Help with JFrame

[Albert]

In the Paint method of a JFrame I can call a method like drawRect( ) and it will work. But when I try to call a class method for drawing, it won't work. It creates the window but doesn't draw anything in it. Here is a simple example. It uses a class, Design, that just uses drawRect and drawOval. An applet can use the Design class and its methods just fine. Why can't the JFrame do the same?

Code:

import java.awt.*;
import javax.swing.*;

public class DrawTest extends JFrame {

Design d;

public DrawTest( ) {
super( "Drawing Test" );

setSize(100, 100 );
setVisible( true );
}

public void init( ) {
d = new Design( );
}

public void paint( Graphics g ) {
super.paint( g );
d.draw( g );
}

public static void main( String args[] ) {
DrawTest application = new DrawTest( );
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
} // end of main

} // end of DrawTest

Thanks

Albert

[Felissa]

I am not sure if you could draw straight into a JFrame instance....though, I might be wrong.

I think most Java programmers use an instance of the Canvas class to draw on frames.

here is an example

Greetings

Felissa

[Eric]

What you want to paint on, is not the JFrame, but on its contentPane.

This is more or less the way I always do it, by using JPanels:

Code:

import javax.swing.JFrame;

class{
    main{
         //create JFrame
         JFrame frame = new JFrame ("A JFrame");
         frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        
         //create instance of drawing class
         //i guess you could do it on init()..
         Design d = new Design();
        
         //add contentPane to frame
         //add drawings to contentPane
         frame.getContentPane().add(d);
         frame.pack();
         frame.setVisible(true);

    }
}

Code:

import javax.swing.JPanel;

Design class extends JPanel{
    public Design(){ //constructor
         //add initial values
         ...
         //set panel color and size
         setBackground (Color.gray);
         setPreferredSize (new Dimension(600,600));
    }    

    ...stuff
    public void paint(Graphics g) {
        //drawings go here
        super.paint(g);
        ....stuff
    }
    ...stuff
}

Greetings

Eric