Dynamically Resize a JScrollPane?

Question

I Have two files. One extends JFrame, and another Extends JPanel. Whenever I change the size of the frame, whether it be maximizing, dragging, whatever, i want the ScrollPane to fit itself to the current size of the frame. There's more to it, there's a top menubar and a bottom bar as well, but i left those out for simplicity.

Essentially, i want it to work like notepad.

right now, I use a ComponentListener on the frame that calls a setSize method in the the other class. The setSize method is just:

public void resize(int x, int y)
{
textA.setPreferredSize(new Dimension(x, y-50));

areaScrollPane.setPreferredSize(new Dimension(x,y-50));
}

also, for reference:

public void componentResized(ComponentEvent e)
 {
     textA.resize(panel.getWidth(),panel.getHeight());
  }

FYI, it extends JPanel because of the way I add it to the frame:

panel = (JPanel) this.getContentPane();
panel.setLayout(new BorderLayout());
panel.add(textA, BorderLayout.CENTER);

so what's the best way to do this? Thanks!

Edit: Here's the scrollpane file. It's called textA in my main.

    public class TextArea extends JPanel
    {

    JTextArea textA=new JTextArea(500,500);

    JScrollPane areaScrollPane = new JScrollPane(textA);
    Toolkit toolkit =  Toolkit.getDefaultToolkit ();
    Dimension dim = toolkit.getScreenSize();
    Dimension dim2=(new Dimension((int)(dim.getWidth()),(int)(dim.getHeight()-120)));
    public TextArea()
    {
        //textA.setLineWrap(true);
        //textA.setWrapStyleWord(true);
        textA.setEditable(true);
        textA.setForeground(Color.WHITE);

        textA.setBackground(Color.DARK_GRAY);
        this.setFont(null);



        areaScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        areaScrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        areaScrollPane.setMinimumSize(new Dimension(300,300));
        areaScrollPane.setSize(new Dimension(800,800));
        textA.setPreferredSize(dim2);
        areaScrollPane.setPreferredSize(dim2);
        areaScrollPane.setMaximumSize(dim2);
        add(areaScrollPane);
     }


    @Override
    public void resize(int x, int y)
    {
    textA.setPreferredSize(new Dimension(x, y-50));
    areaScrollPane.setPreferredSize(new Dimension(x,y-50));
    }

    }

and the main:

    public class JEdit extends JFrame implements ComponentListener

    {
    TextArea textA=new TextArea();
    JPanel panel;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)
    {

       JEdit run=new JEdit();

    }

    public JEdit()
    {

        setTitle("JEdit");
        setLayout(new BorderLayout());
        setSize(1100, 1000);

        this.setMinimumSize(new Dimension(100,100));
        //setBackground(Color.BLACK);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (ClassNotFoundException ex) {
           System.out.println("error1");
        } catch (InstantiationException ex) {
            System.out.println("error2");
        } catch (IllegalAccessException ex) {
           System.out.println("error3");
        } catch (UnsupportedLookAndFeelException ex) {
            System.out.println("error4");
        }

         panel = (JPanel) this.getContentPane();
         panel.setLayout(new BorderLayout());
         //TopBar top=new TopBar();
        // PositionBar posB=new PositionBar();
         panel.add(textA, BorderLayout.CENTER);




       // add(top,BorderLayout.NORTH);
       // add(posB,BorderLayout.SOUTH);




        addComponentListener(this);
        setVisible(true);

    }



    public void componentResized(ComponentEvent e)
    {
         textA.resize(panel.getWidth(),panel.getHeight());
    }

    public void componentMoved(ComponentEvent e) {
    textA.resize(panel.getWidth(),panel.getHeight());
    }

    public void componentShown(ComponentEvent e) {
    textA.resize(panel.getWidth(),panel.getHeight());
    }

    public void componentHidden(ComponentEvent e) {
         textA.resize(panel.getWidth(),panel.getHeight());
    }



    }

You where told there is no need to set any preferred size or use any kind of listener. You where also told that you add the scrollpane directly to the frame, yet you added it to a JPanel. Make an effort to actually try the suggestions if you want help! — camickr, Jun 05 '11 at 03:02

Hovercraft Full Of Eels · Accepted Answer · 2011-06-05T03:22:55.097

Regarding the code you've posted, for one get rid of all calls to setSize -- these are generally not honored when using layout managers and get rid of all of your ComponentListener stuff as it's superfluous since you are using layout managers to resize things. The biggest problem I see though is that your allow your TextArea JPanel to use its default layout, which is FlowLayout, and doing so will prevent the JScrollPane that it holds from resizing. Give this class a BorderLayout (or better simply return a JScrollPane from the class), and you're set. e.g. with quick modifications and with renaming of classes to prevent clashes with the standard Java classes,

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

@SuppressWarnings("serial")
public class JEdit2 extends JFrame  {
   TextArea2 textA = new TextArea2();
   JPanel panel;

   public static void main(String[] args) {
      new JEdit2();
   }

   public JEdit2() {
      setTitle("JEdit 2");
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      panel = (JPanel) this.getContentPane();
      panel.add(textA, BorderLayout.CENTER);

      pack(); //!! added
      setLocationRelativeTo(null);
      setVisible(true);
   }

}

@SuppressWarnings("serial")
class TextArea2 extends JPanel {
   JTextArea textA = new JTextArea(500, 500); // !! this is one friggin' huge JTextArea!
   JScrollPane areaScrollPane = new JScrollPane(textA);

   public TextArea2() {
      textA.setEditable(true);
      textA.setForeground(Color.WHITE);
      textA.setBackground(Color.DARK_GRAY);
      this.setFont(null);

      setLayout(new BorderLayout()); //!! added
      add(areaScrollPane, BorderLayout.CENTER);
   }
}

perfect! If you wouldn't mind, what is the purpose of pack(); Thanks! — Nyx, Jun 05 '11 at 03:30

score 3 · Answer 2 · answered Jun 05 '11 at 02:43

3

By default a JFrame uses a BorderLayout (so there is no need to reset it). All you need to do is add the JScrollPane to the CENTER of the BorderLayout and it will resize automatically.

And the basic code would be:

JTextArea textArea = new JTextArea(...);
JScrollPane scrollPane = new JScrollPane();
frame.add(scrollPane, BorderLayout.CENTER);

I'm not sure why you are adding the text area to the center.

There is no need to use setPreferredSize() on any component or use a listener on any component.

If you need more help then you need to post a SSCCE.

answered Jun 05 '11 at 02:43

camickr

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textA is my jscrollpane file. Didnt clarify that. – Nyx Jun 05 '11 at 02:47
You added the scroll pane to a panel, not the frame, therefore the panel gets resized, not the scrollpane. – camickr Jun 05 '11 at 03:05
alright, i took your code and tried it in my main, and it works just like you said. So how would i modify my textArea file so that it does the same thing? Should it extend JTextArea or what? Thanks again. – Nyx Jun 05 '11 at 03:16
There is no need for a TextArea class at all. You aren't adding any new functionality to the text area. Just do what I did, create JtextArea and add it to a JScrollPane. – camickr Jun 05 '11 at 03:24

Dynamically Resize a JScrollPane?

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