LiveData update on object field change

Question

I\'m using Android MVVM architecture with LiveData. I have an object like this

public class User {
    private String firstName;
    private String lastName;         


        

Answer 1

For your observer get notified you should use setValue if you do this user.getValue().setFirstName(user.getValue().getFirstName() + " A "); your observer will not be notified !

View Model

public MutableLiveData getUser() {
    return user;
}

Activity / Fragment

mModel = ViewModelProviders.of(this).get(InfoViewModel.class);
mModel.getUser().observe(this, s -> {
    // User has been modified
});

Somewhere in your activity / fragment

This will trigger the observer :

mModel.getUser().setValue(user);

If you want to update only one field from an object instead of update the whole object you should have multiples MutableLiveData

// View Model
private MutableLiveData         firstName;
private MutableLiveData         lastName;

//Somewhere in your code
mModel.getFirstName().setValue(user.getValue().getFirstName() + " A ");
mModel.getFirstName().observe(this, s -> {
    // Firstname has been modified
});