Download Chapter 10 Getting Started with Graphics Programming

Chapter 13 GUI Basics
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1
Motivations
The design of the API for Java GUI programming
is an excellent example of how the object-oriented
principle is applied. In the chapters that follow, you
will learn the framework of Java GUI API and use
the GUI components to develop user-friendly
interfaces for applications and applets.
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Creating GUI Objects
// Create a button with text OK
JButton jbtOK = new JButton("OK");
// Create a label with text "Enter your name: "
JLabel jlblName = new JLabel("Enter your name: ");
Label
Text
field
Check
Box
Radio
Button
Button
// Create a text field with text "Type Name Here"
JTextField jtfName = new JTextField("Type Name Here");
Combo
Box
// Create a check box with text bold
JCheckBox jchkBold = new JCheckBox("Bold");
// Create a radio button with text red
JRadioButton jrbRed = new JRadioButton("Red");
// Create a combo box with choices red, green, and blue
JComboBox jcboColor = new JComboBox(new String[]{"Red",
"Green", "Blue"});
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Swing vs. AWT
So why do the GUI component classes have a prefix J? Instead of JButton, why
not name it simply Button? In fact, there is a class already named Button in the
java.awt package.
When Java was introduced, the GUI classes were bundled in a library known as
the Abstract Windows Toolkit (AWT). For every platform on which Java runs, the
AWT components are automatically mapped to the platform-specific components
through their respective agents, known as peers. AWT is fine for developing
simple graphical user interfaces, but not for developing comprehensive GUI
projects. Besides, AWT is prone to platform-specific bugs because its peer-based
approach relies heavily on the underlying platform. With the release of Java 2, the
AWT user-interface components were replaced by a more robust, versatile, and
flexible library known as Swing components. Swing components are painted
directly on canvases using Java code, except for components that are subclasses of
java.awt.Window or java.awt.Panel, which must be drawn using native GUI on a
specific platform. Swing components are less dependent on the target platform and
use less of the native GUI resource. For this reason, Swing components that don’t
rely on native GUI are referred to as lightweight components, and AWT
components are referred to as heavyweight components.
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Container Classes
Dimension
Classes in the java.awt
package
LayoutManager
Font
Heavyweight
1
FontMetrics
Object
Color
Panel
Applet
JApplet
Window
Frame
JFrame
Dialog
JDialog
Graphics
Component
Container
*
Container classes can
contain other GUI
components.
JComponent
JPanel
Swing Components
in the javax.swing package
Lightweight
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GUI Helper Classes
Dimension
Font
Classes in the java.awt
package
LayoutManager
Heavyweight
1
FontMetrics
Object
Color
Panel
Applet
JApplet
Window
Frame
JFrame
Dialog
JDialog
Graphics
Component
Container
*
The helper classes are not subclasses
of Component. They are used to
describe the properties of GUI
components such as graphics context,
colors, fonts, and dimension.
JComponent
JPanel
Swing Components
in the javax.swing package
Lightweight
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Swing GUI Components
JCheckBoxMenuItem
AbstractButton
JComponent
JMenuItem
JMenu
JButton
JRadioButtonMenuItem
JToggleButton
JCheckBox
JRadioButton
JEditorPane
JTextComponent
JTextField
JPasswordField
JTextArea
JLabel
JTabbedPane
JToolBar
JTree
JComboBox
JList
JSplitPane
JMenuBar
JTable
JPanel
JLayeredPane
JPopupMenu
JTableHeader
JOptionPane
JSeparator
JFileChooser
JInternalFrame
JScrollBar
JSlider
JScrollPane
JRootPane
JColorChooser
JProgressBar
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JToolTip
JSpinner
7
Components Covered in the Comprehensive Version
JCheckBoxMenuItem
AbstractButton
JComponent
JMenuItem
JMenu
JButton
JRadioButtonMenuItem
JToggleButton
JCheckBox
JRadioButton
JEditorPane
JTextComponent
JTextField
JPasswordField
JTextArea
JLabel
JTabbedPane
JToolBar
JTree
JComboBox
JList
JSplitPane
JMenuBar
JTable
JPanel
JLayeredPane
JPopupMenu
JTableHeader
JOptionPane
JSeparator
JFileChooser
JInternalFrame
JScrollBar
JSlider
JScrollPane
JRootPane
JColorChooser
JProgressBar
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JToolTip
JSpinner
8
AWT (Optional)
AWTEvent
Font
FontMetrics
Object
Color
Graphics
Component
Container
Panel
Applet
Button
Window
Frame
Label
TextField
Dialog
FileDialog
TextComponent
List
TextArea
Choice
CheckBox
LayoutManager
CheckBoxGroup
Canvas
MenuComponent
Scrollbar
MenuItem
Menu
MenuBar
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Frames
 Frame
is a window that is not contained inside
another window. Frame is the basis to contain
other user interface components in Java GUI
applications.
 The
JFrame class can be used to create
windows.
 For
Swing GUI programs, use JFrame class to
create widows.
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Creating Frames
import javax.swing.*;
public class MyFrame {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(400, 300);
frame.setVisible(true);
frame.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE);
}
}
MyFrame
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11
Adding Components into a Frame
Title bar
// Add a button into the frame
frame.getContentPane().add(
new JButton("OK"));
Content pane
MyFrameWithComponents
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Content Pane Delegation in JDK 1.5
// Add a button into the frame
frame.getContentPane().add(
new JButton("OK"));
Title bar
Content pane
// Add a button into the frame
frame.add(
new JButton("OK"));
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JFrame Class
javax.swing.JFrame
+JFrame()
Creates a default frame with no title.
+JFrame(title: String)
Creates a frame with the specified title.
+setSize(width: int, height: int): void
Specifies the size of the frame.
+setLocation(x: int, y: int): void
Specifies the upper-left corner location of the frame.
+setVisible(visible: boolean): void
Sets true to display the frame.
+setDefaultCloseOperation(mode: int): void
Specifies the operation when the frame is closed.
+setLocationRelativeTo(c: Component):
void
Sets the location of the frame relative to the specified component.
If the component is null, the frame is centered on the screen.
+pack(): void
Automatically sets the frame size to hold the components in the
frame.
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Layout Managers

