안드로이드 Data Binding 설정

build.gradle

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
    id 'kotlin-kapt'
    id 'kotlin-android-extensions'
}

android {
    compileSdk 32

    buildFeatures{
        viewBinding true
        dataBinding true
    }


    defaultConfig {
        applicationId "com.ej.room_exam"
        minSdk 30
        targetSdk 32
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}


dependencies {
    def room_version = "2.4.3"
    def lifecycle_version = "2.6.0-alpha01"
    def activity_version = "1.5.0"


    // Kotlin
    implementation("androidx.activity:activity-ktx:$activity_version")

    // ViewModel
    implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version")
    // LiveData
    implementation("androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version")
    // Lifecycles only (without ViewModel or LiveData)
    implementation("androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version")

    implementation("androidx.room:room-runtime:$room_version")
    annotationProcessor("androidx.room:room-compiler:$room_version")

    // To use Kotlin annotation processing tool (kapt)
    kapt("androidx.room:room-compiler:$room_version")

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.5.0'
    implementation 'com.google.android.material:material:1.6.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'


    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

 

메인 액티비티

binding.viewModel은 activity_main.xml의 viewModel과 매핑된다.

package com.ej.room_exam

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.viewModels
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.get
import androidx.lifecycle.lifecycleScope
import androidx.room.Room
import com.ej.room_exam.databinding.ActivityMainBinding
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch

class MainActivity : AppCompatActivity() {
    val mainViewModel: MainViewModel by viewModels()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        binding.lifecycleOwner = this

        binding.viewModel = mainViewModel

    }
}

 

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>
        <variable
            name="viewModel"
            type="com.ej.room_exam.MainViewModel" />
    </data>
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <EditText
            android:id="@+id/todo_edit"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginEnd="8dp"
            android:ems="10"
            android:hint="할일"
            android:text="@={viewModel.newTodo}"
            android:inputType="textPersonName"
            app:layout_constraintEnd_toStartOf="@+id/add_button"
            app:layout_constraintHorizontal_bias="0.0"
            app:layout_constraintStart_toStartOf="parent"
            tools:layout_editor_absoluteY="20dp"
            tools:ignore="MissingConstraints" />

        <Button
            android:id="@+id/add_button"
            android:onClick="@{() -> viewModel.insert(viewModel.newTodo)}"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="8dp"
            android:text="저장"
            app:layout_constraintEnd_toEndOf="parent"
            tools:layout_editor_absoluteY="20dp"
            tools:ignore="MissingConstraints" />

        <TextView
            android:id="@+id/result_text"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_marginStart="16dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="16dp"
            android:layout_marginBottom="16dp"
            android:text="@{viewModel.todos.toString()}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/todo_edit" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

 

ViewModel

package com.ej.room_exam

import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import androidx.room.Room
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch

class MainViewModel(application: Application) : AndroidViewModel(application){
    private val db by lazy {  Room.databaseBuilder(
            application,
            AppDatabase::class.java, "database-name")
        .allowMainThreadQueries()
        .build() }
    var todos :LiveData<List<Todo>>
    var newTodo : String? = null
    init {
        todos = getAll()
    }


    fun getAll(): LiveData<List<Todo>> {
        return db.todoDao().getAll()
    }

    fun insert(todo: String) {
        viewModelScope.launch(Dispatchers.IO) {
            db.todoDao().insert(Todo(todo))
        }
    }
}