import java.awt.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class TankClient6 extends Frame {
    int x = 50, y = 50;
    Image offScreenImage = null;
    public static final int GAME_WIDTH=800;
    public static final int GAME_HEIGHT=600;

    public void paint(Graphics g) {
        Color c = g.getColor();
        g.setColor(Color.RED);
        g.fillOval(x, y, 30, 30);
        g.setColor(c);
        y += 5;
    }

    public void launchFrame() {
        this.setLocation(300, 50);
        this.setSize(GAME_WIDTH, GAME_HEIGHT);
        this.setBackground(Color.green);
        this.setTitle("TankWar");
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        setResizable(false);
        setVisible(true);

        this.addKeyListener(new KeyMonitor());
        setVisible(true);
        new Thread(new PaintThread()).start();
    }
    private class KeyMonitor extends KeyAdapter {
        public void keyPressed(KeyEvent e) {
            int key = e.getKeyCode();
            switch (key) {
                case KeyEvent.VK_LEFT:
                    x -= 5;
                    break;
                case KeyEvent.VK_UP:
                    y -= 5;
                    break;
                case KeyEvent.VK_RIGHT:
                    x += 5;
                    break;
                case KeyEvent.VK_DOWN:
                    y += 5;
                    break;
            }
        }
    }

    private class PaintThread implements Runnable {
        //内部类 （可以方便的访问包装类的方法。不方便公开的，只为包装类服务的类应当定义为内部类）
        @Override
        public void run() {
            while (true) {
                repaint();//会自动调用update方法
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public  void update(Graphics g){
        if(offScreenImage==null){
            offScreenImage=this.createImage(GAME_WIDTH,GAME_HEIGHT);
        }//拿到这个图片的颜色
        Graphics gOffScreen=offScreenImage.getGraphics();
        Color c=gOffScreen.getColor();
        gOffScreen.setColor(Color.green);
        gOffScreen.fillRect(0,0,GAME_WIDTH,GAME_HEIGHT);
        gOffScreen.setColor(c);
        print(gOffScreen);
        g.drawImage(offScreenImage,0,0,null);
    }

    public static void main(String[] args) {
        TankClient6 tankClient6=new TankClient6();
        tankClient6.launchFrame();
    }

}