import java.awt.*;
import java.awt.event.*;

public class TankClient extends Frame {
	
	public static final int GAME_WIDTH=800;
	public static final int GAME_HEIGHT=600;
	
    Tank myTank =new Tank(50,50);
	
	Image offScreenImage = null;
	
	public void paint(Graphics g) {

		myTank.draw(g);//理解一下面向对象
	}
	
	public void update(Graphics g) {
		if(offScreenImage == null) {
			offScreenImage = this.createImage(GAME_WIDTH, GAME_WIDTH);
		}
		Graphics gOffScreen = offScreenImage.getGraphics();
		Color c = gOffScreen.getColor();
		gOffScreen.setColor(Color.GREEN);
		gOffScreen.fillRect(0, 0, GAME_WIDTH, GAME_WIDTH);
		gOffScreen.setColor(c);
		paint(gOffScreen);
		g.drawImage(offScreenImage, 0, 0, null);
	}

	public void lauchFrame() {
		this.setLocation(400, 300);
		this.setSize(GAME_WIDTH, GAME_WIDTH);
		this.setTitle("TankWar");
		this.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		this.setResizable(false);
		this.setBackground(Color.GREEN);
		
		this.addKeyListener(new KeyMonitor());
		
		setVisible(true);		
		new Thread(new PaintThread()).start();
	}

	public static void main(String[] args) {
		TankClient tc = new TankClient();
		tc.lauchFrame();
	}
	
	private class PaintThread implements Runnable {

		public void run() {
			while(true) {
				repaint();
				try {
					Thread.sleep(50);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}
	}

	private class KeyMonitor  extends KeyAdapter
	{

		public void keyPressed(KeyEvent e) {

			System.out.println("ok");
			
            myTank.keyPressed(e);
		}
		
	}

}





import java.awt.*;
import java.awt.event.*;
public class Tank {

public static final int XSPEED =5;
public static final int YSPEED =5;

private	int x,y;
private boolean bL=false,bU=false,bR=false,bD=false;

enum Direction{L,LU,U,RU,R,RD,D,LD,STOP};
private Direction dir=Direction.STOP;	
	
	
	public Tank(int x, int y) {
		this.x = x;
		this.y = y;
	}

	public void draw(Graphics g)
	{
		Color c = g.getColor();
		g.setColor(Color.RED);
		g.fillOval(x, y, 30, 30);
		g.setColor(c);
			
		move();
	}
	
	void move()
	{
		switch(dir) {
		case L:
			x -= XSPEED;
			break;
		case LU:
			x -= XSPEED;
			y -= YSPEED;
			break;
		case U:
			y -= YSPEED;
			break;
		case RU:
			x += XSPEED;
			y -= YSPEED;
			break;
		case R:
			x += XSPEED;
			break;
		case RD:
			x += XSPEED;
			y += YSPEED;
			break;
		case D:
			y += YSPEED;
			break;
		case LD:
			x -= XSPEED;
			y += YSPEED;
			break;
		case STOP:
			break;
		}
	}
	
	
	public void keyPressed(KeyEvent e)
	{

		int key=e.getKeyCode();
//		if(key==KeyEvent.VK_RIGHT)
//		{
//			x +=5;
//		}
		
		switch(key)
		{
		case KeyEvent.VK_LEFT:
			bL=true;
			break;
		case KeyEvent.VK_UP:
			bU=true;
			break;
		case KeyEvent.VK_RIGHT:
			bR=true;
			break;
		case KeyEvent.VK_DOWN:
		    bD=true;
		    break;
		}
		locateDirection() ;
	}


	void locateDirection() 
	{
		if(bL && !bU && !bR && !bD) dir = Direction.L;
		else if(bL && bU && !bR && !bD) dir = Direction.LU;
		else if(!bL && bU && !bR && !bD) dir = Direction.U;
		else if(!bL && bU && bR && !bD) dir = Direction.RU;
		else if(!bL && !bU && bR && !bD) dir = Direction.R;
		else if(!bL && !bU && bR && bD) dir = Direction.RD;
		else if(!bL && !bU && !bR && bD) dir = Direction.D;
		else if(bL && !bU && !bR && bD) dir = Direction.LD;
		else if(!bL && !bU && !bR && !bD) dir = Direction.STOP;
	}
	

}