Gui
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This document discusses the evolution of graphical user interface (GUI) capabilities in the Java programming language. It describes the Abstract Window Toolkit (AWT) introduced in JDK 1.0, which provided basic cross-platform GUI functionality but had limitations. JDK 1.1 improved on AWT with an event delegation model. JDK 1.2 introduced Swing, a richer GUI library that better integrated with native operating system look and feels. Swing components are lightweight compared to heavyweight AWT components. The document also covers GUI component classes, layout managers, menus, labels and event handling in Java GUI programming.
![A
simple
example
//Demonstrates construction of a Container and a Button
import java.awt.*;
class Gui extends Frame
{
public Gui(String s) //constructor
{ super(s); //construct Frame part of Gui
setBackground(Color.yellow);
setLayout(new FlowLayout());
Button pushButton = new Button("press me");
add(pushButton);
}
} //class Gui
class Ex_1 //Creates an instance of class Gui
{ public static void main(String[] args)
{ Gui screen = new Gui("Example 1");
screen.setSize(500,100);
screen.setVisible(true);
}
} //class Ex_1](https://image.slidesharecdn.com/gui-140914051714-phpapp02/85/Gui-11-320.jpg)
![31 italic.addItemListener( handler );
32
33 addWindowListener(
34 new WindowAdapter() {
35 public void windowClosing( WindowEvent e )
36 {
37 System.exit( 0 );
38 }
39 }
40 );
41
42 setSize( 275, 100 );
43 show();
44 }
45
46 public static void main( String args[] )
47 {
48 new CheckBoxTest();
49 }
50
51 private class CheckBoxHandler implements ItemListener {
52 private int valBold = Font.PLAIN;
53 private int valItalic = Font.PLAIN;
54
55 public void itemStateChanged( ItemEvent e )
56 {
57 if ( e.getSource() == bold )
58 if ( e.getStateChange() == ItemEvent.SELECTED )
59 valBold = Font.BOLD;
60 else
61 valBold = Font.PLAIN;
Because CheckBoxHandler implements
ItemListener, it must define method
itemStateChanged
getStateChange returns
ItemEvent.SELECTED or
ItemEvent.DESELECTED](https://image.slidesharecdn.com/gui-140914051714-phpapp02/85/Gui-26-320.jpg)
![30 // create a list with the items in the colorNames array
31 colorList = new JList( colorNames );
32 colorList.setVisibleRowCount( 5 );
33
34 // do not allow multiple selections
35 colorList.setSelectionMode(
36 ListSelectionModel.SINGLE_SELECTION );
37
38 // add a JScrollPane containing the JList
39 // to the content pane
40 c.add( new JScrollPane( colorList ) );
41
42 // set up event handler
43 colorList.addListSelectionListener(
44 new ListSelectionListener() {
45 public void valueChanged( ListSelectionEvent e )
46 {
47 c.setBackground(
48 colors[ colorList.getSelectedIndex() ] );
49 }
50 }
51 );
52
53 setSize( 350, 150 );
54 show();
55 }
56
57 public static void main( String args[] )
58 {
59 ListTest app = new ListTest();
Initialize JList with array of
Strings, and show 5 items at
a time.
Make the JList a single-selection
list.
Create a new JScrollPane
object, initialize it with a JList,
and attach it to the content pane.
Change the color according to the item
selected (use getSelectedIndex).](https://image.slidesharecdn.com/gui-140914051714-phpapp02/85/Gui-32-320.jpg)
![1 // Fig. 12.20: MouseDetails.java
2 // Demonstrating mouse clicks and
3 // distinguishing between mouse buttons.