Java’s layout managers provide a level of abstraction to
automatically map your user interface on all window
systems.

The UI components are placed in containers. Each
container has a layout manager to arrange the UI
components within the container.

Layout managers are set in containers using the
setLayout(LayoutManager) method in a container.
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FlowLayout Example
Write a program that
adds three labels and
text fields into the
content pane of a
frame with a
FlowLayout manager.
ShowFlowLayout
Run
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The FlowLayout Class
java.awt.FlowLayout
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
-alignment: int
The alignment of this layout manager (default: CENTER).
-hgap: int
The horizontal gap of this layout manager (default: 5 pixels).
-vgap: int
The vertical gap of this layout manager (default: 5 pixels).
+FlowLayout()
Creates a default FlowLayout manager.
+FlowLayout(alignment: int)
Creates a FlowLayout manager with a specified alignment.
+FlowLayout(alignment: int, hgap:
int, vgap: int)
Creates a FlowLayout manager with a specified alignment,
horizontal gap, and vertical gap.
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GridLayout Example
Rewrite the program in
the preceding example
using a GridLayout
manager instead of a
FlowLayout manager to
display the labels and
text fields.
ShowGridLayout
Run
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The GridLayout Class
java.awt.GridLayout
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
-rows: int
The number of rows in this layout manager (default: 1).
-columns: int
The number of columns in this layout manager (default: 1).
-hgap: int
The horizontal gap of this layout manager (default: 0).
-vgap: int
The vertical gap of this layout manager (default: 0).
+GridLayout()
Creates a default GridLayout manager.
+GridLayout(rows: int, columns: int) Creates a GridLayout with a specified number of rows and columns.
+GridLayout(rows: int, columns: int, Creates a GridLayout manager with a specified number of rows and
hgap: int, vgap: int)
columns, horizontal gap, and vertical gap.
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The BorderLayout Manager
The BorderLayout
manager divides the
container into five areas:
East, South, West, North,
and Center. Components are
added to a BorderLayout
by using the add method.
add(Component,
constraint), where
constraint is
BorderLayout.EAST,
BorderLayout.SOUTH,
BorderLayout.WEST,
BorderLayout.NORTH, or
BorderLayout.CENTER.
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BorderLayout Example
ShowBorderLayout
Run
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The BorderLayout Class
java.awt.BorderLayout
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
-hgap: int
The horizontal gap of this layout manager (default: 0).
-vgap: int
The vertical gap of this layout manager (default: 0).
+BorderLayout()
Creates a default BorderLayout manager.
+BorderLayout(hgap: int, vgap: int) Creates a BorderLayout manager with a specified number of
horizontal gap, and vertical gap.
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The Color Class
You can set colors for GUI components by using the
java.awt.Color class. Colors are made of red, green, and
blue components, each of which is represented by a byte
value that describes its intensity, ranging from 0 (darkest
shade) to 255 (lightest shade). This is known as the RGB
model.
Color c = new Color(r, g, b);
r, g, and b specify a color by its red, green, and blue
components.
Example:
Color c = new Color(228, 100, 255);
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Standard Colors
Thirteen standard colors (black, blue, cyan, darkGray,
gray, green, lightGray, magenta, orange, pink, red, white,
yellow) are defined as constants in java.awt.Color.
The standard color names are constants, but they are
named as variables with lowercase for the first word and
uppercase for the first letters of subsequent words. Thus
the color names violate the Java naming convention.
Since JDK 1.4, you can also use the new constants:
BLACK, BLUE, CYAN, DARK_GRAY, GRAY,
GREEN, LIGHT_GRAY, MAGENTA, ORANGE, PINK,
RED, WHITE, and YELLOW.
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Setting Colors
You can use the following methods to set the
component’s background and foreground colors:
setBackground(Color c)
setForeground(Color c)
Example:
jbt.setBackground(Color.yellow);
jbt.setForeground(Color.red);
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The Font Class
Font Names
Standard font names
that are supported in
all platforms are:
SansSerif, Serif,
Monospaced, Dialog,
or DialogInput.
Font Style
Font.PLAIN (0),
Font.BOLD (1),
Font.ITALIC (2), and
Font.BOLD +
Font.ITALIC (3)
Font myFont = new Font(name, style, size);
Example:
Font myFont = new Font("SansSerif ", Font.BOLD, 16);
Font myFont = new Font("Serif", Font.BOLD+Font.ITALIC, 12);
JButton jbtOK = new JButton("OK“);
jbtOK.setFont(myFont);
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Finding All Available Font
Names
GraphicsEnvironment e =
GraphicsEnvironment.getLocalGraphicsEnvironment();
String[] fontnames =
e.getAvailableFontFamilyNames();
for (int i = 0; i < fontnames.length; i++)
System.out.println(fontnames[i]);
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Using Panels as Sub-Containers

Panels act as sub-containers for grouping user interface
components.

It is recommended that you place the user interface
components in panels and place the panels in a frame.
You can also place panels in a panel.

To add a component to JFrame, you actually add it to
the content pane of JFrame. To add a component to a
panel, you add it directly to the panel using the add
method.
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Creating a JPanel
You can use new JPanel() to create a panel with a default
FlowLayout manager or new JPanel(LayoutManager) to
create a panel with the specified layout manager. Use the
add(Component) method to add a component to the
panel. For example,
JPanel p = new JPanel();
p.add(new JButton("OK"));
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Testing Panels Example
This example uses panels to organize components.
The program creates a user interface for a
Microwave oven.
frame
A textfield
p2
A button
12
buttons
p1
TestPanels
Run
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Common Features of Swing Components
java.awt.Component
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
-font: java.awt.Font
The font of this component.
-background: java.awt.Color
The background color of this component.
-foreground: java.awt.Color
The foreground color of this component.
-preferredSize: Dimension
The preferred size of this component.
-visible: boolean
Indicates whether this component is visible.
+getWidth(): int
Returns the width of this component.
+getHeight(): int
Returns the height of this component.
+getX(): int
getX() and getY() return the coordinate of the component’s
upper-left corner within its parent component.
+getY(): int
java.awt.Container
+add(comp: Component): Component
Adds a component to the container.
+add(comp: Component, index: int): Component Adds a component to the container with the specified index.
Removes the component from the container.
+remove(comp: Component): void
+getLayout(): LayoutManager
Returns the layout manager for this container.
+setLayout(l: LayoutManager): void
Sets the layout manager for this container.
+paintComponents(g: Graphics): void
Paints each of the components in this container.
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
javax.swing.JComponent
-toolTipText: String
The tool tip text for this component. Tool tip text is displayed when
the mouse points on the component without clicking.
-border: javax.swing.border.Border
The border for this component.
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Borders
You can set a border on any object of the
JComponent class. Swing has several types of
borders. To create a titled border, use
new TitledBorder(String title).
To create a line border, use
new LineBorder(Color color, int width),
where width specifies the thickness of the line.
For example, the following code displays a titled
border on a panel:
JPanel panel = new JPanel();
panel.setBorder(new TitleBorder(“My Panel”));
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Test Swing Common Features
Component Properties
JComponent Properties
font
 background
 foreground
 preferredSize
 minimumSize
 maximumSize
 toolTipText

