DoItMission - 03 두 개의 이미지뷰에 이미지 번갈아 보여주기

1. MainActivity.java

-Button.setOnClickListener() 메서드 주의

package com.example.salgu.doitmission03answer;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    ImageView imageView01;
    ImageView imageView02;

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

        imageView01 = (ImageView)findViewById(R.id.imageView01);
        imageView02 = (ImageView)findViewById(R.id.imageView02);

        Button button01 = (Button)findViewById(R.id.button01);
        button01.setOnClickListener(new View.OnClickListener(){
            public void onClick(View v){
                moveImageUp();
            }
        });

        Button button02 = (Button)findViewById(R.id.button02);
        button02.setOnClickListener(new View.OnClickListener(){
            public void onClick(View v){
                moveImageDown();
            }
        });

        moveImageUp();
    }

    private void moveImageUp(){
        imageView01.setImageResource(R.drawable.beach);
        imageView02.setImageResource(0);

        imageView01.invalidate();
        imageView02.invalidate();
    }

    private void moveImageDown(){
        imageView01.setImageResource(0);
        imageView02.setImageResource(R.drawable.beach);

        imageView01.invalidate();
        imageView02.invalidate();
    }
}