1 applications & applets standalone applications & java applets peter mozelius dsv/ucsc
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Applications & Applets
Standalone applications & Java applets
Peter Mozelius DSV/UCSC
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Running Java Standalone applications Like traditional programs
BUT platform independent javac MyClass.java java MyClass http://java.sun.com/developer/onlineTra
ining/Programming/BasicJava1/compile.html
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Running Java on the Internet Applications could be packed as jar-
archives and executed by JNLP Run on a server
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Running Java on the Internet Two other alternatives
Servlets Running on the server side
Applets Running in the web browser
And Java Applets is the main theme for this course !!
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Inheritance for Applets An Object extended to
A Container extended to
A Panel that is extended to An Applet which I can extend to to MyApplet
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Application AppletHow to make an applet out of an
application ?
THE APPLICATION:import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
public class MyApplication extends JFrame
implements ActionListener {
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The Application private JButton northButton; private JLabel southLabel;
/** * The constructor that creates the GUI */ public MyApplication(){ //set the title and the size super("Lektion24"); setSize(300, 150);
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The Application//create some Swing components
northButton = new JButton("PUSH ME for
a greeting");
southLabel = new JLabel("Here goes the
greeting!", JLabel.CENTER);
//connect the button with a listener
northButton.addActionListener(this);
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The Application //lay out the components add(northButton, BorderLayout.NORTH); add(southLabel, BorderLayout.SOUTH);
//make the window visible and closable setVisible(true); setDefaultCloseOperation(EXIT_ON_CLOSE);
}//constructor
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The Application/** * The implementation of the method from the * interface ActionListener. The code that’s * going to be executed when the user clicks * on the button */ public void actionPerformed(ActionEvent e) { southLabel.setText("Hello Colombo!"); }//actionPerformed
public static void main(String[] args) { new MyApplication();}
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Workshop Pause
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The Applet run by AppletViewer
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The Applet Code part 1 Even simpler than the application
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
import java.applet.*;
public class MyApplet extends JApplet
implements ActionListener {
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The Applet Code part 2 private JButton northButton; private JLabel southLabel;
/** * A method that initiates the applet and * creates the GUI */ public void init(){ //set the size of the window setSize(300, 150);
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The Applet Code part 3 northButton = new JButton("PUSH ME for a greeting");
southLabel = new JLabel("Here goes the greeting!", JLabel.CENTER);
//connect the button with a listener northButton.addActionListener(this);
add(northButton, BorderLayout.NORTH); add(southLabel, BorderLayout.SOUTH);}//constructor
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The Applet Code part 4 /** * The implementation of the method from * ActionListener. The code that is * going to be executed when the user * clicks on the button */ public void actionPerformed(ActionEvent e) { southLabel.setText("Hello Colombo!"); }//actionPerformed
}//MyApplet
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The (oversimplified) HTML file<html>
<applet code="MyApplet.class" width="300" height="200"> Problems with the applet </applet>
</html>
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Workshop Pause
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Another Simple Applet A simple but illustrative Applet
Run with the AppletViewer
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The Simple Applet Code 1import java.applet.Applet;
import java.awt.Graphics;
import java.awt.Color;
public class SimpleApplet
extends Applet{
private String text;
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The Simple Applet Code 2 public void init() { text = "I'm a simple applet"; setBackground(Color.cyan); }
public void start() { System.out.println("starting...");
}
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The Simple Applet Code 3 public void stop() {
System.out.println("stopping..."); }
public void destroy() {
System.out.println("preparing to
unload...");
}
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The Simple Applet Code 4 public void paint(Graphics g){
g.setColor(Color.blue);
g.drawRect(0, 0, getSize().width
-1, getSize().height -1);
g.setColor(Color.red);
g.drawString(text, 15, 25);
}//paint
}//SimpleApplet
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The Simple Applet Code 5 Further info about this applet can be
found on: http://java.sun.com/developer/onlineTraining/Programming/BasicJava1/applet.html#struct
In Swing applets you replace paint()
with the newer paintComponent()
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The Appletviewer How to run applets outside a web browser
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The Appletviewer The final result in a web browser A web browser works with a cache Appletviewer during the
development of the applet
That all for now, thank you!
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