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User Interfaces II
GUI – Awt, Swing, Web
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User Interfaces - recap
 In Java one can create at least 3 types of
programs
Windows
Applet
Servlet/JSP
Java Class
GUI - Introduction
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Graphical User Interface
 Started with AWT – Abstract Windowing Toolkit
 Later came Swing
 Today AWT components are included in Swing
 AWT components are called heavyweight
 Swing components are called lightweight
 Gui is based on events which are generated by
things like mouse, button, list selections, window
close operations, menu pulldowns, etc
GUI - Introduction
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Top Level GUI
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Swing Containers – Top Level
- JFrame
- JDialog
-JApplet
All three support some common methods
like setMenuBar(), getContentPane()
‘J’ stands for components in Swing...
Without ‘J’ they are usually part of AWT
GUI - Introduction
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GUI Jargons
 One of the negative(!) things about new
technology is the overuse of common words
and known technical words in a totally
different sense!
 So we hear terms like component, container,
layout, listener, Frame, Panel, Window,
Dialog ... a never ending list
 We have to live with this!!!
GUI - Introduction
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GUI Objects – at lower level
 GUI is based on 3 types of objects
 Containers
- JPanel, JScrollPane etc
 Selectors
- JButton, JTextField, JCheckBox etc
 Info Display
JTextArea, JTable etc (editable)
JLabel, JProgressBar etc (non-editable)
GUI - Introduction
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Sample Methods ...
 Paint(), setFont(), setSize() ...
 setLayout()
 setBoarder(), setToolTipText(), setOpaque()
... the list is endless...
GUI - Introduction
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Example : GuiSample1
import java.awt.*;
import javax.swing.*; // Packages used
import java.awt.event.*;
public class GuiSample1 extends JFrame {
JButton myButton = new JButton("Press Here");
JTextArea myArea = new JTextArea(10,20);
public void setupGUI() {
setTitle("S212 - Java Crash Course");
myButton.setEnabled(true);
Container c = getContentPane();
c.setLayout(new FlowLayout());
c.add(myButton);
c.add(myArea);
setSize(400,300); }
See next Page
GUI - Introduction
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Gui Code continued...
// we need a main to instantiate and execute this class
public static void main(String args[]) {
GuiSample1 dec18 = new GuiSample1();
dec18.setupGUI();
dec18.setVisible(true);
dec18.myArea.setEditable(false);
// Quit the application when the user 'closes' the Window
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);}
});
}//main
} //
The above code does very little, but is complete.
GUI - Introduction
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GUI .. note ...
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The class extends JFrame
Container is created by getContentPane()
setLayout method is used
Buttons etc added by add(...) command
Main () gets controll first
Main instantiate a new object ‘dec18’
Method setupGUI does the housekeeping...
We utilize a standard ‘WindowsListener’
mechanism to close.
A complete example is given as GuiSample1.java
GUI - Introduction
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Applet
 Applets are Java classes run from WWW
 Applets do not have main method
 Html file will have tags like <applet
code=“Hello5.class" width=”400"
height=”325"></applet>
 More on applets later ...
 Sample Java code follows
GUI - Introduction
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Applet sample code
/*Applet program hello5.java*/
import java.applet.Applet;
import java.awt.*;
public class Hello5 extends Applet {
public void paint(Graphics screen) {
screen.drawString("Hello World",50,25);
screen.drawRoundRect(20, 40, 100, 100, 30,10);
}//end paint()
} //End hello5 class.
GUI - Introduction
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