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Layout question

ctjoumas
ctjoumas asked
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Last Modified: 2010-03-31
I have a panel that will have other panels dynamically added to it.  What I want to do is to add all of the panels in a vertical line, one on top of the other, but keeping their respective width and height (i.e. - not resizing to fit the parent panel).  So, the end result would be:

------------------
|     panel       |
-------------------
|     panel       |
-------------------
|     panel       |
------------------
|                    |
|                    |
|                    |
|                    |
|                    |
------------------

So, below that third panel is just empty space.  Hopefully this picture comes out :)

Thanks!
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Top Expert 2006

Commented:
You can use something like this:


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

class PanelLayout extends JPanel {

  public PanelLayout() {
    super(new BorderLayout());
    currentPanel = this;
  }

  private JPanel currentPanel;

  public void addPanel(JPanel newPanel) {
    JPanel flowPanel = new JPanel(new FlowLayout());  // to keep the original width
    flowPanel.add(newPanel);
    currentPanel.add(flowPanel, BorderLayout.NORTH);
    JPanel borderPanel = new JPanel(new BorderLayout());  // to use as center panel
    currentPanel.add(borderPanel, BorderLayout.CENTER);
    currentPanel = borderPanel;
  }

  public static void main(String[] args) {
    JPanel panel1 = new JPanel();
    JPanel panel2 = new JPanel();
    JPanel panel3 = new JPanel();
    JPanel panel4 = new JPanel();

    panel1.setBackground(Color.BLUE);
    panel2.setBackground(Color.RED);
    panel3.setBackground(Color.ORANGE);
    panel4.setBackground(Color.GREEN);

    panel1.add(new JLabel("<html>hello world 1</html>"));
    panel2.add(new JLabel("<html>hello world 2<br>hello world 2</html>"));
    panel3.add(new JLabel("<html>hello world 3<br>hello world 3<br>hello world 3</html>"));
    panel4.add(new JLabel("<html>hello world 4<br>hello world 4<br>hello world 4<br>hello world 4</html>"));

    PanelLayout test = new PanelLayout();
    test.addPanel(panel1);
    test.addPanel(panel2);
    test.addPanel(panel3);
    test.addPanel(panel4);

    JFrame myFrame = new JFrame();
    myFrame.getContentPane().setLayout(new BorderLayout());
    myFrame.getContentPane().add(test, BorderLayout.CENTER);
    myFrame.pack();
    myFrame.setVisible(true);
  }

}
Java Developer
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Top Expert 2010
Commented:
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Top Expert 2006

Commented:
>  Use a BoxLayout
That makes it a little easier indeed.  But i guess you still need to use additional panels with FlowLayout if you want to keep the original width:


class PanelLayout extends JPanel {

  public PanelLayout() {
    super();
    setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
  }

  public void addPanel(JPanel newPanel) {
    JPanel flowPanel = new JPanel(new FlowLayout());
    flowPanel.add(newPanel);
    add(flowPanel);
  }

}
Mick BarryJava Developer
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Top Expert 2010

Commented:
>  But i guess you still need to use additional panels with FlowLayout if you want to keep the original width

No BoxLayout would allow the panels to keep a certain width.
Top Expert 2006

Commented:
I don't use BoxLayout much, but from my tests, it seems that each panel will get the same width, which is the width of the widest panel...
Mayank SPrincipal Technologist
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Commented:
Top Expert 2006

Commented:
BoxLayout is pretty nice indeed...  I'll try to use it more often.
From the "how to use BoxLayout" page, it seems that the width of the added components will be set to their MaximumWidth.
For JButtons, MaximumWidth = PreferredWidth, but not for JPanels, which makes the JPanel take the width of the widest component.
If you set the MaximumSize to the PreferredSize, you get different widths for your JPanels, but then the layout gets quite uggly.
There must be ways to tune it, but i find it easier to just put each JPanel in a new JPanel with FlowLayout.

Author

Commented:
Actually, I couldn't get it to work with BoxLayout.  As the main panel was resized (in the vertical direction), the panels that were added expanded to fit the panel.  So, in the "drawing" I provided in my first post, those three panels will expand the entire panel.

I can get this to work with SpringLayout on the subpanels itself (which I don't really get...but it works).  However, if there is a way to get it to work with BoxLayout, I would probably prefer that.

Author

Commented:
Ahh..actually, I got it.  When the panels are finished being added, I just add a Box.createVerticalGlue() to the main panel.  I gotta run, but ill be back to give the points out :)

Thanks!!!
Mayank SPrincipal Technologist
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Commented:
Glad to know you made it ;-)

Author

Commented:
Thanks for all of your help - I guess I shoulda remembered about that verticalGlue guy...
Mick BarryJava Developer
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Top Expert 2010

Commented:
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