Android ListAdapter

 ListAdapter에 대해서 간단하게 보고 가겠습니다.

 

 RecyclerView를 사용할 때 데이터를 바꿔줄 때가 있습니다. 그럴 때 마다 notifyDataSetChanged() 를 호출하여 전체 데이터를 고치는데 diffUtil을 이용하여 변경된 데이터만 바꿔주며 아래와 같은 시간절약 효과가 있습니다.

 

 

MainActivity.kt

 

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val recyclerView = findViewById<RecyclerView>(R.id.programmingList)
        val adapter = ProgrammingAdapter()

        val p1 = ProgrammingItem(1,"J", "java")
        val p2 = ProgrammingItem(2,"K", "Kotlin")
        val p3 = ProgrammingItem(3,"A", "Android")

        adapter.submitList(listOf(p1,p2,p3))

        recyclerView.layoutManager = LinearLayoutManager(this)
        recyclerView.setHasFixedSize(true)
        recyclerView.adapter = adapter

        Handler(Looper.getMainLooper()).postDelayed(Runnable {

            val p3 = ProgrammingItem(3,"A", "Android")
            val p4 = ProgrammingItem(4,"C", "C")
            val p5 = ProgrammingItem(5,"V", "V")
            val p6 = ProgrammingItem(6,"B", "B")

            adapter.submitList(listOf(p3,p4,p5,p6))

        }, 4000)
        
    }

}

 

ProgrammingAdapater.kt

 

class ProgrammingAdapter : ListAdapter<ProgrammingItem, ProgrammingAdapter.ProgrammingViewHolder>(DiffUtil()) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ProgrammingViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.item_view, parent, false)
        return ProgrammingViewHolder(view)
    }

    override fun onBindViewHolder(holder: ProgrammingViewHolder, position: Int) {
        val item = getItem(position)
        holder.bind(item)
    }

    class ProgrammingViewHolder(view : View) : RecyclerView.ViewHolder(view) {
        val name = view.findViewById<TextView>(R.id.name)
        val initial = view.findViewById<TextView>(R.id.initial)

        fun bind(item : ProgrammingItem) {
            name.text = item.name
            initial.text = item.initial
        }
    }

    class DiffUtil : androidx.recyclerview.widget.DiffUtil.ItemCallback<ProgrammingItem>(){
        override fun areItemsTheSame(oldItem: ProgrammingItem, newItem: ProgrammingItem): Boolean {
            return oldItem.id == newItem.id
        }


        @SuppressLint("DiffUtilEquals")
        override fun areContentsTheSame(
            oldItem: ProgrammingItem,
            newItem: ProgrammingItem,
        ): Boolean {
            return oldItem == newItem
        }

    }



}

 

ProgrammingItem.kt

 

class ProgrammingItem(val id : Int, val initial : String, val name : String)

 

activity_main.xml

 

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/programmingList"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

 

item_view.xml

 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/initial"
        android:layout_width="42dp"
        android:layout_height="42dp"
        android:text="j"
        android:background="@drawable/item_red"/>

    <TextView
        android:id="@+id/name"
        android:text="java"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

 

item_red.xml

 

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

    <corners android:radius="150dp"></corners>
    <solid android:color="#F44336"></solid>

</shape>

 

 

 

 

- 참조

 

https://developer.android.com/reference/androidx/recyclerview/widget/DiffUtil

DiffUtil  |  Android Developers

 

https://medium.com/geekculture/android-listadapter-a-better-implementation-for-the-recyclerview-1af1826a7d21

Android: ListAdapter, a Better Implementation for the RecyclerView

 

https://www.youtube.com/watch?v=QsilZEC-cOs&t=552s