How to retrieve users from a LiveData List to display in a Spinner using Room Database

Question

I've been following several guides most recently this one from CodeLabs to try and create a Room Database for my app. All of the guides I've been using use a Recycler View. I'm trying to figure out how to use this data and implement it in a different type of components but a Spinner for now to display the users.

I've got my entity, dao, database, repository and view model all created and I think sitting correctly.

My adapter differs from the guide as they use code that is for a recyler view. Where as I want my data to appear in a spinner.

class UserListAdapter {

private List<Users> mUser = Collections.emptyList(); // Cached copy of words


void setUser(List<Users> user){
    mUser = user;
}

// getItemCount() is called many times, and when it is first called,
// mWords has not been updated (means initially, it's null, and we can't return null).
public int getItemCount() {
    if (mUser != null)
        return mUser.size();
    else return 0;
}}

Where as here is the CodeLabs adapter. I just removed everything related to recyler view and used the remaining code for my adapter.

I have default values "Hello", "World" pre-populating the database during the build in the database class, here's that method:

private static class PopulateDbAsync extends AsyncTask<Void, Void, Void> {

    private final UsersDao mDao;

    PopulateDbAsync(AppDatabase db) {
        mDao = db.usersDao();
    }

    @Override
    protected Void doInBackground(final Void... params) {
        mDao.deleteAll();
        Users user = new Users("Hello");
        mDao.insertNewUser(user);
        user = new Users("World");
        mDao.insertNewUser(user);
        return null;
    }
}
}   

I have a method which inserts the data into the spinner:

private void createSpinners(ArrayList<String> listToUse) {
    ArrayAdapter<String> adp1 = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1, listToUse);
    spin_PlayerSelection.setAdapter(adp1);

}

In the onCreate code block I want to retrieve the List of users and pass it to the above method.

final UserListAdapter adapter = new UserListAdapter();
    mUsersViewModel = ViewModelProviders.of(this).get(UsersViewModel.class);

    mUsersViewModel.getAllUsers().observe(this, new Observer<List<Users>>() {
        @Override
        public void onChanged(@Nullable final List<Users> user) {
            // Update the cached copy of the words in the adapter.
            // Update scroll view here
            adapter.setUser(user);
            createSpinners(mUsersViewModel.getAllUsers());
        }
    });

As it stands now I'm getting the error:

Where am I going wrong?

Updated relecting @JohnJoe's reply:

I tried your way but getAllUsers doesn't have a .Size method because it is LiveData (I think). But I do have a getItemCount method in my UserListAdapter so i used this and then used the get name method in the Users Class which contains the Entity or table, to leave the code like so:

mUsersViewModel.getAllUsers().observe(this, new Observer<List<Users>>() {
        @Override
        public void onChanged(@Nullable final List<Users> user) {
            // Update the cached copy of the words in the adapter.
            // Update scroll view here
            adapter.setUser(user);
            for (int i = 0; i < adapter.getItemCount(); i++) {
                playerNames.add(String.valueOf(user.get(i)));
            }
            createSpinners(sortListAlphabetically(playerNames));
        }
    });

This returns values but not the names them selves as you can see in this image, but this is progress.

Answer 1

You need to create another ArrayList used to stored the data from mUsersViewModel.getAllUsers() .

For an example:

for(i<0;i<mUsersViewModel.getAllUsers().size; i++){
     list.add(user.xxx) // get user info here
}

Then only you can pass the list to createSpinner function.

createSpinners(list);

Based on your edited post, you are getting the list value. You should retrieve variables inside User class. Example: user.get(i).name where name is inside User class.