 border
TestSwingCommonFeatures
Run
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Image Icons
Java uses the javax.swing.ImageIcon class to represent
an icon. An icon is a fixed-size picture; typically it is
small and used to decorate components. Images are
normally stored in image files. You can use new
ImageIcon(filename) to construct an image icon. For
example, the following statement creates an icon from an
image file us.gif in the image directory under the current
class path:
ImageIcon icon = new ImageIcon("image/us.gif");
TestImageIcon
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Chapter 15 Event-Driven
Programming
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Procedural vs. Event-Driven
Programming
 Procedural
programming is executed in
procedural order.
 In
event-driven programming, code is executed
upon activation of events.
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Revisit Listing 11.7
Taste of Event-Driven Programming
 The
example displays a button in the frame. A
message is displayed on the console when a
button is clicked.
HandleEvent
Run
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Events
 An
event can be defined as a type of signal
to the program that something has
happened.
 The
event is generated by external user
actions such as mouse movements, mouse
clicks, and keystrokes, or by the operating
system, such as a timer.
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Event Classes
EventObject
AWTEvent
ActionEvent
ContainerEvent
AdjustmentEvent
FocusEvent
ComponentEvent
InputEvent
ItemEvent
PaintEvent
TextEvent
WindowEvent
MouseEvent
KeyEvent
ListSelectionEvent
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Event Information
An event object contains whatever properties are
pertinent to the event. You can identify the source
object of the event using the getSource() instance
method in the EventObject class. The subclasses of
EventObject deal with special types of events,
such as button actions, window events, component
events, mouse movements, and keystrokes. Table
15.1 lists external user actions, source objects, and
event types generated.
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Selected User Actions
User Action
Source
Object
Event Type
Generated
Click a button
JButton
ActionEvent
Click a check box
JCheckBox
ItemEvent, ActionEvent
Click a radio button
JRadioButton
ItemEvent, ActionEvent
Press return on a text field
JTextField
ActionEvent
Select a new item
JComboBox
ItemEvent, ActionEvent
Window opened, closed, etc.
Window
WindowEvent
Mouse pressed, released, etc.
Component
MouseEvent
Key released, pressed, etc.
Component
KeyEvent
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The Delegation Model
Trigger an event
source: SourceClass
User
Action
XListener
+addXListener(listener: XListener)
(a) A generic source component
with a generic listener
+handler(event: XEvent)
Register by invoking
source.addXListener(listener);
listener: ListenerClass
source: JButton
ActionListener
+addActionListener(listener: ActionListener)
+actionPerformed(event: ActionEvent)
(b) A JButton source component
with an ActionListener
Register by invoking
source.addActionListener(listener);
listener: CustomListenerClass
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Internal Function of a Source Component
source: SourceClass
source: JButton
+addXListener(XListener listener)
An event is
triggered
event: XEvent
Invoke
listener1.handler(event)
listener2.handler(event)
…
listenern.handler(event)
+addActionListener(ActionListener listener)
Keep it a list
An event is
triggered
listener1
listener2
…
listenern
event:
ActionEvent
(a) Internal function of a generic source object
Keep it a list
Invoke
listener1.actionPerformed(event)
listener2.actionPerformed(event)
…
listenern.actionPerformed(event)
listener1
listener2
…
listenern
(b) Internal function of a JButton object
+handler(
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43
The Delegation Model: Example
JButton jbt = new JButton("OK");
ActionListener listener = new OKListener();
jbt.addActionListener(listener);
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Selected Event Handlers
Event Class
Listener Interface
Listener Methods (Handlers)
ActionEvent
ItemEvent
WindowEvent
ActionListener
ItemListener
WindowListener
ContainerEvent
ContainerListener
MouseEvent
MouseListener
KeyEvent
KeyListener
actionPerformed(ActionEvent)
itemStateChanged(ItemEvent)
windowClosing(WindowEvent)
windowOpened(WindowEvent)
windowIconified(WindowEvent)
windowDeiconified(WindowEvent)
windowClosed(WindowEvent)
windowActivated(WindowEvent)
windowDeactivated(WindowEvent)
componentAdded(ContainerEvent)
componentRemoved(ContainerEvent)
mousePressed(MouseEvent)
mouseReleased(MouseEvent)
mouseClicked(MouseEvent)
mouseExited(MouseEvent)
mouseEntered(MouseEvent)
keyPressed(KeyEvent)
keyReleased(KeyEvent)
keyTypeed(KeyEvent)
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java.awt.event.ActionEvent
java.util.EventObject
+getSource(): Object
Returns the object on which the event initially occurred.
java.awt.event.AWTEvent
java.awt.event.ActionEvent
+getActionCommand(): String
Returns the command string associated with this action. For a
button, its text is the command string.
+getModifiers(): int
Returns the modifier keys held down during this action event.
+getWhen(): long
Returns the timestamp when this event occurred. The time is
the number of milliseconds since January 1, 1970, 00:00:00
GMT.
SimpleEventDemo
Run
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Inner Class Listeners
A listener class is designed specifically to
create a listener object for a GUI
component (e.g., a button). It will not be
shared by other applications. So, it is
appropriate to define the listener class
inside the frame class as an inner class.
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Inner Classes
Inner class: A class is a member of another class.
Advantages: In some applications, you can use an
inner class to make programs simple.

