package com.learn.event_;
import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
/**
 * @author 咕咕貓
 * @version 1.0
 * 演示小球通過鍵盤控制上下左右的移動(dòng)→Java的事件控制
 */
public class BallMove extends JFrame{ //窗口
    MyPanel mp = null;
    public static void main(String[] args) {
        BallMove ballMove = new BallMove();
    }
    //構(gòu)造器
    public BallMove(){
        mp = new MyPanel();
        this.add(mp);
        this.setSize(400,300);
        //窗口JFrame對(duì)象可以監(jiān)聽鍵盤事件，即可以監(jiān)聽到面板上發(fā)生的鍵盤事件
        this.addKeyListener(mp);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }
}
//面板，可以畫出小球
//KeyListener是監(jiān)聽器，可以監(jiān)聽鍵盤事件
class MyPanel extends JPanel implements KeyListener {
    //為了讓小球移動(dòng)，把它的左上角的坐標(biāo)(x,y)設(shè)置成變量
    int x = 10;
    int y = 10;
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        g.fillOval(x, y,20,20); //默認(rèn)黑色
    }
    //有字符輸出時(shí)，該方法就會(huì)被觸發(fā)
    @Override
    public void keyTyped(KeyEvent e) {
    }
    //當(dāng)某個(gè)鍵按下時(shí)，該方法被觸發(fā)
    @Override
    public void keyPressed(KeyEvent e) {
        //System.out.println((char)e.getKeyCode() + "被按下...");
        //根據(jù)用戶按下的不同鍵，來處理小球的移動(dòng)(上下左右)
        //在java中，會(huì)給每一個(gè)鍵分配一個(gè)值(int類型)
        if(e.getKeyCode() == KeyEvent.VK_DOWN){ //KeyEvent.VK_DOWN就是向下的箭頭對(duì)應(yīng)code值
            y+=2;
        }else if(e.getKeyCode() == KeyEvent.VK_UP){
            y-=2;
        }else if(e.getKeyCode() == KeyEvent.VK_LEFT){
            x-=2;
        }else if(e.getKeyCode() == KeyEvent.VK_RIGHT){
            x+=2;
        }
        //讓面板重繪
        this.repaint();
    }
    //當(dāng)某個(gè)鍵釋放(松開)時(shí)，該方法被觸發(fā)
    @Override
    public void keyReleased(KeyEvent e) {
    }
}