4 import javax.swing.*;
5 import java.awt.*;
6 import java.awt.event.*;
7
8 public class MouseDetails extends JFrame {
9 private String s = "";
10 private int xPos, yPos;
11
12 public MouseDetails()
13 {
14 super( "Mouse clicks and buttons" );
15
16 addMouseListener( new MouseClickHandler() );
17
18 setSize( 350, 150 );
19 show();
20 }
21
22 public void paint( Graphics g )
23 {
24 g.drawString( "Clicked @ [" + xPos + ", " + yPos + "]",
25 xPos, yPos );
26 }
27
Another example, illustrating
mouse events in AWT and Swing
Add a listener for a
mouse click.](https://image.slidesharecdn.com/gui-140914051714-phpapp02/85/Gui-33-320.jpg)
![28 public static void main( String args[] )
29 {
30 MouseDetails app = new MouseDetails();
31
32 app.addWindowListener(
33 new WindowAdapter() {
34 public void windowClosing( WindowEvent e )
35 {
36 System.exit( 0 );
37 }
38 }
39 );
40 }
41
42 // inner class to handle mouse events
43 private class MouseClickHandler extends MouseAdapter {
44 public void mouseClicked( MouseEvent e )
45 {
46 xPos = e.getX();
47 yPos = e.getY();
48
49 String s =
50 "Clicked " + e.getClickCount() + " time(s)";
51
52 if ( e.isMetaDown() ) // Right mouse button
53 s += " with right mouse button";
54 else if ( e.isAltDown() ) // Middle mouse button
55 s += " with center mouse button";
56 else // Left mouse button
57 s += " with left mouse button";
58
Use a named inner class as the event handler. Can still
inherit from MouseAdapter (extends MouseAdapter).
Use getClickCount, isAltDown,
and isMetaDown to determine the
String to use.](https://image.slidesharecdn.com/gui-140914051714-phpapp02/85/Gui-34-320.jpg)
Gui
- 1. GUI in Java AWT and Swing • Most GUI class libraries in C++ are pla=orm specific – Different hardware capabiliCes – Subtle differences between the "look-‐and-‐feel" of various Windowing operaCng systems • Abstract Window Toolkit (AWT) is cross-‐pla=orm – Swing can observe various OS look-‐and-‐feel convenCons
- 2. JDK 1.0 (circa 1996) • JDK 1.0 went a long way to implemenCng pla=orm-‐independent GUI library • Bruce Eckel: it "produced a GUI that looks equally mediocre on all systems." – Just 4 fonts – Couldn’t access GUI of naCve OS – Didn’t separate model and UI code cleanly
- 3. JDK 1.1 (circa 1998) • JDK 1.1 makes AWT more robust and extensible • DelegaCon-‐based event model separates user interface from problem domain – Designates "listeners" of events triggered by problem domain objects – Listeners implement the Observer design paern • Other enhancements: buon tool Cps, cut/paste to the clipboard, popup menus, prinCng, etc. – Adds supports for JavaBeans
- 4. JDK 1.2 (Swing) • JDK 1.2 adds Java FoundaCon Classes – Swing is the GUI library for JDK 1.2 – Much richer class library plus beer integraCon with look and feel of GUI of OS – Eckel: "The ‘revision 3’ rule of sobware industry (a product isn’t good unCl revision 3) seems to hold true with programming languages as well."
