September 22, 2003

Creating GUI widgets and using them

/*
 A simple first GUI applet that shows how to create active GUI widgets
 and use them using event-driven programming
 */

import java.awt.*;
   import java.applet.Applet;
   import java.awt.event.*;

public class FirstGUI extends Applet implements ActionListener, AdjustmentListener
{
   Button pressMe, meToo;	// there are two buttons
   Scrollbar bar;	// and a scrollbar
   
   int barValue = 0;	// this is the value of the scrollbar
   
   int pressCount = 0;	// number of times the buttons were pressed
   
   
   public void init() {
      // Create a button widget
      pressMe = new Button("PressMe");
   
      // Add it for display in the applet
      this.add(pressMe);
   
      // Register this applet as the button's lietener
      pressMe.addActionListener(this);
   
   
      // Second Button
      // Create a button widget
      meToo = new Button("Me Too!");
   
      // Add it for display in the applet
      this.add(meToo);
   
      // Register this applet as the button's lietener
      meToo.addActionListener(this);
   
   
      // Add a scrollbar
      // create the gui widget for scroll bar
      bar = new Scrollbar(Scrollbar.VERTICAL, 0, 1, 0, 100);
   
      // add it to the applet
      this.add(bar);
   
      // register a listener for it
      bar.addAdjustmentListener(this);
   
   } // init
   
      public void paint(Graphics g) {
      g.drawString("Times pressed = " + pressCount, 30, 130);
      g.drawString("Slider value = " + barValue, 30, 150);
   } // paint
   
   public void actionPerformed(ActionEvent e) {
   
      // Whe a button is pressed, this is where you have control
      System.out.println("Button was pressed.");
      pressCount = pressCount + 1;
   
      repaint();
   
   } // actionPerformed

 public void adjustmentValueChanged(AdjustmentEvent e) {
     
      System.out.println("Slider moved...");
   
      barValue = bar.getValue();
   
      repaint();
   
   } // adjustmentValueChanged
} // FirstGUI