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

When using MVVM and LiveData, you can re-bind the object to the layout so it will trigger all changes on the UI.

Given "user" is a MutableLiveData in the ViewModel

ViewModel

class SampleViewModel : ViewModel() {
    val user = MutableLiveData()

    fun onChange() {
        user.value.firstname = "New name"
        user.value = user.value // force postValue to notify Observers
        // can also use user.postValue()
    }
}

Activity/Fragment file:

viewModel = ViewModelProviders
            .of(this)
            .get(SampleViewModel::class.java)

// when viewModel.user changes, this observer get notified and re-bind
// the user model with the layout.
viewModel.user.observe(this, Observer {
    binding.user = it //<- re-binding user
})

Your layout file shouldn't change:

    


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