paintComponent没有画任何东西吗？

Question

I haven't been able to paint anything using an actionListener and paintComponent. I'm pretty sure I have the image name/path right. What am I doing wrong?

JApplet "Runner.java"

public class Runner extends JApplet{

    public void init(){
        World world = new World();
        Container screen = this.getContentPane();
        screen.add(world);
        setSize(1200, 800);
        repaint();
    }
}

part of "World.java"

protected ArrayList<WorldObject> allStillObjects = new ArrayList<WorldObject>();
protected ArrayList<MovableObject> allMovableObjects = new ArrayList<MovableObject>();
protected ArrayList<WorldObject> screenStillObjects = new ArrayList<WorldObject>();
protected ArrayList<MovableObject> screenMovableObjects = new ArrayList<MovableObject>();

public World(){
    this.setPreferredSize(new Dimension(SCREEN_WIDTH, SCREEN_HEIGHT));
    this.setBackground(new Color(255,255,255));
    this.setFocusable(true);
    this.setFocusTraversalKeysEnabled(false);

    this.addObject(new Card(this, "Two of Clubs", 0, 0, "card_two_c.png"));

    timer = new Timer(60, new ClickListener());
    timer.start();
}

public void addObject(WorldObject obj){
    if(obj instanceof MovableObject){
        this.allMovableObjects.add((MovableObject)obj);
        if(isOnScreen(obj))
            this.screenMovableObjects.add((MovableObject)obj);  
    }else{
        this.allStillObjects.add(obj);
        if(isOnScreen(obj))
            this.screenStillObjects.add(obj);
    }
}

public void paintComponent(Graphics g){
    super.paintComponent(g);
    for(WorldObject obj : this.screenStillObjects)
        obj.paintComponent(g);
    for(MovableObject obj : this.screenMovableObjects)
        obj.paintComponent(g);
}

private class ClickListener implements ActionListener{

    public void actionPerformed(ActionEvent e){    
         repaint();
    }
}

"ImageObject.java"

protected ImageIcon pic;

public ImageObject(World world, String name, int worldX, int worldY, String imageName){
    super(world, name, worldX, worldY);
    URL imgURL = getClass().getResource("images/" + imageName);
    pic = new ImageIcon(imgURL);

    this.width = pic.getIconWidth();
    this.height = pic.getIconHeight();
}

public void paintComponent(Graphics g){
    super.paintComponent(); //doesn't work with or without this line
    pic.paintIcon(world, g, this.getWorldX(), this.getWorldY());
}

If there isn't enough of the code here I can add more

Edit: What's the best alternative to using a JApplet? World extends JPanel, WorldObject extends JPanel, ImageObject extends WorldObject, MovableObject extends ImageObject, Card extends MovableObject

I added the method for addObject above.

Answer 1

Well thank you for your answers, er, comments! They were very helpful. I went and changed my program so that it used a JFrame instead of a JApplet, and after a little fiddling, got an image to print. From there I was able to revert back to a JApplet and it works! Still not sure what my initial problem was though :|