Difficulties with removeAll() on a JFrame

[SkittlesAreYum]

What I want to do is reuse a frame again and again, but each time it will have different components, so I need to remove all the old ones. So, I'm trying to use the removeAll() method to take all the components off, and then add new ones later. For example:

--all neccessary imported packages--
JFrame myFrame = new JFrame();
JLabel label1 = new JLabel("hello");

take all components off, and add new ones
myFrame.removeAll();
JLabel label2 = new JLabel("hello again");

Well, the removeAll() method works like a charm. In fact, it works so damn well that I cannot add anything more to the frame. label2, for example, won't show up. My teacher suggested using myFrame.validate() after I removeAll, but that doesn't help. What is the problem here? Can anyone help?

Thanks in advance.

[abc123]

.repaint()
.refresh()

can't quite remember...

for the record, try resizing the frame after you've done .removeAll() and then added some things.. if they show up after the resizing id suggest its .repaint() you need.

( resizing as in grab corners with mouse and drag ).

[SkittlesAreYum]

It's repaint(), but that doesn't work either. I'm still left with a blank frame. And physically resizing the frame doesn't help either way, either. Dang it.

[abc123]

then id suggest they aren't on the frame..

what is the code u do for adding them? because what u've posted up there obviously doesn't add either label to those frames....

[SkittlesAreYum]

Okay, here's the full code of an example I'm trying to get to work, just as a test program. Just paste the whole thing into TextPad or whatever, it should run.



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

public class X
{
private static JFrame xFrame;
public static void main(String[] args)
{
xFrame = new JFrame();
xFrame.setSize(100,100);
JButton xButton = new JButton("X");
xButton.addActionListener(new XListener());
xFrame.getContentPane().add(xButton);
xFrame.setVisible(true);
}

private static class XListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
xFrame.removeAll();
xFrame.validate();
xFrame.hide();
xFrame.show();

xFrame.getContentPane().add(new JLabel("Java is stupid"));
}
}
}

[abc123]

xFrame.getContentPane().add(new JLabel("Java is stupid"));

after that you tried:

xFrame.repaint();

and it didn't work?

.. it should...

[SkittlesAreYum]

Well, no I hadn't tried that. But I just did, and still a no-go. Why am I so good at messing up Java? I always stump my teacher with crap like this.

Thanks for your constant help, abc.

[abc123]

yes, okay, .removeAll() seemingly removes .. everything, so i think you need to add a content pane again... how, i don't exactly know, but thats your problem

[SkittlesAreYum]

I've tried remaking the Container (getContentPane()) for the frame, and it doesn't work either. However, check out this my teacher made:

public class Xnew
{
private static JFrame xFrame;
private static JPanel xPanel;
public static void main(String[] args)
{
xFrame = new JFrame();
xPanel = new JPanel();

xFrame.setSize(100,100);
JButton xButton = new JButton("X");
xButton.setEnabled(true);
xButton.addActionListener(new XListener());
xPanel.add(xButton);
xFrame.getContentPane().add(xPanel);
xFrame.setVisible(true);
}

private static class XListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
xPanel.removeAll();
xPanel.add(new JLabel("Java is stupid"));
xPanel.updateUI();
}
}
}

Making the label on a JPanel allows it to display after everything else is removed. To top it all off, the JPanel is NOT removed by removeAll().

Should we just give up now and say removeAll() is bugged?

[abc123]

no no, its not bugged, the jpanel isn't removed because .removeAll is called on the panel itself, not the frame..

i think my prior suggestion is still true; removeAll gets rid of everything, you need to add a new contentPane to it in order to get it to display the items..


... it seems.

[SkittlesAreYum]

I modified the first (X) program so a Container is declared right above where the label is added. Then I modified the line where the label is added so it appears as below.

Container contentPane = xFrame.getContentPane();

contentPane.add(new JLabel("Java is stupid"));

And it still won't work. Grrr. Thanks for your help, I'm going to bed right now, I'll check this tommorow.

[jeff]

Hi,

Notice that when you first add your button, you're adding it to the JFrame's content pane. The content pane is where you're supposed to add components to a JFrame.

see:
http://java.sun.com/docs/books/tutor.../toplevel.html

Later in your application, you're calling removeAll directly on the JFrame. This removes the content pane and other panes mentioned in the above URL. You don't really want to be doing this. Instead, call getContentPane().removeAll(). This will restore the JFrame back to how it was before you added any components.

Then, add your new components to the content pane and call:

invalidate
revalidate
repaint

on it.

So, the body of your actionListener could look like this:

xFrame.getContentPane().removeAll();
xFrame.getContentPane().add(new JLabel("Java is NOT stupid"));
xFrame.getContentPane().invalidate();
xFrame.getContentPane().validate();
xFrame.getContentPane().repaint();

I've tried this with your code and it fixes the problem.