- 5. Graphical Components button menus title bar menu bar combo box scroll bars
- 6. AWT class hierarchy Checkbox, Choice, Label, List, Scrollbar,ScrollPane, TextArea, TextField
- 8. Component and Container • Component contributes several public methods to all its subclasses: public void setSize(int width, int height); //set size in pixels public void setBackground(Color c); //see class Color for colors public void setVisible(boolean b); //Display on screen (creates peer) • Container is an abstract class: – It cannot be instanCated; subclasses must implement some methods – Container does implement some useful methods, including: public Component add(Component comp); //put a Component in a Container public setLayout(LayoutManager mgr); //lay out components in some pattern
- 9. Window and Frame classes • A Window is a top-‐level window with no borders and no menubar – It can generate a WindowOpened or a WindowClosed event, to which a WindowListener or WindowAdapter can respond • A Frame is a top-‐level window with a Ctle and a border • Because it has more features, it can generate more events: WindowOpened, WindowClosing, WindowClosed, WindowIconified, WindowDeiconified, WindowActivated, WindowDeactivated • Respond to these events with a WindowListener • Once a subclass of Container has been constructed, it can add (aach) any AWT component within it, such as a Buon, Label, TextField, or another Frame or Panel
- 10. JFrame Window
- 11. A simple example //Demonstrates construction of a Container and a Button import java.awt.*; class Gui extends Frame { public Gui(String s) //constructor { super(s); //construct Frame part of Gui setBackground(Color.yellow); setLayout(new FlowLayout()); Button pushButton = new Button("press me"); add(pushButton); } } //class Gui class Ex_1 //Creates an instance of class Gui { public static void main(String[] args) { Gui screen = new Gui("Example 1"); screen.setSize(500,100); screen.setVisible(true); } } //class Ex_1
- 12. Responding to events //Program to demonstrate action listeners and event handlers import java.awt.*; import java.awt.event.*; class Gui extends Frame implements ActionListener, WindowListener { public Gui(String s) //constructor { super(s); setBackground(Color.yellow); setLayout(new FlowLayout()); addWindowListener(this); //listen for events on this Window Button pushButton = new Button("press me"); add(pushButton); pushButton.addActionListener(this); //listen for Button press } //define action for Button press public void actionPerformed(ActionEvent event) { final char bell = 'u0007'; if (event.getActionCommand().equals("press me")) { System.out.print(bell); } } //define methods in WindowListener interface public void windowClosing(WindowEvent event) { System.exit(0); } public void windowClosed(WindowEvent event) {} //do nothing public void windowDeiconified(WindowEvent event){} public void windowIconified(WindowEvent event){} public void windowActivated(WindowEvent event){} public void windowDeactivated(WindowEvent event){} public void windowOpened(WindowEvent event){} }
- 13. Responding to events, conCnued • Uses event delegaCon model of JDK 1.1 • When an event occurs, it generates an ActionEvent object – ActionListener interface listens for a parCcular ActionEvent – Responds in its actionPerformed method • WindowListener interface observes events triggered by Window object, such as closing it, and responds in corresponding methods • Program now has a live Buon: actionPerformed method rings a bell – Also a live close window buon, which performs System.exit(0) • Most Components in the AWT have corresponding Listeners
- 14. Adapter Classes • Time consuming to define all interface methods – WindowListener has seven methods • What if we only want to use one? • Required to define all methods in interface • Adapter class implements an interface • Does anyone recognize a design paern here? • Default implementaCon ({ }, empty body) for all methods – You then extend adapter class, • overriding methods for events you care about, such as windowClosing. – Has "is a" relaConship with interface • WindowAdapter is a WindowListener • MouseAdapter is a MouseListener
