Java游戏口吃

我刚刚开始开发一款2d侧滚平面射击游戏。几天来,我一直对飞机的运动有问题。出于某种原因,每隔一秒钟左右,精灵似乎就会结巴。这几乎就像它跳回了一帧什么的,然后从它停下来的地方继续。我一直没有找到导致这种情况的原因。有什么想法吗? 整个项目可以在这里找到: http://www.upload.ee/files/3975636/planes.zip.html

主要类别:

package planes;

import javax.swing.JFrame;

import planes.Entities.Player;

public class Game extends JFrame{

    private static final long serialVersionUID = 1L;
    private boolean isRunning = true;
    public static int fps = 60;

    private Frame frame;
    private InputHandler input;
    public static Player player;

    public static void main(String[] args) {
        Game game = new Game();
        game.run();
        System.exit(0);
    }

    public void update() {
        player.update();
    }

    public void draw() {
        frame.draw();
    }

    public void initialize() {

        Sprites.init();
        frame = new Frame();
        input = new InputHandler(frame);
        player = new Player(0, 0, Sprites.player, input);

    }

    public void run() {
        initialize();

        while (isRunning) {
            long time = System.currentTimeMillis();

            update();
            draw();
            time = (1000 / fps) - (System.currentTimeMillis() - time);

            if (time > 0) {
                try {
                    Thread.sleep(time);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

        }
        setVisible(false);
    }

}

框架类别:

package planes;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Insets;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.awt.image.ImageObserver;

import javax.swing.JFrame;

public class Frame extends JFrame{

    private Insets insets;
    private BufferedImage backBuffer;   

    Frame(){
        setTitle("Planes");
        setSize(Const.windowWidth, Const.windowHeight);
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setVisible(true);

        insets = getInsets();
        setSize(insets.left + Const.windowWidth + insets.right, insets.top
                + Const.windowHeight + insets.bottom);
        backBuffer = new BufferedImage(Const.windowWidth, Const.windowHeight,
                BufferedImage.TYPE_INT_RGB);
    }



    public void draw(){
        Graphics2D g = (Graphics2D) getGraphics();
        Graphics2D bbg = (Graphics2D) backBuffer.getGraphics();

        bbg.setColor(Color.WHITE);
        bbg.fillRect(0, 0, Const.windowWidth, Const.windowHeight);

        Game.player.draw(bbg);
        bbg.drawRect(32, 32, 32, 32);

        g.drawImage(backBuffer, insets.left, insets.top, this);
    }

}