awt and swings

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AWT and Swing:

AWT and Swing Most GUI class libraries in C++ are platform specific Different hardware capabilities Subtle differences between the "look-and-feel" of various Windowing operating systems Abstract Window Toolkit (AWT) is cross-platform Swing can observe various OS look-and-feel conventions

Swings in java:

Swings in java Presented by: Surendra Eid : surendra4.m@gmail.com

Common functionality/specific implementation approach:

Common functionality/specific implementation approach Toolkit -------------------------------------------------- AWT -----------|------------ Button List JVM | | Native GUI Button Peer List Peer (Windows, Mac, X) AWT GUI classes are platform-independent elements Each AWT platform-specific toolkit comes with peer class implementing platform-specific behavior of its AWT class Combining platform-independent AWT class with platform-specific peer class transforms generic, abstract windows behavior into specific, particular behavior

Peer classes at run-time:

Peer classes at run-time class TestPeer { TestPeer() { Frame myFrame = new Frame("my Frame"); //create window Frame Button myButton = new Button("my Button"); //create myButton myFrame.add("Center",myButton); //put myButton in myFrame myFrame.setVisible(true); //button appears in window on screen //setVisible() creates peer objects for myFrame & myButton ComponentPeer buttonPeer = myButton.getPeer(); //now works } } TestPeer first constructs a frame, then adds a button on the frame setVisible method creates peer objects on platform Last line now accesses myButton’s peer object Peer classes are usually hidden from developers. Why? In fact, in newer versions of JDK, getPeer() method is "deprecated" Peer classes strongly discouraged for code maintenance purposes First, create a frame. Next, create a Button. Attach (add) myButton to myFrame. Now, peer objects exist. Note: getPeer() is now “deprecated.” Set myFrame and myButton visible, by creating platform-specific peer objects.

JDK 1.0 (circa 1996):

JDK 1.0 (circa 1996) JDK 1.0 went a long way to implementing platform-independent GUI library Bruce Eckel: it "produced a GUI that looks equally mediocre on all systems." Just 4 fonts Couldn’t access GUI of native OS Didn’t separate model and UI code cleanly

JDK 1.1 (circa 1998):

JDK 1.1 (circa 1998) JDK 1.1 makes AWT more robust and extensible Delegation-based event model separates user interface from problem domain Avoids cascaded if statements testing for object type required by first AWT Designates "listeners" of events triggered by problem domain objects Listeners implement the Observer design pattern Other enhancements: button tool tips, cut/paste to the clipboard, popup menus, printing, etc. Adds supports for JavaBeans

JDK 1.2 (Swing):

JDK 1.2 (Swing) JDK 1.2 adds Java Foundation Classes Swing is the GUI library for JDK 1.2 Much richer class library plus better integration with look and feel of GUI of OS Eckel: "The ‘revision 3’ rule of software industry (a product isn’t good until revision 3) seems to hold true with programming languages as well."

Graphical Components:

Graphical Components button menus title bar menu bar combo box scroll bars

AWT class hierarchy:

AWT class hierarchy Checkbox, Choice, Label, List, Scrollbar,ScrollPane, TextArea, TextField

Component and Container:

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 instantiated; 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

Window and Frame classes:

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 title 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 (attach) any AWT component within it, such as a Button, Label, TextField, or another Frame or Panel

A simple example:

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 Superclass does not most of the work of creating an instance of Gui. Modify properties of Gui. Create a button and attach it to Gui. Construct a Gui, set its size and make it visible. What does this program not do?

Responding to events:

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){} } Attach a observer to “listen” for events that might occur on this window. Create a simple button, then add it to the Gui Frame. Attach an observer to listen to events on this button. Listen for these events that can occur on a Window. When the ActionEvent labeled "press me" occurs, print (ring) the bell.

Responding to events, continued:

Responding to events, continued Uses event delegation model of JDK 1.1 When an event occurs, it generates an ActionEvent object ActionListener interface listens for a particular 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 Button: actionPerformed method rings a bell Also a live close window button, which performs System.exit(0) Most Components in the AWT have corresponding Listeners

Adapter Classes:

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 i mplements an interface Does anyone recognize a design pattern here? Default implementation ({ }, empty body) for all methods You then extend adapter class, overriding methods for events you care about, such as windowClosing . Has "is a" relationship with interface WindowAdapter is a WindowListener MouseAdapter is a MouseListener

Sketchpad example:

Sketchpad example See Sketchpad.java (H:\oose\java, java Sketchpad)

Layout managers:

Layout managers Sketchpad uses hard-coded layout, which depends on a 800x600 screen JDK provides a set of generic layout manager classes Arrange Component objects within a Container object in predictable ways 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

Swing overview:

