To draw the applet's representation within a browser page, you use the
paint
method.For example, the
Simple
applet defines its onscreen appearance by overriding thepaint
method:public void paint(Graphics g) { //Draw a Rectangle around the applet's display area. g.drawRect(0, 0, getWidth() - 1, getHeight() - 1); //Draw the current string inside the rectangle. g.drawString(buffer.toString(), 5, 15); }Applets inherit the
paint
method from the Abstract Window Toolkit (AWT)Container
class.
Applets inherit a group of event-handling methods from the
Container
class.The
Container
class defines several methods, such asprocessKeyEvent
andprocessMouseEvent
, for handling particular types of events, and then one catch-all method calledprocessEvent
.To react to an event, an applet must override the appropriate event-specific method. For example, the following program,
SimpleClick
, implements aMouseListener
and overrides themouseClicked
method.Below is the resulting applet. When you click within its rectangle, it displays the word "click!..."./* * Java(TM) SE 6 version. */ import java.awt.event.MouseListener; import java.awt.event.MouseEvent; import java.applet.Applet; import java.awt.Graphics; //No need to extend JApplet, since we don't add any components; //we just paint. public class SimpleClick extends Applet implements MouseListener { StringBuffer buffer; public void init() { addMouseListener(this); buffer = new StringBuffer(); addItem("initializing... "); } public void start() { addItem("starting... "); } public void stop() { addItem("stopping... "); } public void destroy() { addItem("preparing for unloading..."); } void addItem(String newWord) { System.out.println(newWord); buffer.append(newWord); repaint(); } public void paint(Graphics g) { //Draw a Rectangle around the applet's display area. g.drawRect(0, 0, getWidth() - 1, getHeight() - 1); //Draw the current string inside the rectangle. g.drawString(buffer.toString(), 5, 15); } //The following empty methods could be removed //by implementing a MouseAdapter (usually done //using an inner class). public void mouseEntered(MouseEvent event) { } public void mouseExited(MouseEvent event) { } public void mousePressed(MouseEvent event) { } public void mouseReleased(MouseEvent event) { } public void mouseClicked(MouseEvent event) { addItem("click!... "); } }
Note: If you don't see the applet running above, you need to install Java Plug-in, which happens automatically when you install the Java(TM) SE JRE or JDK. This applet requires JDK 1.4 or later. You can find more information on the Java Plug-in home page.