simple painting... really confusing...

[Jhedzkie Skies]

hi there. i am trying to do a gantt chart off java.awt.Graphics...

i found a very simple class for paint

  class GanttChart extends JPanel
    {
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);

            g.drawRect(10,10,70,30);
            g.drawRect(80,10,40,30);
            g.drawRect(120, 10, 80, 30);
        }
    }  

that is used with an applet...

  package os;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Graphics;

import javax.swing.JApplet;
import javax.swing.JPanel;

public class ganttcharts extends JApplet
{
    private Drawing drawing;

    public void init()
    {

        drawing = new Drawing();
        Container cont =  getContentPane();
        cont.setLayout(new BorderLayout());
        cont.add(drawing, BorderLayout.CENTER);
    }
    private static final class Drawing extends JPanel
    {
        public void paintComponent (Graphics g)
        {
            super.paintComponent(g);

            g.drawRect(10,10,70,30);
            g.drawRect(80,10,40,30);
            g.drawRect(120, 10, 80, 30);
        }
    }
}  

now, i am trying to do it inside a JFrame. but, i am really confused on how to do it.

  package os;
import java.awt.*;
import javax.swing.*;
public class Gantts extends JFrame
{
    GanttChart gantt;
    public void rawr()
    {
       Container c = getContentPane();
       gantt = new GanttChart();
       c.setLayout(new BorderLayout());
       c.add(gantt,BorderLayout.CENTER);
       repaint();
       setVisible(true);
    }

    private static final class GanttChart extends JPanel
    {
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);

            g.drawRect(10,10,70,30);
            g.drawRect(80,10,40,30);
            g.drawRect(120, 10, 80, 30);
        }
    }

    public static void main(String [] args)
    {
        JFrame frame = new Gantts();
        frame.setVisible(true);
        frame.setSize(520,300);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
}  

i tried to get make the same output that the applet displays but this time inside the JFrame. but it only shows up the frame without the painted rects.

please help..

[Bartek Myszkowski]

first idea I've got:
in the last sourcecode attached, in line 7 You have method called rawr() where You add components to JFrame but You never invoke this method so it's never added to JFrame - am I right?

[Maneesh Godbole]

Please use real words. "rly" is not a word.

Overall you are doing good.

1) Like Bartek said, you are never invoking the rawr(). After the line where you set the close operation would be suitable.
2) The setVisible should logically be the last line in your mail. In general, initialize, set attributes like icon,title etc, add children and make visible is the way to go.
3) You do not need the repaint. When you add any child to the parent before the call to visible, it draws itself. No need to explicitly invoke the repaint.
4) You got one duplicated call to setVisible in the rawr. You dont need that either, as you are going to make it visible from your main.

You also need to build and show the GUI on the EDT. Typically one should use the SwingUtilities#invokeLater. I will leave it as a search exercise for you to figure out why it needs to be done this way.

[Jhedzkie Skies]

oh hi. thank you both very much, i get it now. what i am doing wrong.

it shouldn't be a method. that should be the constructor.. to be like

 package os;
import java.awt.*;
import javax.swing.*;
public class Gantts extends JFrame
{
    GanttChart gantt;
    public Gantts()
    {
        Container c = getContentPane();
        gantt = new GanttChart();
        c.setLayout(new BorderLayout());
        c.add(gantt,BorderLayout.CENTER);
        setSize(520,300);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    private static final class GanttChart extends JPanel
    {
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);

            g.drawRect(10,10,70,30);
            g.drawRect(80,10,40,30);
            g.drawRect(120, 10, 80, 30);
        }
    }

    public static void main(String [] args)
    {
        SwingUtilities.invokeLater(new Runnable() {
        public void run() {
        Gantts edt = new Gantts();
        edt.setVisible(true);
        }
        });
    }
} 

also, i did tried to implement the swing utilities and its working good.

thank you again.