CS1020

1
The javax.swing package contains several classes
used for creating Menus

• JMenuBar, JMenu, JMenuItem (and variants)
• JRadioButtonMenuItem
• JCheckboxMenuItem
• Only the JMenuItem objects (and variants)
  generate events.

2
JMenuItems generate Action Events
3
JMenuBar

• JMenuBar is a bar where the menus are placed.
• There is only one menu bar per frame.

4
JMenu

• JMenu (such as File or Edit) is a group of menu
  choices.
• A JMenuBar object may include many JMenu objects.

5
JMenuItem

• JMenuItem (such as Copy, Cut, or Paste) is an
  individual menu choice in a JMenu object.
• Action command defaults to text of menu item
• Override with call to setActionCommand()
• Useful when providing UI in multiple languages

6
Demo

• Menus

7
Sequence for Creating Menus

• Create a JMenuBar object and add it to a frame
  via setJMenuBar()
• Create a JMenu object.
• Create JMenuItem objects and add them to the
  JMenu object.
• Add the JMenu object to the JMenuBar object.

8
Radio buttons and Check boxes

• Along with JButton, Radio buttons and Check boxes
  are all specific kinds of buttons they all
  derive from the AbstractButton class
• This is called inheritance coming soon
• This implies similar behavior for these classes

9
Check boxes

• Implemented by JCheckBox
• A GUI usually permits more than one Check box to
  be selected at one time

10
Radio Buttons

• Implemented by JRadioButton
• A GUI usually prevents more than one Radio button
  to be selected at once
• Typically used along with a ButtonGroup object
• ButtonGroup takes care of deselecting the
  previous Radio button when a new one is selected

11
Mouse Events

• Mouse events arise from such user interactions as
  
• moving the mouse
• dragging the mouse (moving the mouse while the
  mouse button is being pressed)
• clicking the mouse buttons.
• Who listens for Mouse Events?
• JFrame
• ContentPane
• or whoever is interested in getting events

12
Handling Mouse Events

• A MouseListener handles most mouse events
• mouseEntered cursor crossed into the boundary
• mouseExited cursor crossed out of the boundary
• mousePressed button down (specifics in
  MouseEvent)
• mouseReleased button up
• mouseClicked button down/up in quick succession
• A MouseMotionListener handles mouse movement
• mouseDragged mouse moved while button down
• mouseMoved mouse moved while button up
• Point location info in MouseEvent
• Location is relative to the listening components
  origin