Calling Mainactivity inside Viewmodel(updated)

Question

For the MVVM architecture, need to call a WebSocket variable in the ViewModel class.

And my WebSocket service is declared in the MainActivity.

So, MainActivity needs to be instantiated in the ViewModel.

I tried to declare an instance:: ''' (activity as MainActivity) ''' inside my ViewModel class, but this throws up an error.

I guess the way I have declared LiveData variables is not really the best. All I wanted was to access static data of temperature variables (a list of 6. But MutableLiveData<List<Int>> wasn't really working out.

Please also suggest how else can I make my ViewModel and WebSocket talk to each other.

Thanks in advance.

Answer 1

problem :

you have two big mistakes

1-declare web web Socket in activity or fragment

2-use activity in its view model

explain concept:

1-you have to declare separated class to web socket implement (create instance ,listen ,invoke,connect and disconnect) to apply single responsibility principle

2-In MVVM the relation between view and view model is one direction view observe observable inside view model and but view model has no reference to view unlike MVP relation be 2 direction so you shouldn't declare your main activity in side view model

Solution:

1-socket class

class SocketService{
    companion object {val instance :SocketService}
    fun connect() 
    fun disconnect()
    fun sendMessage(invokeMethodName:String,data:JsonObject)
    fun subscribe(listenMethodName:String,listner:Listner)
    }

2-view model

  val receiveMessageResponse = MutableLiveData<String>()
      SocketService.instance!!.subscribe(RECEIVE_MESSAGE, HubEventListener {
                receiveMessageResponse.postValue(it)
            })

3-activity

viewModel.receiveMessageResponse.observe(this, Observer {
         //use the received message here
        })

Conclustion:

socketService ------> view model ----------> activity

activity <-------- viewmodel <------------- socketService