Best practice for Android MVVM startActivity

Question

I am building an Android App using MVVM and DataBinding. And I have a function inside my ViewModel that starts an Activity. Is it okay to have an onClick call inside a ViewModel

Answer 1

in MVVM we can use LiveData for this Event . because ViewModel is Alive when the activity/Fragment destroyed! So the best way is LiveData

1.Create Class Call Event and Extends It from ViewModel:

class Event : ViewModel() {

2.create field from LiveData :

private val _showSignIn = MutableLiveData()

3.create method for this private field:

val showSignIn: LiveData
    get() = _showSignIn

4.create method that you can setValue on your liveData:

 fun callSignIn() {
        _showSignIn.value = true
    }

The final Event Class :

import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel

class Event : ViewModel() {

     private val _showSignIn = MutableLiveData()

        val showSignIn: LiveData
            get() = _showSignIn

        fun callSignIn() {
            _showSignIn.value = true
        }

5. Call the method in your activity or fragment :

THe instance from eventViewModel :

 private val eventViewModel = Event()

call the observe :

 eventViewModel.showSignIn.observe(this, Observer {
            startActivity(Intent(this, MainActivity::class.java))
        })

and if you use the data binding you can call callSignIn() in onClick XML :

in Variable tag:

 android:onClick="@{() -> eventViewModel.callSignIn()}" 

NOTE: do not forget set binding in your activity/fragment :

  binding.eventViewModel = eventViewModel

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I search for the best way and Find it. I hope to help someone