[JETPACK_Android View] ViewBinding

1 ViewBinding 특징

- Null 안전성 : 뷰의 직접 참조를 생성하지 않으므로 뷰 ID 부재에 의한 null 포인터 예외가 발생하지 않음

- 유형 안전성 : 각 바인딩 클래스에 있는 필드 유형이 XML 파일에서 참조하는 뷰와 일치하므로 클래스 변환 예외가 발생하지 않음

 

2 Activity

// build.gradle에 데이터 바인딩 추가 !
buildFeatures{
        viewBinding = true
    }

// activity_main.xml

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

        <TextView
            android:id="@+id/testText"
            android:textSize="50sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello World!"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

</LinearLayout>

// MainActivity.kt

class MainActivity : AppCompatActivity() {

    private lateinit var binding : ActivityMainBinding

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

        /* ViewBinding - Activity */
        binding = ActivityMainBinding.inflate(layoutInflater)
        val view = binding.root
        setContentView(view)
		
        /* 데이터 바인딩을 사용해 텍스트 값 변경 */
        binding.testText.text = "변경된 텍스트"

    }
}

 

2 Fragment

//activity_.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=".Activity">

    <FrameLayout
        android:id="@+id/frameArea"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

// Activity.kt
// 프레그먼트 사용을 위한 FragmentManager 세팅

class Activity : AppCompatActivity() {

    val manager = supportFragmentManager

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_)

        val transaction = manager.beginTransaction()
        val fragment = TestFragment()
        transaction.replace(R.id.frameArea, fragment)
        transaction.addToBackStack(null)
        transaction.commit()
    }
}

//TestFragment.xml

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

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:id="@+id/fragmentText"
        android:textSize="50sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="hello_blank_fragment" />

</FrameLayout>

// TestFragment.kt

class TestFragment : Fragment() {

	//dataBinding 설정
    private var _binding : FragmentTestBinding? = null
    private val binding get() = _binding!!

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

    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

		// DataBinding을 사용해 fragmentText의 text 변경 !
        
        _binding = FragmentTestBinding.inflate(inflater, container, false)
        val view = binding.root

        binding.fragmentText.text = "fragment Text"
        return view
    }

}