Thread: Dynamically Sized Scrollable JPanels

Can anyone help me figure out how to create a dynamically sized scrollable JPanel?

Here is a snippet of my code:

JPanel outputPane = new JPanel();
    	outputPane.setPreferredSize(new Dimension(525,1000));
    	...
 
    	JScrollPane scrollOutput = new JScrollPane(outputPane,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    	scrollOutput.setPreferredSize(new Dimension(550,450));

So I have already figured out that the JScrollPanel will scroll to the size of the JPanel's preferred size. Unfortunately, that doesn't help me when I add a large image to one of the JLabels inside of the JPanel at runtime. So, to achieve what I am wanting to do, I need the Scroll Pane to scroll to the ends of the JPanel, regardless of the size at the time. Any suggestions on how to do this?

Tell me if I am being unclear.

Originally Posted by copeg

When you add the image to the JPanel (or component within), first set the preferredSize of the JPanel (or component within) so that it incorporates the full size of the image (or whichever dimensions you wish - the necessity of this step may depend upon the component you are using and if its preferredsize is set when setting the image). Next, call revalidate() on the JPanel, which should notify the JViewport of the JScrollPane to recalculate the scrollable with and height.

Well, when the JFrame is begins there is not image on the JLabel. It is only after the user's input does an image load. Before then, I have no idea what the size of the image will be.

So I added outputPane.revalidate() at the end of the code that loads the image, but nothing happened.

This is the best I could do to replicate the issue in a way that I can actually show (work restrictions):

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Dimension;
 
public class PictureFrame 
{
	static JFrame frame;
	static JPanel panel;
	static JScrollPane scrollPane;
	static JLabel pictureLabel;
	static JButton loadPic;
 
    public static void main(String[] args) 
    {
    	//Build JFrame
    	frame = new JFrame("Picture Frame");
    	frame.setSize(500,500);
    	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
    	//Build JPanel
    	panel = new JPanel();
    	panel.setPreferredSize(new Dimension(300,300));
    	//Build JScrollPane
    	scrollPane = new JScrollPane(panel,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    	scrollPane.setPreferredSize(new Dimension(300,300));
 
    	//Create Blank JLabel
    	pictureLabel = new JLabel();
    	//Create JButton
    	loadPic = new JButton("Load Koala");
    	//Add Action Listener
    	loadPic.addActionListener(new ActionListener(){
    		public void actionPerformed(ActionEvent e)
    		{
    			//Set JLabel's Image to the Koala picture
    			pictureLabel.setIcon(new ImageIcon("Koala.jpg"));
    			//Revalidate
    			panel.revalidate();
    		}
    	});
    	//Add JLabel to JPanel
    	panel.add(pictureLabel);
 
    	//Get JFrame's Content Pane
    	Container contentPane = frame.getContentPane();
    	//Set Layout
		contentPane.setLayout(new FlowLayout());
    	//Add JButton and JPanel
    	contentPane.add(loadPic);
    	contentPane.add(panel);
 
    	//Set Frame Visible
    	frame.setVisible(true);
    }
}

The Koala.jpg image is a default image in Windows 7. I'll attach it if you feel like running the code to see what is happening.

Originally Posted by copeg

Cool. The first thing at least with this code, is that you are adding the panel to the frame instead of the JScrollPane. Next, if I run the code setting the preferredsize as follows, it works for me:

ImageIcon icon = new ImageIcon("Koala.jpg");//create the image icon
panel.setPreferredSize(new Dimension(icon.getIconWidth(), icon.getIconHeight()));//set the preferred size
pictureLabel.setIcon(icon);
panel.revalidate();

Ok, so I overlooked something very significant when I wrote my code example earlier. The Scrollable Panel does not just contain the JLabel. Specifically, my full program's Scrollable Panel will contain 3 JLabels (each with varying sizing images) and 3 JTextAreas (also scrollable for the time being, but that may change for style reasons).

To reflect that, I have changed the code a little to include a JTextField in the Scrollable Panel with the JLabel. Just like in my real program, the text in the JTextField (instead of the JTextArea in my real program) is set via a file read (although my example below uses FileReader instead of a stream like in my real program). Here is the changed code:

import javax.swing.*;
import java.io.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Dimension;
 
public class PictureFrame 
{
	static JFrame frame;
	static JPanel panel;
	static JScrollPane scrollPane;
	static JLabel pictureLabel;
	static JButton loadPic;
 
	//New Addition
	static JTextField textField;
 
    public static void main(String[] args) 
    {
    	//Build JFrame
    	frame = new JFrame("Picture Frame");
    	frame.setSize(500,500);
    	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
    	//Build JPanel
    	panel = new JPanel();
    	panel.setPreferredSize(new Dimension(300,300));
    	//Build JScrollPane
    	scrollPane = new JScrollPane(panel,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    	scrollPane.setPreferredSize(new Dimension(300,300));
 
    	//Create Blank JLabel
    	pictureLabel = new JLabel();
    	//Create JTextField
    	textField = new JTextField(10);
    	//Create JButton
    	loadPic = new JButton("Load Koala");
    	//Add Action Listener
    	loadPic.addActionListener(new ActionListener(){
    		public void actionPerformed(ActionEvent e)
    		{
    			//Set JLabel's Image to the Koala picture
    			pictureLabel.setIcon(new ImageIcon("Koala.jpg"));
    			try{
	    			BufferedReader in = new BufferedReader(new FileReader("text.txt"));
	    			textField.setText(in.readLine());
	    			in.close();
    			}catch(Exception ex){System.out.println("Error: "+ex);	}
 
    			//Revalidate
    			panel.revalidate();
    		}
    	});
    	//Add JLabel to JPanel
    	panel.add(pictureLabel);
    	//Add JTextField
    	panel.add(textField);
 
    	//Get JFrame's Content Pane
    	Container contentPane = frame.getContentPane();
    	//Set Layout
		contentPane.setLayout(new FlowLayout());
    	//Add JButton and JPanel
    	contentPane.add(loadPic);
    	contentPane.add(panel);
 
    	//Set Frame Visible
    	frame.setVisible(true);
    }
}

And here is the content of text.txt for this example:

This is the text.

------------------------------------------------------------------------------------------------------------------------

Perhaps I am approaching this the wrong way, so I'll just outline the purpose of what I am doing and maybe someone will know a better way.

Basically, I am creating one of those basic tutorial/content helper things that exist on programs to allow the user to learn how to use certain features. I have a JTree on the left side that contains different categories and subcategories of different features. To the right of that I will have a panel that will update based on the selected item in the JTree to present the information on how to use the selected feature. To make it as editable as possible after production, the images are being stored as basic jpg (to allow changing if necessary) and the text is being stored in basic .txt files (to also allow changing if necessary). For my initial attempt at this and to provide a basic working product, I am assuming all feature details will consist of a maximum of 3 pictures and 3 blocks of text. After I have a basic version working and I get feedback on the design and whatnot, I will make it more dynamic, hopefully so the number of JLabels and JTextAreas depend on what is required for each category.

Am I approaching this the wrong way?

Originally Posted by Darryl.Burke

Sounds like you're reinventing JavaHelp.
Developing and Delivering Better Documentation with the JavaHelp System
Knopf Online: Sample JavaHelp System

db

The company I work for isnt too wild about the idea of external libraries. As is, we are purchasing SmartXLS for this particular project.