An inner class can reference the data and
methods defined in the outer class in which it
nests, so you do not need to pass the reference
of the outer class to the constructor of the inner
class.
ShowInnerClass
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Inner Classes, cont.
public class Test {
...
}
// OuterClass.java: inner class demo
public class OuterClass {
private int data;
/** A method in the outer class */
public void m() {
// Do something
}
public class A {
...
}
(a)
// An inner class
class InnerClass {
/** A method in the inner class */
public void mi() {
// Directly reference data and method
// defined in its outer class
data++;
m();
}
}
public class Test {
...
// Inner class
public class A {
...
}
}
(b)
}
(c)
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Inner Classes (cont.)
 Inner
classes can make programs simple
and concise.
 An
inner class supports the work of its
containing outer class and is compiled
into a class named
OuterClassName$InnerClassName.class.
For example, the inner class InnerClass in
OuterClass is compiled into
OuterClass$InnerClass.class.
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Revisiting SimpleEventDemo
Using Inner Classes
SimpleEventDemoInnerClass
Run
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Anonymous Inner Classes




An anonymous inner class must always extend a superclass or
implement an interface, but it cannot have an explicit extends or
implements clause.
An anonymous inner class must implement all the abstract
methods in the superclass or in the interface.
An anonymous inner class always uses the no-arg constructor
from its superclass to create an instance. If an anonymous inner
class implements an interface, the constructor is Object().
An anonymous inner class is compiled into a class named
OuterClassName$n.class. For example, if the outer class Test
has two anonymous inner classes, these two classes are
compiled into Test$1.class and Test$2.class.
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Anonymous Inner Classes (cont.)
Inner class listeners can be shortened using anonymous
inner classes. An anonymous inner class is an inner
class without a name. It combines declaring an inner
class and creating an instance of the class in one step.
An anonymous inner class is declared as follows:
new SuperClassName/InterfaceName() {
// Implement or override methods in superclass or interface
// Other methods if necessary
}
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Revising SimpleEventDemo
Using Anonymous Inner Classes
AnonymousListenerClass
Run
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Example: Controlling Balls

Objective: Use buttons to enlarge or shrink a ball.
ControlBall
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Example: Handling Window Events

