Data Binding

결과화면

 

파일구조

 

1. 빌드 환경
2. 레이아웃 및 바인딩 수식

 

 

1. 빌드 환경

    buildFeatures {
        dataBinding = true
    }

 

 

2. 레이아웃 및 바인딩 수식 

일반 레이아웃을 데이터 바인딩 레이아웃으로 변환하려면:
1. 레이아웃을 <layout>태그 로 감싸세요
2. 레이아웃 변수 추가(선택 사항)
3. 레이아웃 표현식 추가(선택 사항)
- 레이아웃 표현식은 @ 기호로 시작하고 중괄호 { }로 묶습니다.

 

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <data>

        <!-- 1. 일반적인 바인딩-->
        <variable
            name="firstName"
            type="String" />

        <variable
            name="lastName"
            type="String" />

        <!-- 2. data 바인딩-->
        <variable
            name="user"
            type="com.project.practice.User" />

        <!-- 3. ViewModel 바인딩-->
        <variable
            name="viewModel"
            type="com.project.practice.SimpleViewModel" />

        <!-- 4. RecyclerView 바인딩-->
        <variable
            name="mainAdapter"
            type="com.project.practice.MainAdapter" />

    </data>

    <androidx.appcompat.widget.LinearLayoutCompat
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:padding="10dp">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{firstName}"
            android:textSize="30sp"
            tools:text="홍" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{lastName}"
            android:textSize="30sp"
            tools:text="길동" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.firstName}"
            android:textSize="30sp"
            tools:text="홍" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.lastName}"
            android:textSize="30sp"
            tools:text="길동" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{viewModel.username}"
            android:textSize="30sp"
            tools:text="liveData 값" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text='@{"좋아요 수: " + (viewModel.likeCnt != null ? String.valueOf(viewModel.likeCnt) : "0")}'
            android:textSize="30sp" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="@{() -> viewModel.onLike()}"
            android:text="좋아요" />

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recyclerView_main"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:adapter="@{mainAdapter}"
            android:layout_marginTop="20dp" />

    </androidx.appcompat.widget.LinearLayoutCompat>

</layout>

 

 

MainActivity.kt

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

    private val viewModel: SimpleViewModel by viewModels()
    private lateinit var adapter: MainAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)

        // 1. 일반적인 바인딩
        binding.firstName = "홍"
        binding.lastName = "길동"

        // 2. data 바인딩
        binding.user = User("Hong", "Gil-dong")

        // 3. ViewModel 바인딩
        binding.lifecycleOwner = this
        binding.viewModel = viewModel
        viewModel.setUsername("이순신")

        // 4. RecyclerView 바인딩
        adapter = MainAdapter()
        binding.mainAdapter = adapter
        binding.recyclerViewMain.layoutManager = LinearLayoutManager(this)

        val items = List(20) { "${it + 1}번째 아이템" }
        adapter.submitList(items)
    }

}

 

 

User.kt

data class User(val firstName: String, val lastName: String)

 

 

SimpleViewModel.kt

class SimpleViewModel : ViewModel() {

    private val _username = MutableLiveData<String>()
    val username: LiveData<String> get() =  _username

    private val _likeCnt = MutableLiveData(0)
    val likeCnt: LiveData<Int> get() =  _likeCnt

    fun setUsername(name: String) {
        _username.value = name
    }

    fun onLike() {
        _likeCnt.value = _likeCnt.value?.plus(1) ?: 0
    }

}

 

MainAdapter.kt

class MainAdapter : ListAdapter<String, MainAdapter.ViewHolder>(diffUtil) {

    inner class ViewHolder(private val binding: ItemMainBinding) : RecyclerView.ViewHolder(binding.root) {
        fun bind(string: String) {
            // data binding 사용
            binding.itemText = string
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val binding = ItemMainBinding.inflate(LayoutInflater.from(parent.context), parent, false)
        return ViewHolder(binding)
    }

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

    companion object {
        val diffUtil = object : DiffUtil.ItemCallback<String>() {
            override fun areItemsTheSame(oldItem: String, newItem: String): Boolean {
                return oldItem == newItem
            }

            override fun areContentsTheSame(oldItem: String, newItem: String): Boolean {
                return oldItem == newItem
            }

        }
    }

}

 

 

item_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <data>

        <variable
            name="itemText"
            type="String" />

    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:id="@+id/textView_main_item"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:textSize="30sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:text="@{itemText}"
            tools:text="1번째 아이템" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

 

---

 

참조

 

데이터 바인딩 라이브러리  |  Android Developers

 

Data Binding in Android  |  Android Developers