GUI Properties in Java

1
GUI Properties in Java
2
Java Basic GUI Components

• Swing component overview
• Event handling
• Inner classes and anonymous inner classes
• Examples and various components
• Layouts
• Panels

3
Swing Components

• Lightweight vs. heavyweight components
• Lightweight platform independent
• Heavyweight tied to platform windowing system
• Peer object object responsible for interactions
  between heavyweight object and local system
• Swing components are lightweight

4
The JFrame Class
5
Example

• import java.awt.
• import java.awt.event.
• import javax.swing.
• public class FrameDemo
• public static void main(String s)
• JFrame frame new JFrame("FrameDemo")
• frame.addWindowListener(new WindowAdapter()
• public void windowClosing(WindowEvent e)
• System.exit(0)
• )
• JLabel emptyLabel new JLabel("")
• emptyLabel.setPreferredSize(new Dimension(175,
  100))
• frame.getContentPane().add(emptyLabel,
  BorderLayout.CENTER)
• frame.pack()
• frame.setVisible(true) // show() is
  deprecated

6
The Event Handing Model

• GUI components are event-driven
• Programmer must
• register events
• implement event handlers
• Event registration add listeners
• Event implementation define listener methods

7
Example Registering Events

• public class TextFieldTest extends JFrame
• private JTextField text1, text2, text3
• private JPasswordField password
• public TextFieldTest()
• super( "Testing JTextField and JPasswordField"
  )
• Container c getContentPane()
• c.setLayout( new FlowLayout() )
• // construct textfield with default sizing
• text1 new JTextField( 10 )
• c.add( text1 )
• // construct textfield with default text
• text2 new JTextField( "Enter text here" )
• c.add( text2 )

8
Example (cont.)

• // construct textfield with default text and
• // 20 visible elements and no event handler
• text3 new JTextField( "Uneditable text
  field", 20 )
• text3.setEditable( false )
• c.add( text3 )
• // construct textfield with default text
• password new JPasswordField( "Hidden text" )
• c.add( password )
• TextFieldHandler handler new
  TextFieldHandler()
• text1.addActionListener( handler )
• text2.addActionListener( handler )
• text3.addActionListener( handler )
• password.addActionListener( handler )
• setSize( 325, 100 )
• show()

9
Listeners for Event Types

• ActionListener
• MouseListener
• MouseMotionListener
• KeyListener
• ButtonChangeListener
• AncestorListener
• PropertyChangeListener
• ...

10
ActionListener Interface
11
actionPerformed method
12
Example Handling Events

• // inner class for event handling
• private class TextFieldHandler implements
  ActionListener
• public void actionPerformed( ActionEvent e )
• String s ""
• if ( e.getSource() text1 )
• s "text1 " e.getActionCommand()
• else if ( e.getSource() text2 )
• s "text2 " e.getActionCommand()
• else if ( e.getSource() text3 )
• s "text3 " e.getActionCommand()
• else if ( e.getSource() password )
• JPasswordField pwd (JPasswordField)
  e.getSource()
• s "password " new String(
  pwd.getPassword() )
• JOptionPane.showMessageDialog( null, s )

13
Event Handling and Inner Classes

• Event handler classes are usually private
• Often event handlers are anonymous inner classes
  defined purely to implement the handing method

14
Driver for Example

• public static void main( String args )
• TextFieldTest app new TextFieldTest()
• app.addWindowListener(new WindowAdapter()
• public void windowClosing(WindowEvent e)
• System.exit( 0 )
• )

15
GUI Components

• JTextField and JPasswordField
• JButton
• JCheckBox and JRadioButton
• JComboBox
• JList and Multiple Selection Lists

16
SwingSet Demo
17
Mouse Interaction

• // Fig. 12.17 MouseTracker.java
• // Demonstrating mouse events.
• import java.awt.
• import java.awt.event.
• import javax.swing.
• public class MouseTracker extends JFrame
• implements MouseListener, MouseMotionListener
• private JLabel statusBar
• public MouseTracker()
• super( "Demonstrating Mouse Events" )
• statusBar new JLabel()
• getContentPane().add( statusBar,
  BorderLayout.SOUTH )
• // application listens to its own mouse events
• addMouseListener( this )
• addMouseMotionListener( this )
• setSize( 275, 100 )
• show()

