MVVM Architecture

MainActivity.kt

/**
 * Created by Dinorah Tovar on 18/01/19.
 * Main Activity that verify if the user is availbale
 */
class MainActivity : AppCompatActivity() {

    private var viewModel: MainViewModel? = null

    /**
     * On Create View instance
     * @param savedInstanceState Bundle?
     */
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)
        viewModel?.userLiveData?.observe(this, userLogin())
        viewModel?.userAvailable()
    }

    /**
     * Search for user available on the view
     */
    private fun userLogin() = Observer<Boolean> { existingUser ->
          if (existingUser) {
            startActivity(Intent(context, HomeActivity::class.java))
          } else {
            startActivity(Intent(context, LoginActivity::class.java))
          }
    }

}

MainViewModel.kt

/**
 * Created by Dinorah Tovar on 18/01/2019.
 * Main View model for the MainActivity class
 */
class MainViewModel : ViewModel() {

    @Inject
    internal lateinit var loginRepository: LoginRepository
  
    val userLiveData: MutableLiveData<Boolean> by lazy { MutableLiveData<Boolean>() }

    /**
     * Init injector for main class
     */
    init {
        YourMainApplication.appComponent?.inject(this)
    }

    /**
     * User available and observer Mutable live data object
     */
    fun userAvailable() {
        val user = loginRepository.currentUser()
        userLiveData.value = user?.let { true } ?: false
    }

}