- 15. Layout managers Ø JDK provides a set of generic layout manager classes FlowLayout (the default) add components one after another in rows: setLayout(new FlowLayout(FlowLayout.LEFT,10,10); for (int counter=1; counter <= 6; counter++) add(new Button(String.valueOf(counter))); 1 2 3 4 5 6 GridLayout places components in cells of a grid: setLayout(new GridLayout(3,2,5,5); //3 rows, 2 columns, 5 pixel gaps for (int counter=1; counter <= 6; counter++) add(new Button(String.valueOf(counter))); 1 2 3 4 5 6 BorderLayout arranges components using along four sides (North, South, East West) and Center positions
- 16. Swing overview • Defined in package javax.swing • Original GUI components from AWT in java.awt – Heavyweight components -‐ rely on local pla=orm's windowing system for look and feel • Swing components are lightweight – Not weighed down by GUI capabiliCes of pla=orm – More portable than heavyweight components • Swing components allow programmer to specify look and feel – Can change depending on pla=orm – Can be same across all pla=orms
- 17. Swing component inheritance hierarchy java.awt.Component java.awt.Container java.lang.Object javax.swing.JComponent • Component defines methods used in its subclasses (for example, paint and repaint) • Container - collection of related components • When using JFrame, add components to content pane (a Container) • JComponent - superclass to most Swing components
- 18. Jcomponent features • Pluggable look and feel – Can look like different pla=orms, at run-‐Cme • Shortcut keys (mnemonics) – Direct access to components through keyboard • Common event handling – If several components perform same acCons • Tool Cps – Describe component when mouse rolls over it
- 19. Menus Menu Bar – JMenuBar() – add( JMenu ) Menu – JMenu( String ) – add( JMenuItem ) JMenuItem( String ) JMenuItem( String,int ) JMenuBar mb = new JMenuBar(); //create a menu bar JMenu fileMenu = new JMenu (“File”); //create a menu mb.add( fileMenu ); //add menu to menu bar setMenuBar( mb ); // add a menu bar to frame fileMenu.setMnemonic( KeyEvent.VK_F ); // add a hotkey to menu JMenuItem miOpen = new JMenuItem( “Open...”, KeyEvent.VK_O ); JMenuItem miExit = new JMenuItem( “Exit” ); fileMenu.add( miOpen ); // add a menu item fileMenu.addSeparator(); // add a menu separator fileMenu.add( miExit );
- 20. JLabel • Labels – Provide text instrucCons on a GUI – Read-‐only text – Programs rarely change a label's contents – Class JLabel (subclass of JComponent) • Methods – Can declare label text in constructor – myLabel.setToolTipText( "Text" ) • Displays "Text" in a tool Cp when mouse over label – myLabel.setText( "Text" ) – myLabel.getText()
- 21. JLabel • Icon – Object that implements interface Icon – One class is ImageIcon (.gif and .jpeg images) 24 Icon bug = new ImageIcon( "bug1.gif" ); • Assumed same directory as program – Display an icon with JLabel’s setIcon method 33 label3.setIcon( bug ); • myLabel.setIcon( myIcon ); • myLabel.getIcon //returns current Icon
- 22. 1 // Fig. 12.4: LabelTest.java 2 // Demonstrating the JLabel class. 3 import javax.swing.*; 4 import java.awt.*; 5 import java.awt.event.*; 6 7 public class LabelTest extends JFrame { 8 private JLabel label1, label2, label3; 9 10 public LabelTest() 11 { 12 super( "Testing JLabel" ); 13 14 Container c = getContentPane(); 15 c.setLayout( new FlowLayout() ); 16 17 // JLabel constructor with a string argument 18 label1 = new JLabel( "Label with text" ); 19 label1.setToolTipText( "This is label1" ); 20 c.add( label1 ); 21 22 // JLabel constructor with string, Icon and 23 // alignment arguments 24 Icon bug = new ImageIcon( "bug1.gif" ); 25 label2 = new JLabel( "Label with text and icon", 26 bug, SwingConstants.LEFT ); 27 label2.setToolTipText( "This is label2" ); 28 c.add( label2 ); 29 Create a Container object, to which we attach JLabel objects (subclass of JComponent). Initialize text in JLabel constructor. Set the tool tip text, and attach component to Container c. Create a new ImageIcon (assumed to be in same directory as program). Set ImageIcon and alignment of text in JLabel constructor.
