Download An Introduction to Control Structures

Common Elements of
Graphical User Interfaces
Chapter 6
Java Programming: Advanced Topics
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Objectives
• Learn the characteristics of a graphical user
interface
• Explore the contents of the Java Foundation
Classes
• Discover how the JFC supports creating GUIs
for the Java platform
• Design GUIs with layouts that dynamically adjust
to screen resolution and window size
• Include predefined components such as text
fields, buttons, and multimedia elements in your
GUI
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Objectives (Cont.)
• See how the JFC provides a framework for
interacting with the user in event-driven
programs
• Write code using component, container, and
layout manager classes of the AWT and Swing
• State the name of the event class for any
specified listener interface in the java.awt.event
package
• Write code to implement the paintComponent
method of a javax.swing.Jcomponent
component
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Main Features and Terminology
of a GUI
• Components are predefined standard elements
(such as buttons, text fields, frame windows, and
dialog boxes)
• The layout managers control the way
components are arranged within a container
• Graphics: drawing in the graphics context for a
component
• Graphics context: is the area on the display
screen where a component is positioned
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Main Features and Terminology
of a GUI (Cont.)
• Painting: the process of displaying components
or refreshing the display of components on the
screen
• Events can be triggered by the operating system
or by user actions
• The adapter is a class that implements all the
methods of the interface by providing empty
methods for all of them
• Each listener interface that has more than one
method also has a corresponding adapter class
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Introducing the Java Foundation
Classes
• The goal of the JFC is to simplify the
development of 100% Pure Java programs for
network or standalone environments
• The classes enable you to:
– Design GUIs that reflect the operating system that is
host to the JVM
– Create your own platform-independent interface
– Use a look and feel defined for the Java platform and
common across all implementations of the JVM
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Introducing the Java Foundation
Classes
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Introducing the Java Foundation
Classes
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Abstract Windowing Toolkit API
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Abstract Windowing Toolkit API
(Cont.)
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Abstract Windowing Toolkit API
(Cont.)
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Event Model
• Define any class to be an event handler by
implementing a listener interface
• Call a method of a component class to register
the listener with the component
• When an event that relates to the component
occurs, only the registered listeners are notified
and passed a copy of the event
• The event model is consistent with the
JavaBeans interface
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Swing API
• The Swing API consists of more than 250
classes and 75 interfaces grouped into the
following categories:
– JComponent: extends the AWT class
Container and a set of components that are
subclasses of JComponent
– Nonvisible support classes that provide
important services
– A set of related interfaces that are
implemented by Swing component and
support classes
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Swing Components
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Swing Components (Cont.)
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Swing Components (Cont.)
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Swing Components (Cont.)
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Separable Model Architecture
• Swing components separate the manipulation of
data associated with a component from the
rendering or graphical-representation
component and its contents
• The Swing API uses a separable model
architecture
• Swing models use two different styles of
notification:
– Lightweight
– Stateful
• The Swing API defines a set of model interfaces
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Swing Model Interfaces
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Swing Model Interfaces (Cont.)
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An Example of JFC Program
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Layout Managers
• Layout managers automate the positioning of
components within containers
• Standard layout managers:
–
–
–
–
–
–
BorderLayout
FlowLayout
GridLayout
GridBagLayout
BoxLayout
CardLayout
• The javax.swing.JTabbedPane and
javax.swing.JSplitPane containers in the Swing
API have built-in layout characteristics
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Layout Managers and Related
Interfaces
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Border Layouts
• The BorderLayout class implements the
LayoutManager2 interface to support a container
that holds up to five components:
–
–
–
–
–
North
South
West
East
Center
• By default, the JWindow, JFrame, and JDialog
containers have border layouts
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The BorderLayout Strategy
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Flow Layouts
• The class FlowLayout implements the
LayoutManager interface
• Components are arranged in a row across
the area of the container
• Components in a flow layout retain their
preferred size
• By default, JPanel objects have flow
layouts
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A FlowLayout Example
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Grid Layouts
• The class GridLayout implements the
LayoutManager2 interface
• GridLayout manager divides the area of the
container into a grid of equally sized rows and
columns
• Components are automatically put into the next
cell, in a left to right order, filling rows from top to
bottom
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A GridLayout Example
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Grid-Bag Layouts
• The class GridBagLayout implements the
LayoutManager2 interface to support grid-bag
layouts
• A grid-bag layout is based on a rectangular grid,
and it uses a helper class, GridBagConstraints,
to specify how each component should be
located within the grid
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A GridBagLayout Example
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Events
• Events: objects that encapsulate changes in
state that are initiated by the user or the
operating system
• The AWT API includes the package
java.awt.event of the classes that encapsulate
the events that relate to the GUI components in
your application or applet
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AWT Event Classes
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AWT Event Classes(Cont.)
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Swing Event Classes
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Selected Methods of the Event
Classes
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Selected Methods of the Event
Classes (Cont.)
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Events that Start Long
Operations
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Painting
• Painting: the act of drawing onto the graphics
context of a component
• All objects that are instances of subclasses of
java.awt.Component handle their own painting
• The key methods:
–
–
–
–
void paintComponent (Graphics context)
void paint (Graphics context)
void repaint (long time)
void update (Graphics context)
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Basic Support for Graphics
• The AWT API provides basic graphics support
through the class Graphics
• The drawing methods of the class Graphics are
instance methods of the Graphics class, and
each instance of Graphics is the graphics
context for a component
• The Graphics class provides a number of
methods for drawing onto a component
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Java 2D API
• The basic support for drawing was lacking for
high-quality graphics
• The goal was to create an API that addressed
the needs of graphics professionals
• The Java 2D API was created and included as
part of the JFC
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Notable Java 2D Features
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Summary
• The JFC consists of five major APIs, including
the classes and interfaces in the AWT and
Swing APIs that you use to program a GUI for
an application or applet
• Layout managers are used to arrange the
components in a way that adjusts for screen
resolutions and window resizings
• Standard layout managers include
BorderLayout, FlowLayout, GridLayout,
GridBagLayout, Box, and CardLayout
• Each component class supports a number of
events that are appropriate to its type of
component
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Summary (Cont.)
• The AWT contains a hierarchy of event classes
for different kinds of user-initiated events, such
as ComponentEvent, MouseEvent, KeyEvent,
ItemEvent, TextEvent, and ActionEvent
• Each listener interface that has more than one
method also has a corresponding adapter class
• Painting is the act of drawing onto the graphics
context of a component, and drawing methods of
the Graphics class are paintComponent, paint,
and update methods of a component
• The goal of the Java 2D API addresses the
needs of graphics professionals
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