Thread: jsplipane and resizing

Hello, newbie here.
I want to do a three way split with jsplipane (two panels on top and one at bottom).
And I want the top-left panel to remain a square no matter what. When the user moves either the vertical or horizontal splitpane (or window is resized in other ways), the three panels are to be adjusted so that the top-left pane remains a square but with different dimension. How do I achieve that ?

thank you,

Can anyone help please? Maybe i asked the question in the wrong forum ?

Originally Posted by KevinWorkman

Just a word to the wise, bumping your thread like that actually decreases your chances of getting help- people will see that the post has been replied to already, so they'll move on to one with zero replies instead.

Sorry but I disagree. People may equally have thought I found a solution somewhere else which I didn't. I waited for two days (48 hours as advised when I registered in the forum) before bumping... I would say that is fair, no ?

But you can nest JSplitPanes, and put a PropertyChangeListener on each JSplitPane that sets the value of the other JSplitPane divider as appropriate.

Recommended reading: How to Use Split Panes (The Java™ Tutorials > Creating a GUI With JFC/Swing > Using Swing Components)
MultiSplitPane: Splitting Without Nesting | Java.net

Thanks for the tip. I read the whole of the first link and a lot of other pages before I posted my question here but none addressed the problem I was having.
Also I needed to do the same thing when the window is re-sized, so I was hoping there would a "panel needs resizing" event that I can use to calculate and override the width and height.

I tried your idea but it doesn't work. When any of them gets moved I set the others splitpane position to 0.5 but it doesn't work as intended (sometimes it does).
When the window is resized by dragging the frame, this listener doesn't sense it at all.
So my question still remains unanswered if someone wants to help..

import java.awt.BorderLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
 
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JSplitPane;
 
public class Hello {
	public static void main(String args[]) {
		JFrame frame = new JFrame("Property Split");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		JComponent b1 = new JButton("A");
		JComponent b2 = new JButton("B");
		JComponent b3 = new JButton("C");
		final JSplitPane hpane1 = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,b1,b2);
		final JSplitPane hpane2 = new JSplitPane(JSplitPane.VERTICAL_SPLIT,hpane1,b3);
 
		PropertyChangeListener propertyChangeListener = new PropertyChangeListener() {
			public void propertyChange(PropertyChangeEvent changeEvent) {
				JSplitPane sourceSplitPane = (JSplitPane) changeEvent.getSource();
				String propertyName = changeEvent.getPropertyName();
				if (propertyName.equals(JSplitPane.LAST_DIVIDER_LOCATION_PROPERTY)) {
					if(sourceSplitPane == hpane1)
						hpane2.setDividerLocation(0.5);
					else
					    hpane1.setDividerLocation(0.5);
					System.out.println(" " + hpane1.getDividerLocation() 
							         + " " + hpane2.getDividerLocation()
							         );
				}
			}
		};
 
		hpane1.addPropertyChangeListener(propertyChangeListener);
		hpane2.addPropertyChangeListener(propertyChangeListener);
 
		frame.add(hpane2, BorderLayout.CENTER);
		frame.setSize(300, 150);
		frame.setVisible(true);
	}
}

That's not exactly what I said to do- I wouldn't expect setting both to .5 to accomplish your goal. You're going to have to figure out what the dimensions of the square for the upper-left component should be, which is going to be different depending on which JSplitPane was resized.

Ofcourse, that was just a quick example. My actual goal is to avoid distortion of an image in a panel. So once I know the dimensions of the image, I would enforce the location of the splitpanes in such a way that the image is not distorted in any way (only scaled up or down).

Again, I wouldn't expect it to. That's a different listener, which I mentioned above.

Another thing you might want to take into account is whether setting the divider location inside the PropertyChangeListener triggers the listener, which sets the divider location, which triggers the listener... which might lead to weird behavior.

Exactly. This method sounds recursive and has already given me weird behaviours. So instead of listening for splitpane movements, I would prefer listening to resizing event for the panel which contains the image (if there is one). Only one listener will be needed in that case. But even with that I am afraid there could be the same problem... Maybe if there is an event which tells "component is about to be resized" ?

 public void componentResized(ComponentEvent e) {
        Dimension dim = getcomponesize ....
        Adjust dim ....
        Resize this component (triggers recursion) ...
    }

I have not tried it, so I will come back with the result later.
thanks.