JTextField in JScrollPane

[Norm Radder]

Trying to learn Swing GUI again and have a problem.
When the following program displays its window initially, there is a text field in the middle full of characters. If I add a character to it, the scroll bar appears and obscures the text in the text field. I've tried some changes to the GridBagConstraints that give the text field more room than it need initially so that when the scroll bar is added, the text is still visible.
However, this is rather poor looking. And if after adding an extra character to the text field, I click on the window, the text field is squeezed down to only show a few characters.
Question:
How to have the layout manager re-do the layout when the scroll bar is added so that the text field has its contents appear the same size? Setting ipady gives the text field too much space without the scrollbar.

Thanks,
Norm

  
// Base64GUI
 
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class Base64GUI extends JFrame implements ActionListener {
   // Default encode string
   final String EncStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                       + "abcdefghijklmnopqrstuvwxyz"
                       + "0123456789+/";
   // Constructor ------------------------------------------------
   public Base64GUI() {
      super("Base 64 interface");
      addWindowListener(new WindowAdapter() {
//         @Override   // to test if following is really overriding an existing method
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
       });
      Container cont = getContentPane();
      JTabbedPane tabPane = new JTabbedPane();
      tabPane.add("Create Enc tab", getCreatePanel());
      cont.add(tabPane);
      pack();
      // Center frame
      Dimension ss = Toolkit.getDefaultToolkit().getScreenSize();
      setLocation((ss.width-getBounds().width)/2, 
                    (ss.height-getBounds().height)/2);  
      setVisible(true);
   }  // end Constructor
 
   //--------------------------------------------------------------------
   // Build panel for Creating a new Encode table
   // Top row will be string to use: 5 columns: 1 label, 3 Textfield
   // bottom row - buttons in column 3 
   private JPanel getCreatePanel() {
      GridBagLayout gbl = new GridBagLayout();
      JPanel jp = new JPanel(gbl);
      // See The JFC Swing Tutorial page 374
      GridBagConstraints gbc = new GridBagConstraints();
 
      JLabel jl = new JLabel("Encode table:");
      gbc.gridx = 0;
      gbc.gridy = 0;
      jp.add(jl, gbc);
 
      JTextField encStrTF = new JTextField(EncStr);
      JScrollPane jsp = new JScrollPane(encStrTF);
      // NB adding letters to this causes it to resize obscuring contents <<<<<<<<<<<<
      // Verify only valid letters entered before allowing tabbing
      encStrTF.setInputVerifier(new InputVerifier() {
         public boolean verify(JComponent input) {
            System.out.println("Verifing");
               JTextField tf = (JTextField) input;
               String str = tf.getText();
               return str.length() == 64;
         }
      });
      gbc.gridx = 1;
      gbc.gridy = 0;
      gbc.gridwidth = 3;
//      gbc.insets = new Insets(10, 0, 0 ,0); //No change when this added
      gbc.ipady = 20; //  poor looking, but gives room for resize to not obscure text
      jp.add(jsp, gbc);
 
      JPanel bPnl = new JPanel();
      JButton jb = new JButton("Create new");
      jb.addActionListener(this);
      gbc.gridx = 3;
      gbc.gridy = 1;
      gbc.gridwidth = 1;
      bPnl.add(jb);
      jp.add(bPnl, gbc);
 
      return jp;
   } // end getCreatePanel()
 
   //---------------
   public void actionPerformed(ActionEvent ae) {
      Object obj = ae.getSource();
      System.out.println("got ae: " + ae);
   }
 
   public static void main(String[] args) {
      new Base64GUI();
   } // end main()
 
} // end class
  

[Michael Dunn]

don't know if this will suit, but try setting the scrollbar policies
JScrollPane jsp = new JScrollPane(encStrTF,ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER,ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);

but is there a particular reason you want the scrollpane?
on it's own, the textfield responds to end/home/arrow keys.

also, unless you're just trying a few things:

addWindowListener(new WindowAdapter() {.........
should be replaced by
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

and

Dimension ss = Toolkit.getDefaultToolkit().getScreenSize();
setLocation((ss.width-getBounds().width)/2,(ss.height-getBounds().height)/2);
should be replaced by
setLocationRelativeTo(null);

[Norm Radder]

Thanks for the response.
What about the

if after adding an extra character to the text field, I click on the window, the text field is squeezed down to only show a few characters.

What causes that?

[Michael Dunn]

I gave up ages ago trying to understand why gridbaglayout does what it does.

I find it much easier to nest a couple of layouts to achieve the same effect.

[Campbell Ritchie]

If you are using GridBag you might need to do one or all of these to your text field:

Set its preferred size

Set an x-weight in the constraints

Set a horizontal (or both) fill in the constraints.

