Lesson Three - AllEventsApplet

The APPLET Tag

   <APPLET code="AllEventsApplet.class" width=1 height=1></APPLET>

Program Listing

The Applet

// This applet was written by Jeffrey Juliano (jjuliano@cs.buffalo.edu)

import java.applet.Applet;
import java.awt.Frame;

public class AllEventsApplet extends Applet
{
  public void init()
  {
    components = new AllEvents ("Component Demo");
  }

  public void start()
  {
    components.pack();
    components.show();
  }
  
  public void stop()
  {
    components.hide();
  }
  
  
  protected AllComponents components;
}

AllEvents

// This example was modified by Jeffrey Juliano (jjuliano@cs.buffalo.edu)
// to derrive from Frame instead of Applet.
//
// This example is from the book _Java in a Nutshell_ by David Flanagan.
// Written by David Flanagan.  Copyright (c) 1996 O'Reilly & Associates.
// You may study, use, modify, and distribute this example for any purpose.
// This example is provided WITHOUT WARRANTY either expressed or implied.

import java.awt.*;

public class AllEvents extends AllComponents {
    public AllEvents(String title) {
        super(title);
    }
    // This method handles all the events generated by all the components.
    public boolean handleEvent(Event event) {
        switch(event.id) {
        // Most components generate ACTION_EVENT
        // We test the target field to find out which component.
        case Event.ACTION_EVENT:
            if (event.target == textfield) {
                textarea.setText("Your name is: " + (String)event.arg + "\n");
            }
            else if (event.target == choice) {
                textarea.setText("Your favorite color is: " + 
                         (String) event.arg + "\n");
            }
            else if ((event.target == checkboxes[0]) ||
                 (event.target == checkboxes[1]) ||
                 (event.target == checkboxes[2])) {
                textarea.setText("Your favorite flavor is: " + 
                         checkbox_group.getCurrent().getLabel() + "\n");
            }
            else if (event.target == list) {
                textarea.setText("You double-clicked on: " + 
                         (String)event.arg + "\n");
            }
            else if (event.target == okay) {
                textarea.setText("Okay button clicked.\n");
            }
            else if (event.target == cancel) {
                textarea.setText("Cancel button clicked.\n");
            }
            else if (event.target instanceof MenuItem) {
                // Since we didn't save references to each of the menu objects,
                // we check which one was pressed by comparing labels.
                // Note that we respond to these menu items by 
                // popping up dialog boxes.
                if (((String)event.arg).equals("Quit")) {
                    YesNoDialog d = new ReallyQuitDialog(this, textarea);
                    d.show();
                }
                else if (((String)event.arg).equals("Open")) {
                    textarea.setText("You selected Open.\n");
                    // Use the dialog box created by our superclass.
                    file_dialog.pack();  // bug workaround
                    file_dialog.show();  // blocks until user selects a file
                    textarea.setText("You selected file: " + 
                             file_dialog.getFile());
                }
                else if (((String)event.arg).equals("About")) {
                    InfoDialog d;
                    d = new InfoDialog(this, "About AWT Demo",
                               "This demo was written by David Flanagan\n" +
                               "Copyright (c) 1996 O'Reilly & Associates");
                    d.show();
                    textarea.setText("You selected About.\n");
                }
            }
            else {
                textarea.setText("Unknown action event.");
            }
            break;
            
        // Double-clicking on a list generates an action event.
        // But list selection and deselection are separate event types.
        case Event.LIST_SELECT:
            textarea.setText("You selected: " + 
                     list.getItem(((Integer)event.arg).intValue()) + "\n");
            break;
        case Event.LIST_DESELECT:
            textarea.setText("You deselected: " + 
                     list.getItem(((Integer)event.arg).intValue()) + "\n");
            break;
            
        // These are some events pertaining to the window itself.
        case Event.WINDOW_DESTROY:
            textarea.setText("Window Destroy\n");
            break;
        case Event.WINDOW_ICONIFY:
            textarea.setText("Window iconify\n");
            break;
        case Event.WINDOW_DEICONIFY:
            textarea.setText("Window deiconify\n");
            break;
        case Event.WINDOW_MOVED:
            textarea.setText("Window moved\n");
            break;
            
        // We print a message about each of these mouse and key events,
        // but return false after so that they can still
        // be properly handled by their correct recipient.
        case Event.MOUSE_DOWN:
            textarea.setText("Mouse down: [" + event.x + "," + event.y + "]\n");
            return false;
        case Event.MOUSE_UP:
            textarea.setText("Mouse up: [" + event.x + "," + event.y + "]\n");
            return false;
        case Event.MOUSE_DRAG:
            textarea.setText("Mouse drag: [" + event.x + "," + event.y + "]\n");
            return false;
        case Event.KEY_PRESS:
        case Event.KEY_ACTION:
            textarea.setText("Key press\n");
            return false;
        case Event.KEY_RELEASE:
        case Event.KEY_ACTION_RELEASE:
            textarea.setText("Key release\n");
            return false;
            
        // We ignore these event types.
        case Event.GOT_FOCUS:
        case Event.LOST_FOCUS:
        case Event.MOUSE_ENTER:
        case Event.MOUSE_EXIT:
        case Event.MOUSE_MOVE:
            return false;
            
        // We shouldn't ever get this...
        default:
            textarea.setText("Unexpected Event type: " + event + "\n");
            break;
        }
        return true;
    }

    // Here's the method that lets us run and test this class.
    public static void main(String[] args) {
        Frame f = new AllEvents("AWT Demo");
        f.pack();
        f.show();
    }
}