JScrollPane doesn't work with JTextArea

Question

I'm trying to add the ScrollPane to my TextArea, but it doesn't appear. Here's the code:

import javax.swing.*;

public class PracownikGui extends JFrame {

private JPanel Panelek;
private JTextArea Tekscik;
private JScrollPane Skrol;

public PracownikGui() {

    setMinimumSize(new Dimension(600, 600));
    setLocationRelativeTo(null);
    setContentPane(Panelek);
    setResizable(false);
    setDefaultCloseOperation(DISPOSE_ON_CLOSE);

    Tekscik();

public void Tekscik() {
    Tekscik = new JTextArea(2, 10);
     Skrol = new JScrollPane( Tekscik );
     Tekscik.setSize(300, 300);
     Tekscik.setLocation(20, 70);
     Tekscik.setEditable(true);
     Tekscik.setLineWrap(true);
      add(Tekscik);
}}

Any help, please.

Answer 1

I made quite a few changes to your code. Your code wouldn't run.

Here's the GUI I created.

As you can see, there's a vertical scroll bar. The default action for the scroll bar is that it doesn't appear until you've filled the JTextArea with text.

Here are the important changes I made to your code.

1. Class names start with a capital letter. Method names and variable names start with a lower case letter.

2. A Swing application must start with a call to the SwingUtilities invokeLater method. This ensures that the Swing components are created and used on the Event Dispatch thread (EDT). Since the invokeLater method requires a Runnable, I had the PracownikGui class implement Runnable.

3. You use Swing components. You don't extend Swing components, or any other Java class, unless you want to override one of the methods in that class.

4. I removed all of the sizing and positioning statements, except for the statement that defines the rows and columns of the JTextArea. Hovercraft Full Of Eels explained this, but you use Swing layouts to get the arrangement of Swing components you want. The default layout for a JPanel is the FlowLayout. The default layout for a JFrame is the BorderLayout.

5. I added the JScrollPane to the JPanel. I added the JPanel to the JFrame.

Here's the code.

package com.ggl.testing;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class PracownikGui implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new PracownikGui());
    }

    private JFrame frame;
    private JPanel panelek;
    private JTextArea tekscik;
    private JScrollPane skrol;

    @Override
    public void run() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);

        panelek = new JPanel();
        tekscik(panelek);
        frame.setContentPane(panelek);

        frame.setResizable(false);
        frame.pack();
        frame.setVisible(true);
    }

    public void tekscik(JPanel panelek) {
        tekscik = new JTextArea(2, 20);
        tekscik.setEditable(true);
        tekscik.setLineWrap(true);

        skrol = new JScrollPane(tekscik);
        panelek.add(skrol);
    }
}

Answer 2

You're shooting yourself in the foot by setting a JTextArea's size or preferredSize since this prevents it from expanding into the JScrollPane:

 Tekscik.setSize(300, 300);

set its rows and columns only.

Also you need to add the JScrollPane to the GUI, not the JTextArea.

Also, while null layouts and setBounds() or setSize(...) and setLocation(...) might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.

e.g.,

import javax.swing.*;

public class PracownikPanel extends JPanel {
   private JTextArea tekscik = new JTextArea(5, 25);

   public PracownikPanel() {
      tekscik.setLineWrap(true);
      tekscik.setWrapStyleWord(true);
      JScrollPane skrol = new JScrollPane(tekscik);
      skrol.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

      add(skrol);
   }

   private static void createAndShowGui() {
      PracownikPanel mainPanel = new PracownikPanel();

      JFrame frame = new JFrame("PracownikPanel");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}