Removing a JComponent Dynamically

[john latham]

Now that i can add a component dynamically, i would like to also remove it when needed.

How would i go about this, currently this is what im doing in my actionPerformed method:

if the checkbox is checked add the graph to the panel, if unchecked remove it from the panel. The problem is im making the panel on the fly so i cant use .remove to get rid of it, or can I? Here is my attempt

LineGraphGui l = new LineGraphGui("Node "+row, "Time", "Temperature"); 
        
        if(graph) {
        lineGraphPanel.add(l);
        lineGraphPanel.validate();      
        }
        
        else {
        this.lineGraphPanel.remove(l);
        lineGraphPanel.validate();  
        }

[ September 07, 2006: Message edited by: john latham ]

[Michael Dunn]

a lot depends on where this is
LineGraphGui l = new LineGraphGui("Node "+row, "Time", "Temperature");

if it is part of the method that adds, then remove(l) will not be referring to
the previously added (l), but to the new (l) just created.

here's a simple demo using a checkbox to add/remove

    
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Testing extends JFrame
{
  JCheckBox cbx = new JCheckBox("Add/Remove");
  JPanel p = new JPanel();
  JButton btn = new JButton("OK");
  public Testing()
  {
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    getContentPane().add(p,BorderLayout.CENTER);
    JPanel p1 = new JPanel();
    p1.add(cbx);
    getContentPane().add(p1,BorderLayout.SOUTH);
    setSize(400,300);
    setLocationRelativeTo(null);
    cbx.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent ae){
        if(cbx.isSelected())
        {
          p.add(btn);
          p.revalidate();
          p.repaint();
        }
        else
        {
          p.remove (btn);
          p.revalidate();
          p.repaint();
        }
      }
    });
  }
  public static void main(String[] args){new Testing().setVisible(true);}
}

[john latham]

Hmm i see what you mean, but is it possible to add something i create as an anyonous class and remove it? Because i dont want to make a graph unless the user asks for it.

like this:

if(graph) {
lineGraphPanel.add(new LineGraphGui("Node "+row, "Time", "Temperature"));
lineGraphPanel.validate();
}

else {
this.lineGraphPanel.remove(???);
lineGraphPanel.validate();
}

[Michael Dunn]

try this
(but instanceof can have it's own little problems, if not careful)

    
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Testing extends JFrame
{
  JCheckBox cbx = new JCheckBox("Add/Remove");
  JPanel p = new JPanel();
  JButton btn = new JButton("OK");
  public Testing()
  {
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    getContentPane().add(p,BorderLayout.CENTER);
    JPanel p1 = new JPanel();
    p1.add(cbx);
    p.add(new JTextField(5));
    getContentPane().add(p1,BorderLayout.SOUTH);
    setSize(400,300);
    setLocationRelativeTo(null);
    cbx.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent ae){
        if(cbx.isSelected())
        {
          p.add(btn);
          p.revalidate();
          p.repaint();
        }
        else
        {
          Component[] comps = p.getComponents();
          for(int x = 0, y = comps.length; x < y; x++)
          {
            if(comps[x] instanceof JButton)
            {
              p.remove (x);
              p.revalidate();
              p.repaint();
              break;
            }
          }
        }
      }
    });
  }
  public static void main(String[] args){new Testing().setVisible(true);}
}

[john latham]

It works, thank you very much!! Ive never used instanceof before, its very useful.