버튼 yes, no

Java

package com.example.ryan.myapplication;

import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    private static final int DIALOG_YES_NO_MESSAGE=1;
    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button =(Button)findViewById(R.id.button);
    }

    //버튼 클릭했을 때 호출되는 메소드
    public void onButtonClicked(View view){
        showDialog(DIALOG_YES_NO_MESSAGE);
    }

    protected Dialog onCreateDialog(int id){
        switch (id){
            case DIALOG_YES_NO_MESSAGE:
               //객체생성
                AlertDialog.Builder builder = new AlertDialog.Builder(this);
               //대화상자속성
               builder.setTitle("종료학인대화상자")
                        .setMessage("애플리케이션을종료하시겠습니까")
                        .setCancelable(false)
                        //"back"버튼으로 다이러로그를 취소할 수 없다
                       .setNegativeButton("No", new DialogInterface.OnClickListener() {
                           @Override
                           public void onClick(DialogInterface dialogInterface, int which) {
                               dialogInterface.cancel();
                               //대화상자종료
                           }
                       })
                       .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialogInterface, int which) {
                                MainActivity.this.finish();
                           //액티비티종료
                            }
                        });
               //
                AlertDialog alert =builder.create();
                return alert;
        }
        return null;
    }
}

xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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="com.example.ryan.myapplication.MainActivity"
    tools:layout_editor_absoluteY="81dp">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="22dp"
        android:layout_marginTop="30dp"
        android:onClick="onButtonClicked"
        android:text="대화상자생성" />
</RelativeLayout>