调整JTextArea的大小后如何调整JScrollPane的大小

Question

My JFrame Consists of three main parts a banner at top scrollpane containing a JTextArea center and a JTextField at the bottom. When I re-size the frame I adjust the columns and rows in my JTextArea. When making the frame larger the JTextArea expands visually but removes the scroll-bar. Then if I make the frame smaller the JTextArea stays the same size. This Is where I attempt to re-size my JTextArea.

    frame.addComponentListener(new ComponentAdapter() {//Waits for window to be resized by user
        public void componentResized(ComponentEvent e) {
            uneditTextArea.setRows(((int)((frame.getHeight()-140)/18.8)));//sets Textarea size based on window size
            uneditTextArea.setColumns(((int)((frame.getWidth()-100)/10.8)));
            frame.revalidate();//refreshes screen

            }
        });

Why would the ScrollPane not re adjust to the change in size of the TextField. The Rest of the code is below in case it is needed.

  public class window extends JFrame  
 {      
  private static JFrame frame = new JFrame("Lillian");      
  private static JButton inputButton = new JButton("Send");
  private static JTextField editTextArea = new JTextField(46);
  private static JTextArea uneditTextArea = new JTextArea(26,50);


  private static JPanel logoPanel = new JPanel();//Input text window
  private static JPanel itextPanel = new JPanel();//Input text window
  private static JPanel submitPanel = new JPanel();//Submit Button
  private static JPanel bottom = new JPanel();//will contain scrollpane
  private static JPanel middle = new JPanel();//willcontain itextpanel & submitbutton
  private static JPanel otextPanel = new JPanel();//Text Output
public static void runWindow() 
   { 
    ImageIcon logo = new ImageIcon("Lillian_resize.png");//banner
    ImageIcon icon = new ImageIcon("Lillian_icon.png");//application icon

    frame.setIconImage(icon.getImage());
    frame.setSize(660,640);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    
    frame.setVisible(true);

    logoPanel.setSize(10,10);
    JLabel logoLabel = new JLabel(logo);

    final JScrollPane  scrollPane = new JScrollPane(otextPanel);//adds text to panel will scrollbar    
    scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);//scrollbar only apears when more text than screen      
    scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);//scrollbar never apears 
    scrollPane.setBorder(BorderFactory.createEmptyBorder());    

    logoPanel.add(logoLabel);
    submitPanel.add(inputButton);
    itextPanel.add(editTextArea);
    otextPanel.add(uneditTextArea); 

    frame.getContentPane().add(logoPanel,"North");
    frame.getContentPane().add(middle);
    frame.getContentPane().add(bottom,"South");

    middle.add(scrollPane,"North");//adds panels to outer panel
    bottom.add(itextPanel, "West");
    bottom.add(submitPanel, "East");

    uneditTextArea.setLineWrap(true);
    uneditTextArea.setWrapStyleWord(true);          
    uneditTextArea.setEditable(false);
    uneditTextArea.setCaretPosition(uneditTextArea.getDocument().getLength());

    frame.revalidate();//refreshes screen
//---------------wait for action------------

    frame.addComponentListener(new ComponentAdapter() {//Waits for window to be resized by user
        public void componentResized(ComponentEvent e) {
            uneditTextArea.setRows(((int)((frame.getHeight()-140)/18.8)));//sets Textarea size based on window size
            uneditTextArea.setColumns(((int)((frame.getWidth()-100)/10.8)));
            frame.revalidate();//refreshes screen

            }
        });

   }
 }

Answer 1

There should be no need to use a ComponentListener to resize components. That is the job of the layout managers that you use to dynamically resize the components.

You should not be adding the text area to a JPanel first. Instead when using text areas you would generally add the text area directly to the viewport of a JScrollPane by using code like:

JScrollPane scrollPane = new JScrollPane( textArea );

Then you add the scrollpane to the frame with code like:

frame.add(scrollPane, BorderLayout.CENTER);

As you have noticed you should also NOT use hardcoded literals like "Center". Instead use the variables provided by the layout manager. Since you are using a BorderLayout, use the variables defined in the BorderLayout class.

Also, you should NOT be using static variable to create your GUI. I suggest you read the section from the Swing tutorial on Layout Manager . The tutorial will give you more information and the example code will show you how to better structure your program so that you don't need to use static variables.