[Android] ViewModelFactory

ViewModelFactory는 ViewModel을 통해 전달되는 인자가 있을 때 사용됩니다

 

class MainActivityViewModel(
    startingTotal: Int
) : ViewModel() {
}

위와 같이 전달 인자가 있으면 사용해요

 

ViewModelFactory 실습

 

MainActivityViewModel

class MainActivityViewModel(
    startingTotal: Int
) : ViewModel() {
    private var total=0
    init {
        total = startingTotal
    }

    fun getTotal(): Int {
        return total
    }
    fun setTotal(input: Int) {
        total+=input
    }
}

 

MainActivityViewModelFactory

class MainActivityViewModelFactory(private val startingTotal: Int) : ViewModelProvider.Factory {
    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
        if (modelClass.isAssignableFrom(MainActivityViewModel::class.java)) {
            return MainActivityViewModel(startingTotal) as T
        }
        throw IllegalArgumentException("Unknown ViewModel Class")
    }
}

 

Factory에 ViewModel을 override 하기 1

Factory에 ViewModel을 override 하기 2

 

위와 같이 override를 하고 해당 코드와 같이 if문을 적은 후, 꼭 throw 보일러 코드를 적어주셔야 에러가 안납니다.

 

MainActivity

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    private lateinit var viewModel: MainActivityViewModel
    private lateinit var viewModelFactory: ManiActivityViewModelFactory

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

        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        viewModelFactory = MainActivityViewModelFactory(125)
        viewModel = ViewModelProvider(this, viewModelFactory).get(MainActivityViewModel::class.java)

        binding.resultTextView2.text = viewModel.getTotal().toString()
        binding.insertButton2.setOnClickListener {
            viewModel.setTotal(binding.inputEditText2.text.toString().toInt())
            binding.resultTextView2.text = viewModel.getTotal().toString()
        }
    }
}

viewModel에 대해서는 이전 블로그 포스팅이 있으니 설명은 생략하겠습니다!

viewModelFactory를 추가해 주시고 해당 viewModel에 인자를 넣어줍니다

 

이전 글 보기 : dduntorry.tistory.com/entry/Android-ViewModel

[Android] ViewModel

 

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">

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

        <EditText
            android:id="@+id/input_edit_text2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number"
            android:textSize="36sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.323"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.064" />

        <Button
            android:id="@+id/insert_button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="50dp"
            android:layout_marginTop="40dp"
            android:text="Add"
            android:textSize="36sp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/input_edit_text2" />

        <TextView
            android:id="@+id/result_text_view2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="45dp"
            android:layout_marginTop="32dp"
            android:layout_marginEnd="41dp"
            android:textSize="36sp"
            app:layout_constraintEnd_toEndOf="@+id/insert_button2"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/insert_button2" />

        <Button
            android:id="@+id/intent_button5"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="다음"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/input_edit_text2" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

 

xml 화면

 

이로써 ViewModelFactory 실습을 마치겠습니다