Calling the paint() method from another class?

Question

I am trying to call the paint() method from another class, but it just doesn't work.

Here is the code:

Main.java:

public class Main extends JFrame {
    private static final long serialVersionUID = 1L;

    private int WIDTH = 600;
    private int HEIGHT = 400;
    private String NAME = "Dark Ages";
    private String VERSION = "0.0.1 Pre-Alpha";
    static boolean running = false;

    private Image dbImage;
    private Graphics dbg;

    public Main() {
        //Initialize window
        JFrame frame = new JFrame();
        frame.setTitle(NAME + " - " + VERSION);
        frame.setSize(WIDTH, HEIGHT);
        frame.setVisible(true);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);

        //Running
        running = true;
    }

    public void paint(Graphics g) {
        dbImage = createImage(getWidth(), getHeight());
        dbg = dbImage.getGraphics();
        paintComponent(dbg);
        g.drawImage(dbImage, 0, 0, this);
    }

    public void paintComponent(Graphics g) {
        // Draw Images
        repaint();
    }

    public static void main(String args[]) {
        new Main();
        Player player = new Player();
    }
}

Player.java:

public class Player {

    public void paint(Graphics g) {
        g.drawRect(100, 100, 100, 100);
    }

}

Solution

How do I call the paint() method from another class in java?

In brief, you don't. And in fact, you shouldn't call it directly from the same class either. Instead you should change the state of the class (change its fields), and then call repaint() on it, which will suggest to the JVM that the component should be painted.

Other issues and suggestions:

• An obvious issue I see immediately in your code is that your class has a Graphics field, something that is dangerous to do. I suggest that you get rid of that field so that you're not tempted to use it.
• Do not draw directly within a JFrame, JDialog or other top-level window. These windows have too many roles to play behind the scenes that you don't really want to mess with how they render themselves or their children (unless you really know what you're doing and have definite need).
• Better to draw in the paintComponent(...) method override of a JPanel or other JComponents.
• In your paintComponent(...) override, don't forget to call the super's method: super.paintComponent(g);. This will allow Swing to do housekeeping drawing, such as erasing old out of date or deleted images, before you do your drawing.
• Run, don't walk to your nearest Swing painting tutorial.
• Your current Player class extends no Swing component and is added to no top level window, so its code will do nothing useful. Again, read the tutorials.
• Never call repaint() from within paint(...) or paintComponent(...).
• Please post modified code if possible.: please don't ask us to create code for you as that's your job. Please understand that the more code you create, the better a coder you'll be, and because of this, most of us don't feel that we should cheat you out of the opportunity to create your own code.

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Useful Java Tutorials:

• The Really Big Index: The main tutorial where you should start.
• Using Swing Components: How to create Swing GUI's
• Lesson: Performing Custom Painting: Introductory tutorial to Swing graphics
• Painting in AWT and Swing: Advanced tutorial on Swing graphics