Objective: Demonstrate handling the window events.
Any subclass of the Window class can generate the
following window events: window opened, closing,
closed, activated, deactivated, iconified, and
deiconified. This program creates a frame, listens to
the window events, and displays a message to
indicate the occurring event.
TestWindowEvent
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MouseEvent
java.awt.event.InputEvent
+getWhen(): long
Returns the timestamp when this event occurred.
+isAltDown(): boolean
Returns whether or not the Alt modifier is down on this event.
+isControlDown(): boolean
Returns whether or not the Control modifier is down on this event.
+isMetaDown(): boolean
Returns whether or not the Meta modifier is down on this event
+isShiftDown(): boolean
Returns whether or not the Shift modifier is down on this event.
java.awt.event.MouseEvent
+getButton(): int
Indicates which mouse button has been clicked.
+getClickCount(): int
Returns the number of mouse clicks associated with this event.
+getPoint(): java.awt.Point
Returns a Point object containing the x and y coordinates.
+getX(): int
Returns the x-coordinate of the mouse point.
+getY(): int
Returns the y-coordinate of the mouse point.
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Handling Mouse Events

Java provides two listener interfaces,
MouseListener and MouseMotionListener,
to handle mouse events.

The MouseListener listens for actions such as
when the mouse is pressed, released, entered,
exited, or clicked.

