Drawing a square with a button

[javstudent]

Hi,

I'm using NetBeans IDE 6.9.1 and I am trying to draw square once a button is pressed.

I have 3 classes.

Graphic class:

import java.awt.Color;
import javax.swing.JPanel;
import java.awt.Graphics;
/**
*
* @author
*/
public class Graphic extends JPanel
{

@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(5, 5, 20, 20);
}

}

The code for the button in my NewJFrame class generated by NetBeans IDE

private void button2ActionPerformed(java.awt.event.ActionEvent evt) {
Graphic graphic = new Graphic();
jPanel2.add(graphic);// TODO add your handling code here:
}

My Main class:

package javaapplication9;

/**
*
* @author */
public class Main
{
public static void main(String args[])
{
java.awt.EventQueue.invokeLater(new Runnable()
{
public void run() {
new NewJFrame().setVisible(true);
}
});
}
}

When I press my button, the square does not display. Is it possible to add a component to another JPanel ( which is also a component )?

[Fubarable]

You may need to repaint and revalidate the container that holds the newly added component.

[javstudent]

You mean repaint and revalidate jPanel2?

[Fubarable]

You mean repaint and revalidate jPanel2?

Yes, if this is the container that holds the Graphic JPanel. Also you sometimes have to repack your top-level window (JFrame?) so as to allow components to shift and allow room for the new component. Layout managers of course are key for this too.

[javstudent]

I made another application just to test out the button and I used the repaint() method and it still does not work. So what I have is this:

My Square class

package javaapplication10;
import java.awt.Color;
import javax.swing.JPanel;
import java.awt.Graphics;
/**
*
* @author
*/
public class Square extends JPanel
{
@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(5, 5, 20, 20);
}

}

My Drawing Class

package javaapplication10;
import javax.swing.JFrame;

/**
*
* @author
*/
public class Drawing extends JFrame
{
/** Creates new form Drawing */
public Drawing()
{
initComponents();
}


/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

jButton1 = new javax.swing.JButton();

setDefaultCloseOperation(javax.swing.WindowConstan ts.EXIT_ON_CLOSE);

jButton1.setText("jButton1");
jButton1.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jButton1MouseClicked(evt);
}
});

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout .Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILI NG, layout.createSequentialGroup()
.addContainerGap(277, Short.MAX_VALUE)
.addComponent(jButton1)
.addGap(50, 50, 50))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout .Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILI NG, layout.createSequentialGroup()
.addContainerGap(266, Short.MAX_VALUE)
.addComponent(jButton1)
.addContainerGap())
);

pack();
}// </editor-fold>

private void jButton1MouseClicked(java.awt.event.MouseEvent evt) {
Square k = new Square();
add(k);
repaint();
// TODO add your handling code here:
}

/**
* @param args the command line arguments
*/

My Main class

package javaapplication10;

/**
*
* @author
*/
public class Main
{


public static void main(String[] args)
{
java.awt.EventQueue.invokeLater(new Runnable()
{
public void run()
{
new Drawing().setVisible(true);
}
});
}// TODO code application logic here
}

I am telling the container, in this case the class Drawing, to repaint once the panel component is added. Don't know where to go from here....

[javstudent]

Any takers? I also tried the revalidate method as well and it still did not work.

[Fubarable]

Your problem is likely with layouts, and I'll bet that after you create your Square object and add it to your gui, if you check it's size it's 0 x 0. Do not use NetBeans to generate your code, read the tutorials on how to use layout managers, and add your new JPanel to a container that uses a layout manager that will allow the square to be seen. Also, when posting code here, please don't use "quote" tags, but rather use "code" tags else your code will not be readable.

[javstudent]

Thank you!

I will check the size and try to figure out how to edit the code (Netbeans doesn't allow the code to be edited by default) so that I can use layout managers.

[Fubarable]

Thank you!

I will check the size and try to figure out how to edit the code (Netbeans doesn't allow the code to be edited by default) so that I can use layout managers.

You can use different layout managers in NetBeans-generated code, but again, I'm advising you to not use NetBeans-generated code. Create the Swing program by hand as it will be easier to do what you want and you'll have more control over your program and a greater understanding as to what it's doing and why.

[javstudent]

I have been reading about layout managers and I seem to not want to use them for certain instances. I can add panels to frames and add panel within panels without problem using just pure code and not IDE. However, when I try to paint an oval within a panel, it either removes the background color of the panel and adds the oval or it retains the color of the panel but the blue oval is not showing.

This is the code that I have for my

Main class

package javaapplication13;

/**
 *
 * @author
 */
public class Main
{

    public static void main(String[] args)
    {
        Frame f = new Frame();

    }

}

My Frame class

package javaapplication13;
import javax.swing.JFrame;
import java.awt.Color;
import javax.swing.JPanel;
import javax.swing.BoxLayout;

/**
 *
 * @author 
 */
public class Frame extends JFrame
{
    public Frame()
    {
        initComponents();
    }

    private void initComponents()
    {
       //Tcell2 t =  new Tcell2();
       getContentPane().setBackground(Color.GREEN);
       setSize(800, 600);
       setResizable(true);
       setVisible(true);
       setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       setLayout(null);

       JPanel j =  new JPanel();
       j.setSize(200,200);
       j.setBackground(Color.RED);
       j.setLocation(100, 200);

       //JPanel j2 =  new JPanel();
       //j2.setSize(20,20);
       //j2.setBackground(Color.BLUE);
       //j2.setLocation(4, 5);

       Tcell2 t =  new Tcell2();
       
       BoxLayout box = new BoxLayout(j,BoxLayout.LINE_AXIS);
       j.setLayout(box);

       add(j);
       j.add(t);
       System.out.println(t.isShowing());
       System.out.println(j.isShowing());
       j.validate();
       j.repaint();

 
    }

}

and my Tcell2 class which draws the blue oval.

package javaapplication13;
import java.awt.Color;
import javax.swing.JPanel;
import java.awt.Graphics;
/**
 *
 * @author 
 */
public class Tcell2 extends JPanel
{
    public Tcell2()
    {

    }
    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.setColor(Color.BLUE);
        g.fillOval(5, 5, 30, 30);
    }

}

In my Frame class, I have it showing that my components j and t are showing because they give a readout of true. However, I am still puzzled on why my background for the jpanel essentially dissappears? Any takers?

[Fubarable]

The red background-containing JPanel is there, but is covered by the other JPanel that was added. To see what I mean, please make the other panel not opaque:

class Tcell2 extends JPanel {
   public Tcell2() {
      setOpaque(false); 
   }

The BoxLayout tutorial and api will tell you why the second panel completely covers the first. Also, and again, you'll want to avoid using null layouts. Just because it's easier to use at this stage doesn't make them better to use as you'll find out when you get into more complex layouts.