Beginner Java graphics problem

silver campaign

Hi, I am having some difficulty with Java. All I want to do is draw a square centered on a JFrame. I have to use a inner class by extending JPanel.

All this code displays is the JFrame with no shape?

package course1;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class GrowAndShrinkSquareGUI{
JFrame frame;

class SquareDrawPanel extends JPanel{

public void paintComponent(Graphics g){
g.setColor(Color.green);
g.fillRect(25,25,100,100);
}
} /* inner class ends */

public static void main (String[] args){
SimpleGUI test = new SimpleGUI();
test.go();
}

public void go(){
frame = new JFrame();
frame.setSize(500,500);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

}

silver campaign

I have tried this also, but it only displays a JFrame aswell.

package course1;
import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;
import javax.swing.JPanel;


public class test{
JFrame frame;

public class SquareDrawPanel extends JPanel {

private static final long serialVersionUID = 1L;
private int diameter = 100;

public void paintComponent(Graphics g) {

int width = this.getWidth();
int height = this.getHeight();

g.setColor(Color.WHITE);
g.fillRect(0, 0, width, height);

int x = (width - diameter) / 2;
int y = (height - diameter) / 2;

g.setColor(Color.GREEN); // J
g.fillRect(x, y, diameter, diameter);
} /* inner class ends */

}

public static void main (String[] args){
SimpleGUI test = new SimpleGUI();
test.go();
}

public void go(){
frame = new JFrame();
frame.setSize(500,500);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

}

yes there

Think about the structure of swing and component placement. You are only missing one line. Also need to rethink the center coordinates.

silver campaign

Thanks, I;ll have a look in half an hour. think I need another cup of tea first!!

silver campaign

No Sorry folks. I'm still not getting it. Any more ideas?

Anesthetize

silver campaign wrote: »

No Sorry folks. I'm still not getting it. Any more ideas?

You've already declared a class for the square shape as an inner class. You now need to create an object of this class and add it to the JFrame.