Filterable RecyclerView for Android

1 Filter Recycler View.md

DEPENDENCIES

• implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
• implementation "io.reactivex.rxjava2:rxjava:2.1.9"
• implementation "io.reactivex.rxjava2:rxkotlin:2.2.0"
• implementation 'com.jakewharton.rxbinding2:rxbinding-kotlin:2.1.1'
• implementation "android.arch.lifecycle:extensions:1.1.1"

Process Flow

ViewModel --> Business Logic (Initiate Model, listen to changes on textViews, and filter) -> Callback to Activity to refresh recycleView

Credits to

• https://github.com/2hamed/FilterableRecyclerViewTutorial
• https://android.jlelse.eu/filterable-recyclerview-in-android-the-how-to-a9ade9cd26

2Model.kt

data class User(
  val id: Int,
  val name: String,
  val age: Int)

3SimpleAdapter.kt

class SimpleRecyclerAdapter(private val context: Context, private val users: List<User>) : RecyclerView.Adapter<SimpleRecyclerAdapter.UserHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserHolder {
      //Declare the layout Resources
        return UserHolder(LayoutInflater.from(context).inflate(R.layout.rcl_item_post, parent, false))
    }

    override fun getItemCount() = users.size

    override fun onBindViewHolder(holder: PostHolder, position: Int) {
        holder.bind(users[position])
    }

    class UserHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun bind(user: User) {
          //Bind layout
            itemView.NameView.text = user.name
            itemView.AgeView.text = user.age
        }
    }
}

4UserViewModel.kt

class ViewModel: UserViewModel(){
  //This remains unchanged
  private val originalList = listof(
    User(1, Addam, 30),
    User(2, Herpderp, 20)
  )
  //This will change often as user inputs
  val filteredUsers: MutableList<User> = mutableListOf()
  
  //This will be passed to the Adapter after filtering
  val oldUsers: MutableList<User> = mutableListOf()
  
  init{
    oldUsers.addAll(originalList)
  }
  
  //bind the Textview to this function for onTextChanged
fun search(query: String): Completable = Completable.create {
        val wanted = originalList.filter {
            it.name.contains(query) || it.age.contains(query)
        }.toList()

        filteredUsers.clear()
        filteredUsers.addAll(wanted)
        it.onComplete()
    }
}

5UserDiffUtilCallback.kt

class UserDiffUtilCallback(private val oldList: List<User>, private val newList: List<User>) : DiffUtil.Callback() {
    override fun getOldListSize() = oldList.size

    override fun getNewListSize() = newList.size

    override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int) = oldList[oldItemPosition].id == newList[newItemPosition].id

    override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int) = true
}

6MainActivity.kt

class MainActivity : AppCompatActivity() {
  private lateinit var viewModel: UserViewModel
  private val disposable = CompositeDisposable()
  
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    
    viewModel = ViewModelProviders.of(this).get(UserViewModel::class.java)
    
    //Add the old users into the adapter to show all first
    recyclerView.layoutManager = LinearLayoutManager(this)
    recyclerView.adapter = SimpleRecyclerAdapter(this, viewModel.oldFilteredUsers)
    
    //Here is the business logic executor, actually can be placed into the viewmodel also can
    search_text_view
      .textChanges()
      .debounce(200, TimeUnit.MILLISECONDS)
      .subscribe{
        viewModel
          .search(it.toString())
          .subscribeOn(Schedulers.computation())
                            .observeOn(AndroidSchedulers.mainThread())
                            .subscribe {
                              //dispatch the different result from the callback into adapter
                              val diffResult = DiffUtil.calculateDiff(UserDiffUtilCallback(viewModel.oldFilteredPosts, viewModel.filteredPosts))
                              viewModel.oldFilteredPosts.clear()
                              viewModel.oldFilteredPosts.addAll(viewModel.filteredPosts)
                              diffResult.dispatchUpdatesTo(recyclerView.adapter)
                            }.addTo(disposable)
      }.addTo(disposable)
  }
  
  override fun onDestroy() {
        super.onDestroy()
        disposable.clear()
    }
}