DataBinding like accessing Model Fields in Layout.

fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto">
    <data>
        <import type="java.lang.Integer" />

        <variable name="vm" type="app.example.vmdb_sample.MainViewModel" />

    </data>
    <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            tools:showIn="@layout/activity_main"
            tools:context=".MainActivityFragment">

        <TextView
                android:text="@{vm.userLiveData.name}"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/textViewUserName"
                app:layout_constraintStart_toStartOf="parent" app:layout_constraintHorizontal_bias="0.5"
                app:layout_constraintEnd_toStartOf="@+id/textViewUserAge" android:layout_marginTop="52dp"
                app:layout_constraintTop_toTopOf="parent"/>
        <TextView
                android:text="@{Integer.toString(vm.userLiveData.age)}"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/textViewUserAge" app:layout_constraintStart_toEndOf="@+id/textViewUserName"
                app:layout_constraintHorizontal_bias="0.5" app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintBaseline_toBaselineOf="@+id/textViewUserName"/>
        <Button
                android:text="Button"
                android:onClick="@{() -> vm.load()}"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/button" android:layout_marginTop="8dp"
                app:layout_constraintTop_toBottomOf="@+id/textViewUserName" android:layout_marginBottom="8dp"
                app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintStart_toStartOf="parent"
                android:layout_marginStart="8dp" app:layout_constraintEnd_toEndOf="parent"
                android:layout_marginEnd="8dp"
                app:layout_constraintHorizontal_bias="0.21" app:layout_constraintVertical_bias="0.51"/>
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

MainActivityFragment.kt

class MainActivityFragment : androidx.fragment.app.Fragment() {

    val viewModel = MainViewModel()
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding = FragmentMainBinding.inflate(inflater)
        binding.setLifecycleOwner(this)
        binding.vm = viewModel
        return binding.root
    }
}

class MainViewModel : ViewModel() {
    val handler: Handler = Handler()
    val userLiveData = UserLiveData("Bar", 22)
    fun load() {

        Executors.newSingleThreadExecutor().execute {
            updateUser((User("Foo", 50)))
        }

    }

    private fun updateUser(user: User) {
        handler.post {
            Log.d("aaa", "load:$user")
            userLiveData.value = user
        }
    }

}

data class User(val name: String, val age: Int)

class UserLiveData(val defaultName: String, val defaultAge: Int) {
    val userLiveData = MutableLiveData<User>()

    val name = MediatorLiveData<String>().apply { value = defaultName }
    val age = MediatorLiveData<Int>().apply { value = defaultAge }

    init {
        name.addSource(userLiveData) { liveData: User -> name.value = liveData.name }
        age.addSource(userLiveData) { liveData: User -> age.value = liveData.age }
    }

    var value: User = User(defaultName, defaultAge)
        set(value) {
            if (value == field) return
            field = value
            name.value = value.name
            age.value = value.age
        }

    fun post(user: User) {
        name.postValue(user.name)
        age.postValue(user.age)
    }

}