- 23. JBuon • Methods of class JButton – Constructors JButton myButton = new JButton( "Label" ); JButton myButton = new JButton( "Label", myIcon ); – setRolloverIcon( myIcon ) • Sets image to display when mouse over buon • Class ActionEvent getActionCommand • returns label of buon that generated event Icon bug1 = new ImageIcon( "bug1.gif" ); fancyButton = new JButton( "Fancy Button", bug1 ); fancyButton.setRolloverIcon( bug2 );
- 24. JCheckBox • When JCheckBox changes – ItemEvent generated • Handled by an ItemListener, which must define itemStateChanged – Register handlers with with addItemListener private class CheckBoxHandler implements ItemListener { • Class public void itemStateChanged( ItemEvent e ) ItemEvent – getStateChange • Returns ItemEvent.SELECTED or ItemEvent.DESELECTED
- 25. 1 // Fig. 12.12: CheckBoxTest.java 2 // Creating Checkbox buttons. 3 import java.awt.*; 4 import java.awt.event.*; 5 import javax.swing.*; 6 7 public class CheckBoxTest extends JFrame { 8 private JTextField t; 9 private JCheckBox bold, italic; 10 11 public CheckBoxTest() 12 { 13 super( "JCheckBox Test" ); 14 15 Container c = getContentPane(); 16 c.setLayout(new FlowLayout()); 17 18 t = new JTextField( "Watch the font style change", 20 ); 19 t.setFont( new Font( "TimesRoman", 1. import Font.PLAIN, 14 ) ); 20 c.add( t ); 21 1.1 DeclaraCons 22 // create checkbox objects 23 bold = new JCheckBox( "Bold" ); 24 c.add( bold ); 25 26 italic = new JCheckBox( "Italic" ); 27 c.add( italic ); 28 29 CheckBoxHandler handler = new CheckBoxHandler(); 30 bold.addItemListener( handler ); Create JCheckBoxes 1.2 IniCalize JCheckBoxes 1.3 Register event handler
- 26. 31 italic.addItemListener( handler ); 32 33 addWindowListener( 34 new WindowAdapter() { 35 public void windowClosing( WindowEvent e ) 36 { 37 System.exit( 0 ); 38 } 39 } 40 ); 41 42 setSize( 275, 100 ); 43 show(); 44 } 45 46 public static void main( String args[] ) 47 { 48 new CheckBoxTest(); 49 } 50 51 private class CheckBoxHandler implements ItemListener { 52 private int valBold = Font.PLAIN; 53 private int valItalic = Font.PLAIN; 54 55 public void itemStateChanged( ItemEvent e ) 56 { 57 if ( e.getSource() == bold ) 58 if ( e.getStateChange() == ItemEvent.SELECTED ) 59 valBold = Font.BOLD; 60 else 61 valBold = Font.PLAIN; Because CheckBoxHandler implements ItemListener, it must define method itemStateChanged getStateChange returns ItemEvent.SELECTED or ItemEvent.DESELECTED
- 27. JRadioButton • Radio buons – Have two states: selected and deselected – Normally appear as a group • Only one radio buon in group selected at Cme • SelecCng one buon forces the other buons off – Mutually exclusive opCons – ButtonGroup -‐ maintains logical relaConship between radio buons • Class JRadioButton – Constructor • JRadioButton( "Label", selected ) • If selected true, JRadioButton iniCally selected
- 28. 1 // Fig. 12.12: RadioButtonTest.java 2 // Creating radio buttons using ButtonGroup and JRadioButton. 3 import java.awt.*; 4 import java.awt.event.*; 5 import javax.swing.*; 6 7 public class RadioButtonTest extends JFrame { 8 private JTextField t; 9 private Font plainFont, boldFont, 10 italicFont, boldItalicFont; 11 private JRadioButton plain, bold, italic, boldItalic; 12 private ButtonGroup radioGroup; 13 14 public RadioButtonTest() 15 { 16 super( "RadioButton Test" ); 17 18 Container c = getContentPane(); 19 c.setLayout( new FlowLayout() ); 1. import 20 21 t = new JTextField( "Watch the font style change", 25 ); 22 c.add( t ); 23 24 // Create radio buttons 25 plain = new JRadioButton( "Plain", true ); 26 c.add( plain ); 27 bold = new JRadioButton( "Bold", false); 28 c.add( bold ); 29 italic = new JRadioButton( "Italic", false ); 30 c.add( italic ); Initialize radio buttons. Only one is initially selected. 1.1 DeclaraCons 1.2 IniCalizaCon