The MouseMotionListener listens for
actions such as dragging or moving the
mouse.
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Handling Mouse Events
java.awt.event.MouseListener
+mousePressed(e: MouseEvent): void
Invoked when the mouse button has been pressed on the
source component.
+mouseReleased(e: MouseEvent): void
Invoked when the mouse button has been released on the
source component.
+mouseClicked(e: MouseEvent): void
Invoked when the mouse button has been clicked (pressed and
released) on the source component.
+mouseEntered(e: MouseEvent): void
Invoked when the mouse enters the source component.
+mouseExited(e: MouseEvent): void
Invoked when the mouse exits the source component.
java.awt.event.MouseMotionListener
+mouseDragged(e: MouseEvent): void
Invoked when a mouse button is moved with a button pressed.
+mouseMoved(e: MouseEvent): void
Invoked when a mouse button is moved without a button
pressed.
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Example: Moving Message Using
Mouse
Objective: Create a
program to display a
message in a panel.
You can use the
mouse to move the
message. The
message moves as
the mouse drags and
is always displayed
at the mouse point.
MoveMessageDemo
Run
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The Timer Class
Some non-GUI components can fire events. The javax.swing.Timer
class is a source component that fires an ActionEvent at a predefined
rate.
javax.swing.Timer
+Timer(delay: int, listener:
ActionListener)
Creates a Timer with a specified delay in milliseconds and an
ActionListener.
+addActionListener(listener:
ActionListener): void
Adds an ActionListener to the timer.
+start(): void
Starts this timer.
+stop(): void
Stops this timer.
+setDelay(delay: int): void
Sets a new delay value for this timer.
The Timer class can be used to control animations. For example, you
can use it to display a moving message.
AnimationDemo
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61
Chapter 16
Creating User Interfaces
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Motivations
A graphical user interface (GUI) makes a system
user-friendly and easy to use. Creating a GUI
requires creativity and knowledge of how GUI
components work. Since the GUI components in
Java are very flexible and versatile, you can create
a wide assortment of useful user interfaces.
Previous chapters briefly introduced several GUI
components. This chapter introduces the frequently
used GUI components in detail (see Figure 16.1).
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Components Covered in the Chapter
Introduces
the frequently used GUI components
Uses borders and icons
JButton
Component
Container
JComponent
AbstractButton
JCheckBox
JToggleButton
JRadioButton
JLabel
JTextArea
JTextComponent
JTextField
JPasswordField
JComboBox
JList
JScrollBar
JSlider
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Buttons
A button is a component that triggers an action event
when clicked. Swing provides regular buttons,
toggle buttons, check box buttons, and radio buttons.
The common features of these buttons are
generalized in javax.swing.AbstractButton.
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AbstractButton
javax.swing.JComponent
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
javax.swing.AbstractButton
-actionCommand: String
The action command of this button.
-text: String
The button’s text (i.e., the text label on the button).
-icon: javax.swing.Icon
The button’s default icon. This icon is also used as the "pressed" and
"disabled" icon if there is no explicitly set pressed icon.
-pressedIcon: javax.swing.Icon
The pressed icon (displayed when the button is pressed).
-rolloverIcon: javax.swing.Icon
The rollover icon (displayed when the mouse is over the button).
-mnemonic: int
The mnemonic key value of this button. You can select the button by
pressing the ALT key and the mnemonic key at the same time.
-horizontalAlignment: int
The horizontal alignment of the icon and text (default: CENTER).
-horizontalTextPosition: int
The horizontal text position relative to the icon (default: RIGHT).
-verticalAlignment: int
The vertical alignment of the icon and text (default: CENTER).
-verticalTextPosition: int
