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displaying one at a time

Posted on 2004-04-03
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Last Modified: 2010-05-18
hi, i wrote a simple program that contains a button and a jtextarea

when i click on the button, it will do the following...
jtextarea.append("a\n");        //statement a
jtextarea.append("b\n");        //statement b
jtextarea.append("c\n");        //statement c

wat i reli want is that...it shows statement a on the jtextarea first...after a few seconds, statement b....a few more seconds, statement c

i tried using this.sleep(1000), but it will just hang for a few seconds and then finally display everything at once

how do i display those statements once at a time? i'm using actionPerformed() for the button, is this correct?


thx,
gildan2020
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Question by:gildan2020
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Accepted Solution

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GrandSchtroumpf earned 200 total points
ID: 10747499
You need to do the append in a new thread:

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

public class MyClass extends JPanel implements ActionListener {

  JTextArea myJTextArea = new JTextArea();
  JButton myJButton = new JButton("Click Me");

  // Constructor
  public MyClass() {
    this.setLayout(new BorderLayout());
    this.add(myJButton, BorderLayout.NORTH);
    this.add(myJTextArea, BorderLayout.CENTER);
    myJButton.addActionListener(this);
  }

  // ActionListener implementation
  public void actionPerformed(ActionEvent ae) {
    System.out.println("+++  Action Performed  +++");
    Thread appendThread = new Thread() {
      public void run() {
        try {
          myJTextArea.append("a\n");        //statement a
          sleep(1000);
          myJTextArea.append("b\n");        //statement b
          sleep(1000);
          myJTextArea.append("c\n");        //statement c
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    };
    appendThread.start();
  }

  private static final String FRAME_TITLE = "My Class";
  private static final int FRAME_WIDTH  = 500;
  private static final int FRAME_HEIGHT = 300;

  public void showFrame() {
    JFrame myFrame = new JFrame(FRAME_TITLE) {
      protected void processWindowEvent(WindowEvent e) {
        super.processWindowEvent(e);
        if (e.getID() == WindowEvent.WINDOW_CLOSING) { System.exit(0); }
      }
    };
    myFrame.getContentPane().add(this, BorderLayout.CENTER);
    myFrame.pack();
    myFrame.setSize(new Dimension(FRAME_WIDTH, FRAME_HEIGHT));
    myFrame.setVisible(true);
  }

  public static void main(String[] args) {
    MyClass myMyClass = new MyClass();
    myMyClass.showFrame();
  }

}
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Author Comment

by:gildan2020
ID: 10747575
thanks a lot
that's exactly wat i wanted
:-)

gildan2020
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LVL 30

Expert Comment

by:GrandSchtroumpf
ID: 10747849
:°)
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