Advanced GUI

1
Advanced GUI

• Robert Salkin
• CSI 445 Advanced Java
• Summer 2006, 6W3

2
What is a GUI?

• GUI Graphical User Interface
• A GUI allows the user to interact with the
  program in a more intuitive manner.
• A GUI is usually preferred over a command-line
  interface.

3
Lightweight vs. Heavyweight

• A heavyweight component is one that is associated
  with its own native screen resource (commonly
  known as a peer).
• A lightweight component is one that "borrows" the
  screen resource of an ancestor (which means it
  has no native resource of its own -- so it's
  "lighter").
• Lightweight components sit on top of heavyweight
  components.
• Always, ALWAYS, use lightweight (Swing or J)
  components when you can.
• All AWT components are heavyweight and all Swing
  components are lightweight, except for the
  top-level ones
• JWindow
• JFrame
• JDialog
• JApplet
• The differences boil down to the following
• A lightweight component can have transparent
  pixels a heavyweight is always opaque.
• A lightweight component can appear to be
  non-rectangular because of its ability to set
  transparent areas a heavyweight can only be
  rectangular.
• Mouse events on a lightweight component fall
  through to its parent mouse events on a
  heavyweight component do not fall through to its
  parent.
• When a lightweight component overlaps a
  heavyweight component, the heavyweight component
  is always on top, regardless of the relative
  z-order  of the two components.
• From http//java.sun.com/products/jfc/tsc/article
  s/mixing/

4
GUI Components Hierarchy

• Object
• Component
• Container
• JContainer
• GUI components inherit from Component.
• Container is a GUI component that can hold other
  components.
• Notice that Container is a Component so
  Containers can be added to other Containers.
• JComponent is the lightweight version of
  Container and is, therefore, the superclass of
  all lightweight Swing components.

5
Helpful Classes

• JOptionPane
• Static methods to create popup windows.
• You can use
• showInputDialog()
• showMessageDialog()
• showConfirmDialog()
• showOptionDialog()
• More universal, less easy.
• JFrame
• Used to create a program window.
• JPanel
• Container for Components.
• BorderFactory
• Static methods to create borders for JPanels.

6
Helpful Classes (contd)

• JLabel
• Text that cannot be modified by the user.
• JTextField
• Allows for data entry by the user.
• JButton
• Creates a button (and allows for click events).

7
Helpful Classes (contd)

• JCheckBox
• Gives the user an option to select (or not).
• JComboBox
• Makes a drop-down list.
• JList
• A list of options the user can select none, one,
  or more of.

8
Layout Managers

• FlowLayout
• Adds in order, from upper left to bottom right.
• BorderLayout
• Adds to one of 5 areas of the screen.
• Default for JFrame.
• GridLayout
• Rows and column layout.
• My favorite fast and easy.
• GridBagLayout
• Like GridLayout, but much more complex.
• Uses Constraints to position Components.
• BoxLayout
• Allows for components to be arranged
  left-to-right or top-to-bottom.

9
Painting

• To draw on the screen, implement your own
• public void paintComponent(Graphics g)
• To redraw the screen (by calling paintComponent
  indirectly), call
• repaint()
• Using the Graphics object, you draw many objects
  and set the background color.

10
More Advanced GUI Classes

• JSlider
• Allows the user to select from different values
  using a slider bar.
• JMenuBar
• Allows for menus, using
• JMenuItem
• JCheckBoxMenuItem
• JRadioButtonMenuItem
• JPopupMenu
• Allows for context-sensitive menus.

11
More Advanced GUI Classes (contd)

• JDesktopPane
• Allows for JInternalFrame objects to act as
  windows within the parent window.
• JTabbedPane
• Allows for tabbed panes.

12
Look-and-Feel

• A Pluggable Look-and-Feel allows the programmer
  to change the appearance, or look-and-feel, of
  the program.
• Using UIManager and SwingUtilities, the
  programmer can switch between available modes.

13
Model-View-Controller (MVC)

• For flexibility and portability, implement a GUI
  using MVC.
• Model
• Holds data and some algorithms.
• View
• The display of the underlying model, probably in
  some type of GUI.
• Controller
• Handles events, possibly modifying the Model and
  View.
• The View and Controller are usually linked, since
  the Controller must be customized for each
  different View.
• The Model is not dependent on the View or
  Controller.
• This will not be covered in detail, but it was
  important to be mentioned.