ViewModel + DataBinding sample

activity_main.xml

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

    <data>
        <variable
            name="viewmodel"
            type="com.example.mvvmlab.MainViewModel" />
    </data>


    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{viewmodel.user.nickname}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

MainActivity.kt

package com.example.mvvmlab

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import androidx.databinding.ObservableBoolean
import androidx.databinding.ObservableField
import androidx.databinding.ObservableInt
import androidx.lifecycle.*
import com.example.mvvmlab.databinding.ActivityMainBinding
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch

class MainActivity : AppCompatActivity() {

    private val viewModel :MainViewModel by lazy {
        ViewModelProvider.NewInstanceFactory().create(MainViewModel::class.java)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val binding: ActivityMainBinding =
            DataBindingUtil.setContentView(this, R.layout.activity_main)
        binding.viewmodel = viewModel
        binding.lifecycleOwner = this
        viewModel.loadUser()
    }
}

class MainViewModel() : ViewModel() {

    private val liveDataUser = LiveDataUser()
    private val observableUser = ObservableUser()

    val user: LiveDataUser
        get() = liveDataUser

//    val user: ObservableUser
//        get() = observableUser


    fun loadUser() {
        viewModelScope.launch {
            delay(1000L)
            liveDataUser.apply {
                nickname.value = "タロー"
                firstName.value = "太郎"
                lastName.value = "山田"
                age.value = 22
                birthMonthOfYear.value = "11"
                birthDayOfMonth.value = "12"
                address.value = "東京都世田谷区"
                isPremium.value = false
            }
        }
    }


    fun loadUser2() {
        viewModelScope.launch {
            delay(1000L)
            observableUser.apply {
                nickname.set("タロー")
                firstName.set("太郎")
                lastName.set("山田")
                age.set(22)
                birthMonthOfYear.set("11")
                birthDayOfMonth.set("12")
                address.set("東京都世田谷区")
                isPremium.set(false)
            }
        }
    }
}


class ObservableUser {
    val nickname = ObservableField<String>()
    val firstName = ObservableField<String>()
    val lastName = ObservableField<String>()
    val age = ObservableInt()
    val birthMonthOfYear = ObservableField<String>()
    val birthDayOfMonth = ObservableField<String>()
    val address = ObservableField<String>()
    val isPremium = ObservableBoolean()
}


class LiveDataUser {
    val nickname = MutableLiveData<String>()
    val firstName = MutableLiveData<String>()
    val lastName = MutableLiveData<String>()
    val age = MutableLiveData<Int>()
    val birthMonthOfYear = MutableLiveData<String>()
    val birthDayOfMonth = MutableLiveData<String>()
    val address = MutableLiveData<String>()
    val isPremium = MutableLiveData<Boolean>()
}

なお、これでもいける

class MainViewModel() : ViewModel() {

    private val liveDataUser = MutableLiveData<User>()
    val user: LiveData<User>
        get() = liveDataUser

    fun loadUser() {
        viewModelScope.launch {
            delay(1000L)
            liveDataUser.value = User(
                nickname = "タロー",
                firstName = "太郎",
                lastName = "山田",
                age = 22,
                birthMonthOfYear = "11",
                birthDayOfMonth = "12",
                address = "東京都世田谷区",
                isPremium = false
            )
        }
    }
}

data class User (
    val nickname: String,
    val firstName: String,
    val lastName: String,
    val age: Int,
    val birthMonthOfYear: String,
    val birthDayOfMonth: String,
    val address: String,
    val isPremium: Boolean
)