[Java] 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.

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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">

    <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_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

    <Button
        android:id="@+id/btnStart"
        android:layout_width="180dp"
        android:layout_height="80dp"
        android:text="Start"
        android:textSize="16dp"
        android:layout_marginTop="20dp"
        app:layout_constraintTop_toBottomOf="@+id/tvText"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/btnStop"
        android:layout_width="180dp"
        android:layout_height="80dp"
        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.java

package com.jwsoft.javaproject;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    TextView tvText;
    Button btnStart;
    Button btnStop;

    MyThread myThread;
    MyHandler myHandler;

    public final static int SEND_START = 0;
    public final static int SEND_STOP = 1;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        myHandler = new MyHandler();

        tvText = findViewById(R.id.tvText);
        btnStart = findViewById(R.id.btnStart);
        btnStop = findViewById(R.id.btnStop);

        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (myThread != null) {
                    myThread.stopThread();
                }
                myThread = new MyThread();
                myThread.start();
            }
        });

        btnStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myHandler.sendEmptyMessage(SEND_STOP);
            }
        });

    }

    class MyThread extends Thread {
        int i = 0;
        Boolean stopped = false;

        public void stopThread() {
            stopped = true;
        }

        @Override
        public void run() {
            super.run();

            while (!stopped) {
                Message message = Message.obtain();
                message.what = 0;
                message.arg1 = i++;
                message.obj = " 초 경과";
                myHandler.sendMessage(message);

                try {
                    sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    class MyHandler extends Handler {
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);

            switch (msg.what) {
                case SEND_START:
                    tvText.setText(Integer.toString(msg.arg1) + msg.obj);
                    break;

                case SEND_STOP:
                    tvText.setText("Stop");
                    myThread.stopThread();
                    break;

                default:
                    break;
            }
        }
    }

}

실행 결과

 

 

 

 

 

 

참고.

brunch.co.kr/@mystoryg/84

안드로이드 Handler 알고 쓰자