Swing overview Defined in package javax.swing Original GUI components from AWT in java.awt Heavyweight components - rely on local platform's windowing system for look and feel Swing components are lightweight Not weighed down by GUI capabilities of platform More portable than heavyweight components Swing components allow programmer to specify look and feel Can change depending on platform Can be same across all platforms

Swing component inheritance hierarchy:

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

Jcomponent features:

Jcomponent features Pluggable look and feel Can look like different platforms, at run-time Shortcut keys (mnemonics) Direct access to components through keyboard Common event handling If several components perform same actions Tool tips Describe component when mouse rolls over it

Menus:

Menus Menu Bar JMenuBar() add( JMenu ) Menu JMenu( String ) add( JMenuItem ) 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 ); JMenuItem( String ) JMenuItem( String,int )

JLabel:

JLabel Labels Provide text instructions 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 tip when mouse over label myLabel.setText( "Text" ) myLabel.getText()

JLabel:

JLabel Icon Object that implements interface Icon One class is ImageIcon ( .gif and .jpeg images) Assumed same directory as program Display an icon with JLabel ’s setIcon method myLabel.setIcon( myIcon ); myLabel.getIcon //returns current Icon 24 Icon bug = new ImageIcon( "bug1.gif" ); 33 label3.setIcon( bug );

Slide 24:

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. Create a new ImageIcon (assumed to be in same directory as program). Set ImageIcon and alignment of text in JLabel constructor. Set the tool tip text, and attach component to Container c .

JButton:

JButton 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 button Class ActionEvent getActionCommand returns label of button that generated event Icon bug1 = new ImageIcon( "bug1.gif" ); fancyButton = new JButton( "Fancy Button", bug1 ); fancyButton.setRolloverIcon( bug2 );

JCheckBox:

JCheckBox When JCheckBox changes ItemEvent generated Handled by an ItemListener , which must define itemStateChanged Register handlers with with addItemListener Class ItemEvent getStateChange Returns ItemEvent.SELECTED or ItemEvent.DESELECTED private class CheckBoxHandler implements ItemListener { public void itemStateChanged( ItemEvent e )

Slide 27:

1. import 1.1 Declarations 1.2 Initialize JCheckBox es 1.3 Register event handler 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", Font.PLAIN, 14 ) ); 20 c.add( t ); 21 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 JCheckBox es

Slide 28:

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

JRadioButton:

JRadioButton Radio buttons Have two states: selected and deselected Normally appear as a group Only one radio button in group selected at time Selecting one button forces the other buttons off Mutually exclusive options ButtonGroup - maintains logical relationship between radio buttons Class JRadioButton Constructor JRadioButton( "Label", selected ) If selected true , JRadioButton initially selected

Slide 30:

1. import 1.1 Declarations 1.2 Initialization 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() ); 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.

Slide 31:

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

JList:

JList List Displays series of items may select one or more items Class JList Constructor JList( arrayOfNames ) Takes array of Objects ( String s) to display in list setVisibleRowCount( n ) Displays n items at a time Does not provide automatic scrolling

Slide 34:

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 String s, 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 ).

Slide 35:

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.

Slide 36:

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.

Slide 37:

Program Output 59 setTitle( s ); // set the title bar of the window 60 repaint(); 61 } 62 } 63 } Set the Frame’s title bar.

Learn more about Swing compenents:

Learn more about Swing compenents http://java.sun.com/docs/books/tutorial/uiswing/components/componentlist.html

Good and bad programming practices with AWT:

Good and bad programming practices with AWT Separate user interface logic from "business logic" or model AWT 1.1 "listeners" designed for this purpose; inner classes facilitate it further Separation.java example illustrates this approach: class BusinessLogic knows nothing about UI; class Separation keeps track of all UI details and talks to BusinessLogic through its public interface. How is this design loosely coupled? How does it support reuse? How does it support legacy code? Also note use of inner classes for all "listeners" nested within Separation Contrast code of badidea1.java : look at code in actionPerformed: public void actionPerformed(ActionEvent e) { Object source = e.getSource(); if (source == b1) System.out.println("Button 1 pressed"); else if (source == b2) System.out.println("Button 2 pressed"); else System.out.println("Something else"); } badidea2.java improves on things by using adapters, but ... Why is the cascaded if above a bad idea?

JThankYou:

JThankYou

Eclipse Widgets:

Eclipse Widgets Standard Widget Toolkit (SWT) GUI toolkit released in November 2001 Initially designed for the Eclipse IDE “Best of both worlds” approach – use native functionality when available, and Java implementation when unavailable Takes on the appearance and behavior of the native platform The code YOU write will be portable for all the platforms that have SWT implementations http://www.eclipse.org/swt/ - SWT home page