ViewModelAdapter

ViewModelAdapter is a project that apply MVVM pattern for RecyclerView.Adapter in Android.

Install

With setup of Jitpack first, than add dependency in your build.gradle

implementation 'com.github.carousell:ViewModelAdapter:0.2'

Concept

We want to make Activity/Fragment to be pure container and delegate the functionality to elements inside RecyclerView to fulfill clean and scaleable architecture. We use ViewModel as the data source of RecyclerView, and generate corresponding ViewHolder/View that will bind with the ViewModel and observe change or execute actions.

Usage & Example

• Create a list of ViewModels that extends ItemViewModel that represent the different items that will be displayed into the RecyclerView. The following methods should be implemented:

  • getKey: Provide a unique key to the ViewModel.
  • compare: Compare different ViewModel and return if they are identical.

  Example:

  class TextViewModel(private val item: TextItem) : ItemViewModel() {
  
      override fun getKey(): String {
          return item.key
      }
  
      override fun compare(viewModel: ItemViewModel): Boolean {
          if (viewModel is TextViewModel) {
              return viewModel.text == text
          }
          return false
      }
  }

• Create a list of ViewHolders that extends ViewModelHolder to interact with your corresponding ViewModel. The following methods should be implemented:

  • onBind: Subscribe to the data sources (LiveData, RxJava, etc) provided by your ViewModel.
  • onUnbind: Unsubscribe to the data sources (LiveData, RxJava, etc) provided by your ViewModel.

  Example:

  class TextHolder(itemView: View, private val lifecycleOwner: LifecycleOwner) :
      ViewModelHolder<TextViewModel>(itemView), Observer<String> {
  
      override fun onBind(viewModel: TextViewModel) {
          viewModel.liveData().observe(lifecycleOwner, this)
      }
  
      override fun onUnbind(viewModel: TextViewModel) {
          viewModel.liveData().removeObserver(this)
      }
  
      override fun onChanged(string: String?) {
          itemView.text.text = string
      }
  }

• Create adapter extends ViewModelAdapter which will handle the ViewModel binding for you. The only method need to implement:

  • onCreateViewHolder: Create the corresponding ItemViewModel via different modelType.

  Example:

    override fun onCreateViewHolder(
        parent: ViewGroup,
        modelType: Class<out ItemViewModel>
    ): ViewModelHolder<out ItemViewModel> {
        val layoutInflater = LayoutInflater.from(parent.context)
        return when (modelType) {
            TextViewModel::class.java -> TextHolder(
                layoutInflater.inflate(R.layout.adapter_text, parent, false),
                lifecycleOwner
            )
            EditViewModel::class.java -> EditHolder(
                layoutInflater.inflate(R.layout.adapter_edit, parent, false)
            )
            else -> throw RuntimeException("Not support")
        }
    }

Go to ./app module for more information.

Contributing

Thank you for being interested in contributing to this project. Check out the CONTRIBUTING document for more info.

About

ViewModelAdapter is created and maintained by Carousell. Help us improve this project! We'd love the feedback from you.

We're hiring! Find out more at http://careers.carousell.com/

License

ViewModelAdapter is released under Apache License 2.0. See LICENSE for more details.