class MainActivity

 

package org.androidtown.mythread;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private static final String TAG="MainActivity";

    TextView textView;
    RequestThead thead;
    ResponseHandler responseHandler ;

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

        textView=(TextView)findViewById(R.id.textView);
    }


    public void onButton1Clicked(View v){
        Log.d(TAG, "첫번째 버튼 클릭됨 : " );

        textView.setText("스레드 시작함");

        if(thead!=null){
            thead.interrupt();
            thead=null;
        }
        if(responseHandler!=null){
            responseHandler=null;
        }

        responseHandler=new ResponseHandler();
        thead =new RequestThead();
        thead.setDaemon(true);
        thead.start();

        Toast.makeText(getApplicationContext(), "스레드 시작됨", Toast.LENGTH_SHORT).show();
    }


    class RequestThead extends Thread{
        public void run(){
            for(int i=0; i<100; i++){
                println("#" + i + " : 호출됨 ");

                try{
                    Thread.sleep(500);
                }catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        public void println(String data){
            Log.d(TAG, data);

            //에러 발생
            //textView.setText(data);
            Message message=responseHandler.obtainMessage();
            //번들로 상요에 데이터 전달.
            Bundle bundle=new Bundle();
            bundle.putString("data", data);
            message.setData(bundle);

            responseHandler.sendMessage(message);
        }
    }


    class ResponseHandler extends Handler{

        //UI 에 접근할 수 있는 메소드
        @Override
        public void handleMessage(Message msg) {
            Bundle bundle=msg.getData();
            String data =bundle.getString("data");

            textView.setText(data);
        }
    }


    // 2. 두번째 핸들러 사용법
   /* private int secondNum;
    private boolean isThread=true;

    class NewThread extends Thread{

        @Override
        public void run() {
            while (isThread){
                secondNum++;
                Log.i(TAG, "secondNum in thread :" + secondNum);

                try {
                    Thread.sleep(500);
                }catch (Exception e){
                    e.printStackTrace();
                }

                Message msg =new Message();
                msg=Message.obtain();
                msg.what=0;
                msg.arg1=0;
                msg.arg2=0;
                msg.obj=null;
                handler.sendMessage(msg);
                handler.sendEmptyMessage(0);
            }
        }
    }

    Handler handler =new Handler(){
        @Override
        public void handleMessage(Message msg) {
            if(msg.what==0){
                textView.setText(secondNum);
            }
        }
    };
*/


}

 

 

R.layout.activity_main

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="org.androidtown.mythread.MainActivity">

    <Button
        android:text="스레드시작"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:id="@+id/button"
        android:onClick="onButton1Clicked"
        />

    <TextView
        android:text="결과출력"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="76dp"
        android:id="@+id/textView"
        android:textSize="30sp" />


</RelativeLayout>