Java applet不会渲染图像（png）

When I run the game, I only see black screen, no image.

当我运行游戏时,我只看到黑屏,没有图像。

I'm programming my game with the help of kilobolt game development guide: http://www.kilobolt.com/day-4-enter-the-robot.html

我在kilobolt游戏开发指南的帮助下编写我的游戏:http://www.kilobolt.com/day-4-enter-the-robot.html

I would really like to know what i did wrong.

我真的很想知道我做错了什么。

Player.java

package HideAndSeek;

import java.awt.*;
import java.awt.image.ImageObserver;

public class Player
{
    private Image image;
    private double velocity;
    private int x;
    private int y;

    public Player(Image image,double velocity,int x,int y)
    {
        this.image = image;
        this.velocity = velocity;
        this.x = x;
        this.y = y;
    }

    public void update(Graphics g,ImageObserver io)
    {
        g.drawImage(image, 0, 0, io);
    }
}

Game.java

package HideAndSeek;

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

public class Game extends Applet implements Runnable,KeyListener
{
    private Image background;
    private Graphics graphics;
    private java.net.URL base;
    private Player player;

    @Override
    public void init() 
    {
        background = createImage(this.getWidth(), this.getHeight());
        graphics = background.getGraphics();
        setSize(800, 480);
        setBackground(Color.BLACK);
        setFocusable(true);
        java.awt.Frame frame = (java.awt.Frame) this.getParent().getParent();
        frame.setTitle("Hide and Seek");
        base = getCodeBase();
        addKeyListener(this);
    }

    @Override
    public void start() 
    {
        player = new Player(getImage(base, "data/character.png"),1.0,0,0);
        Thread thread = new Thread(this);
        thread.start();
    }

    @Override
    public void stop() 
    {

    }

    @Override
    public void destroy() 
    {

    }

    public void update()
    {
        if (background == null) 
        {
            background = createImage(this.getWidth(), this.getHeight());
            graphics = background.getGraphics();
        }

        graphics.setColor(getBackground());
        graphics.fillRect(0, 0, getSize().width, getSize().height);
        graphics.setColor(getForeground());
        paint();
        graphics.drawImage(background, 0, 0, this);
    }

    public void paint()
    {
        player.update(graphics,this);
    }

    @Override
    public void run() 
    {
        while(true)
        {
            update();
            repaint();
            try
            {
                Thread.sleep(17);
            }
            catch(InterruptedException e)
            {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void keyPressed(KeyEvent arg0)
    {
        switch (arg0.getKeyCode())
        {
           case KeyEvent.VK_UP:
               System.out.println("You pressed up arrow");
               break;

           case KeyEvent.VK_DOWN:
               System.out.println("You pressed down arrow");
               break;

           case KeyEvent.VK_LEFT:
               System.out.println("You pressed left arrow");
               break;

           case KeyEvent.VK_RIGHT:
               System.out.println("You pressed right arrow");
               break;

           case KeyEvent.VK_SPACE:
               System.out.println("You pressed the space key");
               break;
        }
    }

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

    }

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

    }
}

1 个解决方案

#1

You're doing the painting wrong. The Graphics Object you use to paint things on the screen is different for every time paint is called. Besides that you have not overridden the paint method correctly, there is an argument missing. Just change the method to this, and it should work:

你做错了。每次调用绘制时,用于在屏幕上绘制内容的图形对象都是不同的。除此之外你还没有正确覆盖paint方法,缺少一个参数。只需将方法更改为此,它应该工作:

public void paint(Graphics g)
{
player.update(g, this);
}