Example of MVVM Setup with viewmodel and viewmodelFactory

•  First of all add dependency
  

  val lifecycle_version = "2.7.0"

  implementation("androidx.lifecycle:lifecycle-livedata:$lifecycle_version")
  implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version")

  implementation ("com.squareup.retrofit2:retrofit:2.9.0")
  implementation ("com.squareup.retrofit2:converter-gson:2.9.0")

• after that create Retrofit file for setup Baseurl and connectivity.
  
  

  object RetrofitClient {
      private const val BASE_URL = "https://jsonplaceholder.typicode.com/"
  
      val retrofit: Retrofit by lazy {
          Retrofit.Builder()
              .baseUrl(BASE_URL)
              .addConverterFactory(GsonConverterFactory.create())
              .build()
      }
  
      val apiInterface: ApiInterface by lazy {
          retrofit.create(ApiInterface::class.java)
      }
  }
  

  
  
• After that make interface class
  

  interface ApiInterface {
      @GET("posts")
      suspend fun getPosts(): List<PostListResponseItem>
  }

  
  
  
• Create data model class according to your response
  

  data class PostListResponseItem(
      val body: String,
      val id: Int,
      val title: String,
      val userId: Int
  )

  
  
• Create Adapter class for set recyclerview
  
  

  class MainAdapter(private val list: ArrayList<PostListResponseItem>) :
      RecyclerView.Adapter<MainAdapter.ViewHolder>() {
  
      inner class ViewHolder(private val binding: ItemRowBinding) :
          RecyclerView.ViewHolder(binding.root) {
          fun bind(item: PostListResponseItem) {
              binding.textView.text = item.title
              binding.textView2.text = item.body
              binding.textView3.text = item.userId.toString()
              binding.textView4.text = item.id.toString()
          }
  
      }
  
      override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MainAdapter.ViewHolder {
          val laybinding = ItemRowBinding.inflate(LayoutInflater.from(parent.context), parent, false)
          return ViewHolder(laybinding)
      }
  
      override fun onBindViewHolder(holder: MainAdapter.ViewHolder, position: Int) {
          holder.bind(list[position])
      }
  
      override fun getItemCount(): Int {
          return list.size
      }
  
  }

  
  
  
• Create repository class
  

  class MainRepository(private val apiInterface: ApiInterface) {
  
      suspend fun getposts(): List<PostListResponseItem> {
          return apiInterface.getPosts()
      }
  }

  
  
  
  
  
• Create Viewmodel class
  

  class MainViewmodel(private val mainRepository: MainRepository) : ViewModel() {
      private var _postlist = MutableLiveData<List<PostListResponseItem>>()
      val postList: LiveData<List<PostListResponseItem>>
          get() = _postlist
  
      fun getPostList() {
          viewModelScope.launch(Dispatchers.IO) {
              try {
                  val result = mainRepository.getposts()
                  _postlist.postValue(result)
              } catch (e: Exception) {
              }
          }
      }
  }

  
  
  
  
  
• Create viewmodel factory for viewmodel
  
  

  class MainViewmodelFactory(private val repository: MainRepository) : ViewModelProvider.Factory {
      override fun <T : ViewModel> create(modelClass: Class<T>): T {
          if (modelClass.isAssignableFrom(MainViewmodel::class.java)) {
              return MainViewmodel(repository) as T
          }
          throw IllegalArgumentException("Unknown Exception from Viewmodel")
  
      }
  }

  
  
  
  
• Call viewmodel in MainActivity
  
  

  val repository = MainRepository(RetrofitClient.apiInterface)
  mainViewmodel =
      ViewModelProvider(this, MainViewmodelFactory(repository))[MainViewmodel::class.java]
  mainViewmodel.getPostList()
  mainViewmodel.postList.observe(this, Observer {
      binding.recyclerView.addItemDecoration(
          DividerItemDecoration(
              this,
              DividerItemDecoration.VERTICAL
          )
      )
      adapter = MainAdapter(it as ArrayList<PostListResponseItem>)
      binding.recyclerView.adapter = adapter
  })
  

  
  
  
  
  
• Note:- Make sure you have given the Internet Connection as well for call api from server