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6.applet programming in java
The document discusses applet programming in Java. It defines an applet as an interactive panel embedded in a web page that can be run from a browser. Applets have a life cycle of init(), start(), stop(), and destroy() methods. The paint() method is used for any drawing or painting beyond standard GUI components. Repaint() requests a repaint but does not guarantee it. Example code demonstrates basic graphics methods and includes an applet example with supporting HTML. Advantages of applets include cross-platform capability and security sandboxing, while disadvantages are needing the Java plugin and slower initial startup.
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6.applet programming in java
- 1. APPLET PROGRAMMING IN JAVA BCA 5th sem DEEPAK SHARMA 12KSSB6031
- 2. APPLET • Anapplet is a Panel that allows interaction with a Java program • A applet is typically embedded in a Web page and can be run from a browser • You need special HTML in the Web page to tell the browser about the applet • For security reasons, applets run in a sandbox: they have no access to the client’s file system • Most modern browsers support Java 1.4 if they have the appropriate plug-in • A programmer should be able to write applets that can run on any browser
- 3. Applet Life Cycle Born Running Idle Dead Begin init() stop() paint() start() destroy() End
- 4. Applets have 4life cycle methods. They are: init() – It is called to initialize the applet before it gets loaded start() – It is called to provide start up behavior stop() – Called to stop any operations which are started using start() method. destroy() – Is called when an applet has finished execution.
- 5. init() start() dosome work stop() destroy() ‘init’ and ‘destroy’ are only called once each ‘start’ and ‘stop’ are called whenever the browser enters and leaves the page ‘do some work’ is code called by your listeners ‘paint’ is called when the applet needs to be repainted
- 6. public void paint(Graphicsg) • Needed if you do any drawing or painting other than just using standard GUI Components. • Any painting you want to do should be done here, or in a method you call from here. • Painting that you do in other methods may or may not happen. • Never call paint(Graphics), call repaint( ).
- 7. Repaint() Call repaint() when you have changed something and want your changes to show up on the screen repaint( ) is a request--it might not happen When you call repaint( ), Java schedules a call to update(Graphics g)
- 8. Example Graphics Methods g.drawString(“Hello”, 20, 20); Hello g.drawRect(x, y, width, height); g.fillRect(x, y, width, height); g.drawOval(x, y, width, height); g.fillOval(x, y, width, height); g.setColor(Color.red);
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- 10. Html Code ForApplet <html> <body> <applet code="ball1.class" width=200 height=200> </applet> </body> </html>
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- 13. Applet ADVANTAGES Applets are cross platform and can run on Windows, Mac OS and Linux platform Applets can work on all the versions of Java Plug-in. Applet runs in a sandbox, so the user doesn’t need to trust the code and it can work without security approval. DISADVANTAGES: Java Plug-in is required to run applet. Java applet needs JVM so first time it takes significant start-up time. Difficult to design and build good user interface in applets compared to other technologies.
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