[Kotlin] viewModelScope + ViewModel

build.gradle (Module: app)

dependencies {
    // viewModelScope
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0'

    // Coroutine
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.7'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.7'
}

 

 

 

 

 

 

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">

    <Button
        android:id="@+id/btnMain"
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:textAllCaps="false"
        android:text="Main -> Sub"
        android:textSize="24dp"
        android:layout_marginBottom="80dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/btnDownload"
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:textAllCaps="false"
        android:text="Download"
        android:textSize="24dp"
        app:layout_constraintTop_toBottomOf="@+id/btnMain"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml

 

 

 

 

 

 

activity_sub.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">

    <Button
        android:id="@+id/btnSub"
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:textAllCaps="false"
        android:text="Sub -> Main"
        android:textSize="24dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_sub.xml

 

 

 

 

 

 

MainActivity.kt

package com.jwsoft.kotlinproject

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.lifecycle.ViewModelProvider
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private lateinit var myViewModel: MyViewModel

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

        myViewModel = ViewModelProvider(
            this,
            ViewModelProvider.NewInstanceFactory()).get(MyViewModel::class.java
        )

        btnMain.setOnClickListener {
            startActivity(Intent(this, SubActivity::class.java))
            finish()
        }

        btnDownload.setOnClickListener {
            myViewModel.startDownload(applicationContext)
        }
    }

}

 

 

 

 

 

 

 

SubActivity.kt

package com.jwsoft.kotlinproject

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_sub.*

class SubActivity : AppCompatActivity() {

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

        btnSub.setOnClickListener {
            startActivity(Intent(this, MainActivity::class.java))
            finish()
        }
    }
    
}

 

 

 

 

 

 

 

MyViewModel.kt

package com.jwsoft.kotlinproject

import android.content.Context
import android.widget.Toast
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.*

class MyViewModel : ViewModel() {

    fun startDownload(context: Context) {
        viewModelScope.launch {
            repeat(100) {
                var percent = "메인화면에 필요한 데이터 받는 중... ${it+1}%"
                Toast.makeText(context, percent, Toast.LENGTH_SHORT).show()
                delay(2500)
            }
        }
    }

}

실행 결과

 

실행 결과

 

실행 결과