[pete stein]

I too try to assiduously avoid GridBagLayout, and from what I can tell, this is not a GridBagLayout problem since I was able to reproduce the problem (but no solution, sorry) by using other layouts:

import javax.swing.*;
import java.awt.*;
 
public class Base64GUI3 extends JFrame 
{
  final String EncStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
      + "abcdefghijklmnopqrstuvwxyz" + "0123456789+/";
  private JPanel jp;
  private JTextField encStrTF;
 
  public Base64GUI3()
  {
    super("Base 64 interface");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container cont = getContentPane();
    JTabbedPane tabPane = new JTabbedPane();
    tabPane.add("Create Enc tab", getCreatePanel());
    cont.add(tabPane);
    pack();
    setLocationRelativeTo(null);
    setVisible(true);
  } 
 
  private JPanel getCreatePanel()
  {
    jp = new JPanel(new BorderLayout()); 
    JPanel topPanel = new JPanel();
 
    JLabel jl = new JLabel("Encode table:");
    topPanel.add(jl);
 
    encStrTF = new JTextField(EncStr);
    JScrollPane jsp = new JScrollPane(encStrTF);
    
    topPanel.add(jsp); 
    
    jp.add(topPanel, BorderLayout.NORTH);
 
    JPanel bPnl = new JPanel();
    JButton jb = new JButton("Create new");
    bPnl.add(jb);
    jp.add(bPnl, BorderLayout.SOUTH);  
 
    return jp;
  } 
 
  public static void main(String[] args)
  {
    new Base64GUI3();
  } 
}

[ August 31, 2008: Message edited by: pete stein ]

[Norm Radder]

Thanks for the responses.
Glad to see its not just me.
Its taken hours so far for a small simple gui.
But you've all said I MUST learn Swing, so I'll continue on.

[pete stein]

The idea posted above about setting scrollbar policies worked in my SSCCE:

    encStrTF = new JTextField(EncStr);
    JScrollPane jsp = new JScrollPane(encStrTF);
    jsp.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); // ** added this **

[Avi Abrami]

Norm,
Here's a silly idea: Use JTextArea instead of "JTextField" with line-wrap set.

Good Luck,
Avi.

[Craig Wood]

Setting this up so that the textField expands/contracts with user input seems a bit unusual. Usually we seem to gravitate toward using a DocumentFilter for this kind of input–restriction behavior. But it is a fun thing to explore. Here is one way you might put it together:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class B64Rx extends JFrame implements ActionListener {
   final String EncStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                       + "abcdefghijklmnopqrstuvwxyz"
                       + "0123456789+/";
   JScrollPane scrollPane;
 
   public B64Rx() {
      super("Base 64 interface");
      setDefaultCloseOperation(EXIT_ON_CLOSE);
      Container cont = getContentPane();
      JTabbedPane tabPane = new JTabbedPane();
      tabPane.add("Create Enc tab", getCreatePanel());
      cont.add(tabPane);
      setSize(575,150);
      setLocationRelativeTo(null);  
      setVisible(true);
   }
 
   /** Build panel for Creating a new Encode table */
   private JScrollPane getCreatePanel() {
      // Initialize components.
      JLabel jl = new JLabel("Encode table:");
      JTextField encStrTF = new JTextField(EncStr) {
         protected void processKeyEvent(KeyEvent e) {
            super.processKeyEvent(e);
            scrollPane.revalidate();
         }
      };
//      JScrollPane jsp = new JScrollPane(encStrTF);
      // NB adding letters to this causes it to resize obscuring contents 
      // Verify only valid length entered before allowing tabbing
      // To verify valid letters you can use a DocumentFilter.
      encStrTF.setInputVerifier(new InputVerifier() {
         public boolean verify(JComponent input) {
            JTextField tf = (JTextField) input;
            String str = tf.getText();
            return str.length() == 64;
         }
      });
      JButton jb = new JButton("Create new");
      jb.addActionListener(this);
 
      // Focus on layout.
      // Top row will be string to use: 2 columns: 1 label, 1 Textfield
      // bottom row - button centered 
      GridBagLayout gbl = new GridBagLayout();
      JPanel jp = new JPanel(gbl);
      // See The JFC Swing Tutorial page 374
      GridBagConstraints gbc = new GridBagConstraints();
 
      gbc.gridx = 0;
      gbc.gridy = 0;
      // You could set left/right insets here to pad "jl".
      jp.add(jl, gbc);
 
      gbc.gridx = 1;
      gbc.gridy = 0;
      // You cannot use the gridwidth constraint to control column
      // size or allocate space for columns. GridBagLayout computes
      // the number of columns based on the (row with max number of)
      // components you give it to layout.
//      gbc.gridwidth = 3;
      // The order for the insets is: [top, left, bottom, right]
//      gbc.insets = new Insets(10, 0, 0 ,0); // works okay
      // I've never had to use ipad constraints.
//      gbc.ipady = 20;
      gbc.weightx = 1.0;
      gbc.anchor = GridBagConstraints.WEST;
      jp.add(encStrTF, gbc);
 
      gbc.gridx = 0;
      gbc.gridy = 1;
      // This component will span both columns.
      gbc.gridwidth = 2;
      gbc.anchor = GridBagConstraints.CENTER;
      gbc.insets = new Insets(1,1,1,1);
      jp.add(jb, gbc);
 
      // Wrap jp in a scrollPane to allow the textField
      // to expand beyond the parents (jp) current size.
      scrollPane = new JScrollPane(jp);
      return scrollPane;
   }
 
   public void actionPerformed(ActionEvent ae) {
      Object obj = ae.getSource();
      System.out.println("got ae: " + ae.paramString());
   }
 
   public static void main(String[] args) {
      new B64Rx();
   }
}