Graphics drawing problem

From:

"sydpolen" <sydpolen@THRWHITE.remove-dii-this>

Newsgroups:

comp.lang.java.gui

Date:

Wed, 27 Apr 2011 15:35:37 GMT

Message-ID:

<1181840486.636009.196880@q19g2000prn.googlegroups.com>

  To: comp.lang.java.gui
Hi,

I'm a java gui newbie. I have this problem;

I made a class "Gui" I want to use as a template for future Gui
builds. I want to draw lines in the center. I made a "test" method
which I call from main class. For some reason the line I attempt to
draw is not visible. When I call sleep between the initiate() and the
test() methods the line will sometimes be visible.

I would appreciate any pointers of what I'm doing wrong. I paste the
source ...

import java.awt.*;
import javax.swing.*;
public class StartGui {
    public static void main(String[] args) throws Exception{
        Gui gui = new Gui();
        gui.initiate();
        //Thread.sleep(2000);
        gui.test(100,100,300,300);
    }
}

import javax.swing.*;
import java.awt.*;
public class Gui extends JFrame{

    Color cN = Color.LIGHT_GRAY;
    Color cW = Color.LIGHT_GRAY;
    Color cC = Color.LIGHT_GRAY;
    Color cE = Color.LIGHT_GRAY;
    Color cS = Color.LIGHT_GRAY;
    Color cGap = Color.BLACK;

    int widthW = 200;
    int widthC = 400;
    int widthE = 200;
    int heightN = 150;
    int heightC = 400;
    int heightS = 150;

    Graphics graphics;
    JPanel n;
    JPanel s;
    JPanel e;
    JPanel w;
    JPanel c;

    public Gui() {
        new JFrame("Gui");
        n = new JPanel();
        w = new JPanel();
        e = new JPanel();
        s = new JPanel();
        c = new JPanel();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }
    public void initiate() {
        getContentPane().setLayout(new BorderLayout(2,2));
        getContentPane().setBackground(cGap);
        n.setBackground(cN);
        n.setPreferredSize(new Dimension(widthE+widthC+widthW,heightN));
        w.setBackground(cW);
        w.setPreferredSize(new Dimension(widthW,heightC));
        c.setBackground(cC);
        c.setPreferredSize(new Dimension(widthC,heightC));
        e.setBackground(cE);
        e.setPreferredSize(new Dimension(widthE,heightC));
        s.setBackground(cS);
        s.setPreferredSize(new Dimension(widthE+widthC+widthW,heightS));
        getContentPane().add(e,BorderLayout.EAST);
        getContentPane().add(w,BorderLayout.WEST);
        getContentPane().add(n,BorderLayout.NORTH);
        getContentPane().add(s,BorderLayout.SOUTH);
        getContentPane().add(c,BorderLayout.CENTER);
        pack();
    }
    public void test(int x1, int y1, int x2, int y2){
        c.setBackground(Color.BLACK);
        graphics = c.getGraphics();
        graphics.setColor(Color.GREEN);
        graphics.drawLine(x1,y1,x2,x2);
    }
}

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