User Interfaces II GUI – Awt, Swing, Web

1. User Interfaces IIGUI – Awt, Swing, Web (c) IDMS/SQL News http://www.geocities.com/idmssql

2. User Interfaces - recap • In Java one can create at least 3 types of programs Applet Servlet/JSP Windows Java Class GUI - Introduction (c)http://www.geocities.com/idmssql

3. 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 (c)http://www.geocities.com/idmssql

4. Top Level GUI • 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 (c)http://www.geocities.com/idmssql

5. 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 (c)http://www.geocities.com/idmssql

6. 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 (c)http://www.geocities.com/idmssql

7. Sample Methods ... • Paint(), setFont(), setSize() ... • setLayout() • setBoarder(), setToolTipText(), setOpaque() ... the list is endless... GUI - Introduction (c)http://www.geocities.com/idmssql

8. 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 (c)http://www.geocities.com/idmssql

9. 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 (c)http://www.geocities.com/idmssql

10. GUI .. note ... • 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 (c)http://www.geocities.com/idmssql

11. 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 (c)http://www.geocities.com/idmssql

12. 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 (c)http://www.geocities.com/idmssql