onClick 与 dataBinding ViewModel 不起作用

Question

Im working on a project and implementing the MVVM model with databinding and navigation . My button is on a fragment that opens with a drawer menu item , the thing is when i click on the button it does nothing, the debugger doesn't go into the navigate method, I really don't know what I did wrong, can someone help?

MYACCOUNT CLASS :

class MyAccountFragment : BaseFragment() {

    private val vm: MyAccountViewModel by viewModel()


    override fun getViewModel(): BaseViewModel = vm

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding = FragmentMyAccountBinding.inflate(inflater, container, false)
        context ?: return binding.root
        injectFeature()

        setToolbar(binding)
        subscribeUi(binding)

        return binding.root
    }

    /**
     * set toolbar
     * **/
    private fun setToolbar(binding: FragmentMyAccountBinding) {

        binding.appBarLayout.backClickListener = (activity as MainActivity).createOnBackClickListener()
    }

    /**
     * set ui
     * **/
    private fun subscribeUi(binding: FragmentMyAccountBinding) {
        binding.viewModel = vm
    }


}

MYACCVIEWMODEL

class MyAccountViewModel constructor() : BaseViewModel() {

    fun onAddRoomClick()
    {
        navigate(MyAccountFragmentDirections.actionMyAccountFragmentToAddRoomFragment())
    }
}

and in the xml i implemented the

android:onClick="@{() -> viewModel.onAddRoomClick()}"

Im using this pattern for all my Fragments and ViewModels , and i really dont know why it doesn't do anything, the vm initializes. On the other drawermenu fragment I also have the onClick method and it navigates to the other fragment. So if anyone knows the solution that would be helpful, thank you in advance.

Answer 1

the answer was in the initialization of the viewModel.

the onClick method in xml is in a content_layout that is included in a fragment_layout and instead of binding.viewModel = vm I had to do binding.content_layout.viewModel = vm.

 private fun subscribeUi(binding: FragmentMyAccountBinding) {
        binding.contentMyAccount.viewModel = vm
    }

Answer 2

ViewModel is not supposed to handle any kind of navigation, it will just receive the event from the UI and pass it to the controller (which might be a fragment or activity) and the latter will handle the navigation...

So one way to solve your issue is to do the following:

ViewModel

   class MyAccountViewModel constructor() : BaseViewModel() {
private val _navigateToRoomFragEvent = MutableLiveData<Boolean>(false)
val navigateToRoomFragEvent:LiveData<Boolean>
    get()=_navigateToRoomFragEvent

fun onAddRoomClick()
{
    _navigateToRoomFragEvent.value=true
}
fun resetNavigation(){
    _navigateToRoomFragEvent.value=false
}

}

Controller (Activity or Fragment)

inside **onCreate() (if it is an activity)**

viewModel.navigateToRoomFragEvent.observe(this,Observer{navigate->
//boolean value
if(navigate){
navController.navigate(//action)
}
viewModel.resetNavigation() //don't forget to reset the event
})

onActivityCreated(if it is a fragment)

viewModel.navigateToRoomFragEvent.observe(viewLifeCycleOwner,Observer{navigate->
//boolean value
if(navigate){
navController.navigate(//action)
}
viewModel.resetNavigation() //don't forget to reset the event
})

Hope it helps,