android MVVM without Databinding

Question

Question : Can I implement android app with MVVM without using Databinding.

Problem I am trying to solve is pretty simple: read a list of items from backend API and show them in a Recylerview.

How I am implementing:

In the View - I have Activity and RecyclerViewAdapter Model : ApiResponse and data models network - retrofit API service, RxJava2

for ViewModel part - I have a ViewModel class(that doesn't derive from anything) that basically calls Retrofit Service and gets data using RxJava calls.

ViewModel has calls such as :

 void getItems();
 void addItemData();
 void removeItem();

which call service with RXJava2 as

 ObServable<ApiResponse> getItems();
 ObServable<ApiResponse> addItemData();
 ObServable<ApiResponse> removeItem();  

View instantiates ViewModel object. ViewModel gets the instance of Adapter object during creation. In the View, clicking a button calls a ClickHandler in the Activity which calls a ViewModel#getItems() method. Since ViewModel has link to Adapter, the viewModel updates the items in the adapter so that RecyclerView is automatically updated.

I am not sure if this is right approach for MVVM.

Databinding seems a bit like spaghetti to me.

Again, can we implement MVVM in android without DataBinding ? Is the approach OK?

Answer 1

Yes! You can. But i think your approach can be better. Remember that the view model must not have a reference to your view. ViewModel expose observables, and in your view, you should observe those observables and react over changes. You can have something like this:

Note: This example is with Kotlin and LiveData because, why not? But you can take this and use it with Java & Rx

ItemsViewModel : ViewModel() {
  private val items = MutableLiveData<List<Items>>()

  fun getAllItems() : LiveData<List<Items>> {
      return items
    }

   //..
}

ItemsActivity : Activity() {
  private var itemsAdapter: ItemsAdapter? = null
  private var viewModel: ItemsViewModel? = null

  override fun onCreate(savedInstance: Bundle) {
  // ...

   // Create your Adapter
   itemsAdapter = ItemsAdapter()
   recyclerView.adapter = itemsAdapter

   // Create and observe your view model
   viewModel =  ViewModelProviders.of(this).get(ItemsViewModel::class.java)

   viewModel.getAllItems().observe(this, Observer {
      it?.let {
          adapter?.datasource = it
      }
}

In this case, the view observes view model, and notify the adapter. Then in your adapter, you do the bind as usual, without databinding.