- 29. 31 boldItalic = new JRadioButton( "Bold/Italic", false ); 32 c.add( boldItalic ); 33 34 // register events 35 RadioButtonHandler handler = new RadioButtonHandler(); 36 plain.addItemListener( handler ); 37 bold.addItemListener( handler ); 38 italic.addItemListener( handler ); 39 boldItalic.addItemListener( handler ); 40 41 // create logical relationship between JRadioButtons 42 radioGroup = new ButtonGroup(); 43 radioGroup.add( plain ); 44 radioGroup.add( bold ); 45 radioGroup.add( italic ); 46 radioGroup.add( boldItalic ); 47 48 plainFont = new Font( "TimesRoman", Font.PLAIN, 14 ); 49 boldFont = new Font( "TimesRoman", Font.BOLD, 14 ); 50 italicFont = new Font( "TimesRoman", Font.ITALIC, 14 ); 51 boldItalicFont = 52 new Font( "TimesRoman", Font.BOLD + Font.ITALIC, 14 ); 53 t.setFont( plainFont ); 54 55 setSize( 300, 100 ); 56 show(); 57 } 58 Create a ButtonGroup. Only one radio button in the group may be selected at a time. Method add adds radio buttons to the ButtonGroup
- 31. JList • List – Displays series of items – may select one or more items • Class JList – Constructor JList( arrayOfNames ) • Takes array of Objects (Strings) to display in list – setVisibleRowCount( n ) • Displays n items at a Cme • Does not provide automaCc scrolling
- 32. 30 // create a list with the items in the colorNames array 31 colorList = new JList( colorNames ); 32 colorList.setVisibleRowCount( 5 ); 33 34 // do not allow multiple selections 35 colorList.setSelectionMode( 36 ListSelectionModel.SINGLE_SELECTION ); 37 38 // add a JScrollPane containing the JList 39 // to the content pane 40 c.add( new JScrollPane( colorList ) ); 41 42 // set up event handler 43 colorList.addListSelectionListener( 44 new ListSelectionListener() { 45 public void valueChanged( ListSelectionEvent e ) 46 { 47 c.setBackground( 48 colors[ colorList.getSelectedIndex() ] ); 49 } 50 } 51 ); 52 53 setSize( 350, 150 ); 54 show(); 55 } 56 57 public static void main( String args[] ) 58 { 59 ListTest app = new ListTest(); Initialize JList with array of Strings, and show 5 items at a time. Make the JList a single-selection list. Create a new JScrollPane object, initialize it with a JList, and attach it to the content pane. Change the color according to the item selected (use getSelectedIndex).
- 33. 1 // Fig. 12.20: MouseDetails.java 2 // Demonstrating mouse clicks and 3 // distinguishing between mouse buttons. 4 import javax.swing.*; 5 import java.awt.*; 6 import java.awt.event.*; 7 8 public class MouseDetails extends JFrame { 9 private String s = ""; 10 private int xPos, yPos; 11 12 public MouseDetails() 13 { 14 super( "Mouse clicks and buttons" ); 15 16 addMouseListener( new MouseClickHandler() ); 17 18 setSize( 350, 150 ); 19 show(); 20 } 21 22 public void paint( Graphics g ) 23 { 24 g.drawString( "Clicked @ [" + xPos + ", " + yPos + "]", 25 xPos, yPos ); 26 } 27 Another example, illustrating mouse events in AWT and Swing Add a listener for a mouse click.
- 34. 28 public static void main( String args[] ) 29 { 30 MouseDetails app = new MouseDetails(); 31 32 app.addWindowListener( 33 new WindowAdapter() { 34 public void windowClosing( WindowEvent e ) 35 { 36 System.exit( 0 ); 37 } 38 } 39 ); 40 } 41 42 // inner class to handle mouse events 43 private class MouseClickHandler extends MouseAdapter { 44 public void mouseClicked( MouseEvent e ) 45 { 46 xPos = e.getX(); 47 yPos = e.getY(); 48 49 String s = 50 "Clicked " + e.getClickCount() + " time(s)"; 51 52 if ( e.isMetaDown() ) // Right mouse button 53 s += " with right mouse button"; 54 else if ( e.isAltDown() ) // Middle mouse button 55 s += " with center mouse button"; 56 else // Left mouse button 57 s += " with left mouse button"; 58 Use a named inner class as the event handler. Can still inherit from MouseAdapter (extends MouseAdapter). Use getClickCount, isAltDown, and isMetaDown to determine the String to use.
- 35. 59 setTitle( s ); // set the title bar of the window 60 repaint(); 61 } Set the Frame’s title bar. 62 } 63 } Program Output
- 36. GUI Builders • Netbeans (Sun) • JBuilder (Borland) • Eclipse (IBM and others) – Visual Editor • Help à Sobware Updates à Find and Install…