Event Handling

Liste von Event-Konstanten mit zugehörigen Komponenten

`EventObject`	ID	Klasse
`ActionEvent`	`ACTION_PERFORMED`	`Button`, `List`, `Checkbox`,`MenuItem`, `TextField`
`FocusEvent`	`FOCUS_GAINED`	`Component`
	`FOCUS_LOST`
`KeyEvent`	`KEY_PRESSED`
	`KEY_RELEASED`
	`KEY_TYPED`
`MouseEvent`	`MOUSE_ENTERED`
	`MOUSE_EXITED`
	`MOUSE_PRESSED`
	`MOUSE_RELEASED`
	`MOUSE_MOVED`
	`MOUSE_DRAGGED`
`ComponentEvent`	`COMPONENT_HIDDEN`
	`COMPONENT_SHOWN`
	`COMPONENT_MOVED`
	`COMPONENT_RESIZED`
`ContainerEvent`	`COMPONENT_ADDED`	`Container`
	`COMPONENT_REMOVED`
`ItemEvent`	`SELECTED`	`List`, `Choice`, `Checkbox`
	`DESELECTED`	`CheckboxMenuItem`
	`ITEM_STATE_CHANGED`
`AdjustmentEvent`	`TRACK`	`Scrollbar`
	`UNIT_INCREMENT`
	`UNIT_DECREMENT`
	`BLOCK_INCREMENT`
	`BLOCK_DECREMENT`
`WindowEvent`	`WINDOW_ACTIVATED`	`Window`, `Frame`, `Dialog`
	`WINDOW_DEACTIVATED`
	`WINDOW_OPENED`
	`WINDOW_CLOSED`
	`WINDOW_ICONIFIED`
	`WINDOW_DEICONIFIED`
	`WINDOW_CLOSING`
`TextEvent`	`TEXT_VALUE_CHANGED`	`TextComponent`

Funktionsweise des Event Handling:

Bem: java.awt.Component vererbt u.a. addMouseListener
         vergleiche hierzu Java 2 PLatform Specification java.awt / Component

  import java.applet.Applet;
  import java.awt.*;
  import java.awt.event.*;
  
  public class MouseListenerDemo extends Applet
                                 implements MouseListener {    
  
    public void init() {
      setBackground(Color.blue);
      addMouseListener(this);
    }
  
    public void mouseClicked(MouseEvent e) {
      getAppletContext().showStatus(
               "click at x:"+e.getX()+" y:"+e.getY());
    }
    public void mousePressed(MouseEvent e) {}
    public void mouseReleased(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
  }

Ein solches Applet würde wie folgt aussehen:

vergleiche hierzu Java 2 PLatform Specification 
    java.awt.event / MouseEvent

Ein anderes Beispiel: 

  hier ActionListener anstatt MouseListener

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

public class ActionApplet extends Applet 
                           implements ActionListener {
private Button b;

  public ActionFrame() {
    b = new Button("Java");
    b.addActionListener(this);
    add("Center",b);
  }

  public void actionPerformed(ActionEvent e) {
    System.out.println("Action in Button Java");
  }
}