Adding ScrollPane to JTextArea

问题

I am working on a project for my college course. I was just wondering if anyone knew how to add a scrollBar to a JTextArea. At present I have the GUI laid out correctly, the only thing missing is the scroll bar.

This is what the GUI looks like. As you can see on the second TextArea I would like to add the Scrollbar.

This is my code where I create the pane. But nothing seems to happen... t2 is the JTextArea I want to add it to.

scroll = new JScrollPane(t2);     scroll.setBounds(10,60,780,500);     scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

Any help would be great, thanks!

回答1:

The Scroll Bar comes when your text goes beyond the bounds of your view area. Don't use Absolute Positioning, for such a small talk at hand, always prefer Layout Managers, do read the first para of the first link, to know the advantage of using a Layout Manager.

What you simply need to do is use this thingy :

JTextArea msgArea = new JTextArea(10, 10); msgArea.setWrapStyleWord(true); msgArea.setLineWrap(true);        JScrollPane msgScroller = new JScrollPane();         msgScroller.setBorder(     BorderFactory.createTitledBorder("Messages")); msgScroller.setViewportView(msgArea);  panelObject.add(msgScroller);

Here is a small program for your understanding :

import java.awt.*; import java.awt.event.*; import javax.swing.*;  public class JTextAreaScroller {     private JTextArea msgArea;     private JScrollPane msgScroller;     private JTextArea logArea;     private JScrollPane logScroller;     private JButton sendButton;     private JButton terminateButton;     private Timer timer;     private int counter = 0;     private String[] messages = {                                     "Hello there\n",                                     "How you doing ?\n",                                     "This is a very long text that might won't fit in a single line :-)\n",                                     "Okay just to occupy more space, it's another line.\n",                                     "Don't read too much of the messages, instead work on the solution.\n",                                     "Byee byee :-)\n",                                     "Cheers\n"                                 };      private ActionListener timerAction = new ActionListener()     {         @Override         public void actionPerformed(ActionEvent ae)         {             if (counter < messages.length)                 msgArea.append(messages[counter++]);             else                 counter = 0;         }     };      private void displayGUI()     {         JFrame frame = new JFrame("Chat Messenger Dummy");         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);          JPanel contentPane = new JPanel();         contentPane.setLayout(new BorderLayout(5, 5));          JPanel centerPanel = new JPanel();         centerPanel.setLayout(new GridLayout(0, 1, 5, 5));          logArea = new JTextArea(10, 10);         logArea.setWrapStyleWord(true);         logArea.setLineWrap(true);                logScroller = new JScrollPane();                 logScroller.setBorder(             BorderFactory.createTitledBorder("Chat Log"));         logScroller.setViewportView(logArea);          msgArea = new JTextArea(10, 10);         msgArea.setWrapStyleWord(true);         msgArea.setLineWrap(true);                msgScroller = new JScrollPane();                 msgScroller.setBorder(             BorderFactory.createTitledBorder("Messages"));         msgScroller.setViewportView(msgArea);          centerPanel.add(logScroller);         centerPanel.add(msgScroller);          JPanel bottomPanel = new JPanel();          terminateButton = new JButton("Terminate Session");         terminateButton.addActionListener(new ActionListener()         {             @Override             public void actionPerformed(ActionEvent ae)             {                 if (timer.isRunning())                     timer.stop();                 else                     timer.start();             }         });         sendButton = new JButton("Send");          bottomPanel.add(terminateButton);         bottomPanel.add(sendButton);          contentPane.add(centerPanel, BorderLayout.CENTER);         contentPane.add(bottomPanel, BorderLayout.PAGE_END);          frame.setContentPane(contentPane);         frame.pack();         frame.setLocationByPlatform(true);         frame.setVisible(true);          timer = new Timer(1000, timerAction);         timer.start();     }      public static void main(String... args)     {         EventQueue.invokeLater(new Runnable()         {             @Override             public void run()             {                 new JTextAreaScroller().displayGUI();             }         });     } }

Here is the outcome of the same :