今日內容：2D animations、Anonymous Inner Class

2D animations

學習如何用昨天學到的2D graphics功能以及簡單的判斷進行動態的畫面變化

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class MyPanel extends JPanel implements ActionListener{
    static final int PANEL_WIDTH = 500;
    static final int PANEL_HEIGHT = 500;
    Image enemy;
    Image backgroundImage;
    Timer timer;
    int xVelocity = 1;
    int yVelocity = 1;
    int x = 0;
    int y = 0;

    MyPanel() {
        this.setPreferredSize(new Dimension(500, 500));
        this.setBackground(Color.lightGray); // if backgroundImage not available
        enemy = new ImageIcon("ironman.png").getImage();
        backgroundImage = new ImageIcon("background.png").getImage();
        timer = new Timer(10, this); // 每10毫秒執行actionPerformed動作
        timer.start();
    }

    public void paint(Graphics g){
        super.paint(g); // 進行預設的繪製動作

        Graphics2D g2d = (Graphics2D) g;
        g2d.drawImage(backgroundImage, 0, 0, null);
        g2d.drawImage(enemy, x, y, null);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if(x >= PANEL_WIDTH-enemy.getWidth(null) || x < 0){
            xVelocity *= -1;
        }
        if(y >= PANEL_HEIGHT-enemy.getHeight(null) || y < 0){
            yVelocity *= -1;
        }
        x += xVelocity;
        y += yVelocity;
        repaint(); // using repaint instead of calling paint
    }
}

Anonymous Inner Class

在class中建立無名的inner class，用於action listener的效果很好

public class Greeting {
    public void Welcome(){
        System.out.println("Hello World!");
    }
}


public class Main {
    public static void main(String[] args){
        Greeting greeting = new Greeting();
        Greeting greeting2 = new Greeting(){
            @Override
            public void Welcome(){
                System.out.println("Yo Bro!");
            }
        };
        greeting.Welcome();
        greeting2.Welcome();
    }
}

接下來是實作練習
設置三個不同的按鈕，各自有不同的功能
不再implements ActionListener，而是在addActionListener中獨立創建

import javax.swing.JFrame;
import javax.swing.JButton;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MyFrame extends JFrame{
    JButton button1 = new JButton("Button #1");
    JButton button2 = new JButton("Button #2");
    JButton button3 = new JButton("Button #3");
    MyFrame(){
        button1.setBounds(100, 100, 100, 100);
        button2.setBounds(200, 100, 100, 100);
        button3.setBounds(300, 100, 100, 100);
        button1.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("You Pressed Button #1");
            }
        });
        button2.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e){
                System.out.println("You Pressed Button #2");
            }
        });
        button3.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e){
                System.out.println("You Pressed Button #3");
            }
        });

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(500, 500);
        this.add(button1);
        this.add(button2);
        this.add(button3);

        this.setLayout(null);
        this.setVisible(true);
    }
}

結語

今天是學習Java GUI的最後一天，明天就要正式進入開發遊戲的階段了，我目前的想法是將目標分為開發與優化兩個部分，開發大約可以花三天完成，而優化則是依據完成後缺什麼就新增什麼，不會讓自己有時間壓力。
今天也是快樂學習的一天，明天繼續！