18
Mouse Interaction (cont.)

• // MouseListener event handlers
• public void mouseClicked( MouseEvent e )
• statusBar.setText( "Clicked at " e.getX()
  ", " e.getY() "" )
• public void mousePressed( MouseEvent e )
• statusBar.setText( "Pressed at " e.getX()
  ", " e.getY() "" )
• public void mouseReleased( MouseEvent e )
• statusBar.setText( "Released at " e.getX()
  ", " e.getY() "" )
• public void mouseEntered( MouseEvent e )
• statusBar.setText( "Mouse in window" )
• public void mouseExited( MouseEvent e )

19
Mouse Interaction (cont.)

• // MouseMotionListener event handlers
• public void mouseDragged( MouseEvent e )
• statusBar.setText( "Dragged at " e.getX()
  ", " e.getY() "" )
• public void mouseMoved( MouseEvent e )
• statusBar.setText( "Moved at " e.getX() ",
  " e.getY() "" )
• public static void main( String args )
• MouseTracker app new MouseTracker()
• app.addWindowListener(new WindowAdapter()
• public void windowClosing( WindowEvent e )
• System.exit( 0 )
• )

20
Adapter Classes

• Interfaces with many methods to implement can be
  cumbersome
• The adapter class provides a default
  implementation of all interface methods
• Application can over-ride interface methods that
  are of interest

21
Java-Based GUI Components

• Layout managers
• Panels
• Customized panels
• Menus
• More layout

22
Simple Layout Managers

• Automatic control over component placement
  according to layout scheme
• API for particular layout scheme provides tunable
  options

23
BorderLayout

• Default layout manager for the content pane
• Implements the LayoutManager2 interface
• Lays out components based on a compass scheme
• Rules for expansion/filling when components
  are left out of the compass positions

24
FlowLayout

• Adds components to the panel in the first open
  spot as they are added
• Nice for quick (sometimes ugly) layout of button
  banks or text boxes

25
GridLayout

• Arranges components into rows and columns
• Must specify rows and columns
• Nice for an organized look for lists of elements
  (like a spreadsheet)

26
Using Panels

• Panels can have their own layout
• Multiple panels can be added to the container

27
Menus and JFrame

• JMenuBar, JMenuItem, JMenu
• Objects of classes that provide setJMenuBar()
  are able to support menus JFrame, JApplet
• Customization/added functionality
• JCheckBoxMenuItem,
• JRadioButtonMenuItem

28
Menu Example

• // Fig. 13.7 MenuTest.java
• // Demonstrating menus
• import javax.swing.
• import java.awt.event.
• import java.awt.
• public class MenuTest extends JFrame
• private Color colorValues Color.black,
  Color.blue, Color.red, Color.green
• private JRadioButtonMenuItem colorItems,
  fonts
• private JCheckBoxMenuItem styleItems
• private JLabel display
• private ButtonGroup fontGroup, colorGroup
• private int style
• public MenuTest()
• super( "Using JMenus" )
• JMenuBar bar new JMenuBar() // create
  menubar
• setJMenuBar( bar ) // set the menubar for the
  JFrame

29
Menu Example (cont.)

• // create File menu and Exit menu item
• JMenu fileMenu new JMenu( "File" )
• fileMenu.setMnemonic( 'F' )
• JMenuItem aboutItem new JMenuItem( "About..."
  )
• aboutItem.setMnemonic( 'A' )
• aboutItem.addActionListener(new
  ActionListener()
• public void actionPerformed( ActionEvent e )
• JOptionPane.showMessageDialog( MenuTest.th
  is,
• "This is an example\n of using
  menus",
• "About", JOptionPane.PLAIN_MESSAGE)
• )
• fileMenu.add( aboutItem )

30
Menu Example (cont.)

• JMenuItem exitItem new JMenuItem( "Exit" )
• exitItem.setMnemonic( 'x' )
• exitItem.addActionListener(
• new ActionListener()
• public void actionPerformed( ActionEvent e )
• System.exit( 0 )
• )
• fileMenu.add( exitItem )
• bar.add( fileMenu ) // add File menu
• // create the Format menu, its submenus and
  menu items
• JMenu formatMenu new JMenu( "Format" )
• formatMenu.setMnemonic( 'r' )
• // create Color submenu
• String colors "Black", "Blue", "Red",
  "Green"
• JMenu colorMenu new JMenu( "Color" )
• colorMenu.setMnemonic( 'C' )
• colorItems new JRadioButtonMenuItem
  colors.length

31
Menu Example Run
32
Snazzy and Fun

• Pop-up menus
• Internal frames
• Look and feel options