();
        int size = sharedPref.getInt(uniqueListName + "_size", 0);

        for (int i = 0; i < size; i++) {
            result.add(sharedPref.getString(uniqueListName + i, null));
        }
        return result;
    }
}

How to use:

SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
SharedPreferencesUtil.pushStringList(sharedPref, list, getString(R.string.list_name));
List list = SharedPreferencesUtil.pullStringList(sharedPref, getString(R.string.list_name));