[Kotlin] Handler

UI 작업은 Main Thread에서 해야 하는데 만약 Worker Thread에서 UI 변경을 해야 한다면 Handler를 이용하여 Main Thread와 연결해 주어야 한다. 단, Handler는 Main Thread에서 생성이 되어야 한다.

---

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"
    android:layout_gravity="center"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tvText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Ready"
        android:textSize="30dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/btnStart"
        android:layout_width="200dp"
        android:layout_height="100dp"
        android:text="start"
        android:textSize="16dp"
        android:layout_marginTop="30dp"
        app:layout_constraintTop_toBottomOf="@+id/tvText"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"/>

    <Button
        android:id="@+id/btnStop"
        android:layout_width="200dp"
        android:layout_height="100dp"
        android:text="Stop"
        android:textSize="16dp"
        app:layout_constraintTop_toBottomOf="@+id/btnStart"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml

 

 

 

 

 

 

MainActivity.kt

package com.jwsoft.kotlinproject

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Handler
import android.os.Message
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private var myThread: MyThread? = null
    lateinit var myHandler: MyHandler

    val SEND_START = 0
    val SEND_STOP = 1

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

        myHandler = MyHandler()

        btnStart.setOnClickListener {
            if (myThread != null) {
                myThread!!.stopThread()
            }
            myThread = MyThread()
            myThread!!.start()
        }

        btnStop.setOnClickListener {
            myHandler.sendEmptyMessage(SEND_STOP)
        }

    }

    inner class MyThread : Thread() {
        var i = 0
        var stopped = false

        fun stopThread() {
            stopped = true
        }

        override fun run() {
            super.run()

            while (!stopped) {
                var message: Message = Message.obtain()
                message.what = SEND_START
                message.arg1 = i++
                message.obj = " 초 경과"
                myHandler.sendMessage(message)

                sleep(100)
            }
        }
    }

    inner class MyHandler : Handler() {
        override fun handleMessage(msg: Message) {
            super.handleMessage(msg)

            when (msg.what) {
                SEND_START -> {
                    tvText.text = msg.arg1.toString() + msg.obj
                }
                SEND_STOP -> {
                    myThread?.stopThread()
                    tvText.text = "Stop"
                }
                else -> {

                }
            }
        }
    }

}

실행 결과

 

 

 

 

 

 

참고.

brunch.co.kr/@mystoryg/84

안드로이드 Handler 알고 쓰자