我正在尝试在Java Applet中开发2D RPG游戏.现在我有一个简单的椭圆形,玩家可以使用左,右,上和下移动,并且与小程序边界的碰撞会阻止它们.问题是,我想创造一个玩家可以移动的巨大世界(2000px乘2000x)的区域.但是,我希望他们一次只能看到600px到400x的屏幕.如果他们继续向前移动,我希望屏幕跟随他们,同样是向上,向下和向左.谁能告诉我怎么做？到目前为止,这是我的代码：

import java.awt.*;
import java.awt.event.KeyEvent;
import java.applet.Applet;
import java.awt.event.KeyListener;
import javax.swing.*;

public class Main extends Applet implements Runnable, KeyListener
{
    private Image dbImage;
    private Graphics dbg;
    Thread t1;
    int x = 0;
    int y = 0;
    int prevX = x;
    int prevY = y;
    int radius = 40;
    boolean keyReleased = false;

    public void init()
    {
        setSize(600, 400);

    }

    public void start()
    {

        addKeyListener(this);
        t1 = new Thread(this);
        t1.start();
    }

    public void destroy()
    {
    }

    public void stop()
    {
    }

    public void paint(Graphics g)
    {
        //player
        g.setColor(Color.RED);
        g.fillOval(x, y, radius, radius);
    }

    public void update(Graphics g)
    {

        dbImage = createImage (this.getSize().width, this.getSize().height);
        dbg = dbImage.getGraphics();
        // initialize buffer
        if (dbImage == null)
        {
        }

        // clear screen in background
        dbg.setColor(getBackground());
        dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);

        // draw elements in background
        dbg.setColor(getForeground());
        paint(dbg);
        // draw image on the screen
        g.drawImage(dbImage, 0, 0, this);
    }

    @Override
    public void run()
    {
        while (true)
        {
            //x++;
            repaint();

            try
            {
                t1.sleep(17);
            }
            catch (Exception e)
            {
            }
        }
    }

    public boolean CheckCollision(String dir)
    {
        if (x <= 0 && dir.equals("L"))
        {
            x = prevX;
            return true;
        }
        else if (y <= 0 && dir.equals("U"))
        {
            y = prevY;
            return true;
        }
        else if (x >= (getWidth() - radius) && dir.equals("R"))
        {
            System.out.println(getWidth());
            x = prevX;
            return true;
        }
        else if (y >= (getHeight() - radius) && dir.equals("D"))
        {
            y = prevY;
            return true;
        }
        return false;
    }

    @Override
    public void keyPressed(KeyEvent e)
    {
        switch (e.getKeyCode())
        {
        case KeyEvent.VK_RIGHT:
            if (!CheckCollision("R"))
            {
            x += 4;
            prevX = x;
            }
            break;
        case KeyEvent.VK_LEFT:
            if (!CheckCollision("L"))
            {
            x -= 4;
            prevX = x;
            }
            break;
        case KeyEvent.VK_UP:
            if (!CheckCollision("U"))
            {
            y -= 4;
            prevY = y;
            }
            break;
        case KeyEvent.VK_DOWN:
            if (!CheckCollision("D"))
            {
            y += 4;
            prevY = y;
            }
            break;
        }

    }

    @Override
    public void keyReleased(KeyEvent arg0)
    {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyTyped(KeyEvent arg0)
    {
        // TODO Auto-generated method stub

    }
}