The vertical text position relative to the icon (default: CENTER).
-borderPainted: boolean
Indicates whether the border of the button is painted. By default, a regular
button’s border is painted, but the borders for a check box and a radio
button is not painted.
-iconTextGap: int
The gap between the text and the icon on the button (JDK 1.4).
-selected(): boolean
The state of the button. True if the check box or radio button is selected,
false if it's not.
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JButton
JButton inherits AbstractButton and provides several
constructors to create buttons.
javax.swing.AbstractButton
javax.swing.JButton
+JButton()
Creates a default button with no text and icon.
+JButton(icon: javax.swing.Icon)
Creates a button with an icon.
+JButton(text: String)
Creates a button with text.
+JButton(text: String, icon: Icon)
Creates a button with text and an icon.
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JButton Properties (inherited)
 text
 icon
 mnemonic
 horizontalAlignment
 verticalAlignment
 horizontalTextPosition
 verticalTextPosition
 iconTextGap
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Example: Using Buttons
Write a program that displays a
message on a panel and uses
two buttons, <= and =>, to move
the message on the panel to the
left or right.
ButtonDemo
Run
MessagePanel
JButton
JButton
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JCheckBox
JCheckBox inherits all the properties such as text, icon,
mnemonic, verticalAlignment, horizontalAlignment,
horizontalTextPosition, verticalTextPosition, and selected
from AbstractButton, and provides several constructors to
create check boxes.
javax.swing.AbstractButton
javax.swing.JToggleButton
javax.swing.JCheckBox
+JCheckBox()
Creates a default check box button with no text and icon.
+JCheckBox(text: String)
Creates a check box with text.
+JCheckBox(text: String, selected:
boolean)
Creates a check box with text and specifies whether the check box is
initially selected.
+JCheckBox(icon: Icon)
Creates a checkbox with an icon.
+JCheckBox(text: String, icon: Icon)
Creates a checkbox with text and an icon.
+JCheckBox(text: String, icon: Icon,
selected: boolean)
Creates a check box with text and an icon, and specifies whether the check
box is initially selected.
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Example: Using Check Boxes
Add three check boxes named
Centered, Bold, and Italic into
Example 16.1 to let the user
specify whether the message
is centered, bold, or italic.
ButtonDemo
CheckBoxDemo
CheckBoxDemo
Run
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JRadioButton
Radio buttons are variations of check boxes. They are
often used in the group, where only one button is
checked at a time.
javax.swing.AbstractButton
javax.swing.JToggleButton
javax.swing.JRadioButton
+JRadioButton()
Creates a default radio button with no text and icon.
+JRadioButton(text: String)
Creates a radio button with text.
+JRadioButton(text: String, selected:
boolean)
Creates a radio button with text and specifies whether the radio button is
initially selected.
+JRadioButton(icon: Icon)
Creates a radio button with an icon.
+JRadioButton(text: String, icon: Icon)
Creates a radio button with text and an icon.
+JRadioButton(text: String, icon: Icon,
selected: boolean)
Creates a radio button with text and an icon, and specifies whether the radio
button is initially selected.
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Grouping Radio Buttons
ButtonGroup btg = new ButtonGroup();
btg.add(jrb1);
btg.add(jrb2);
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Example: Using Radio Buttons
Add three radio buttons
named Red, Green, and
Blue into the preceding
example to let the user
choose the color of the
message.
ButtonDemo
CheckBoxDemo
RadioButtonDemo
RadioButtonDemo
Run
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JLabel
A label is a display area for a short text, an image, or both.
javax.swing.JComponent
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
javax.swing.JLabel
-text: String
The label’s text.
-icon: javax.swing.Icon
The label’s image icon.
-horizontalAlignment: int
The horizontal alignment of the text and icon on the label.
-horizontalTextPosition: int
The horizontal text position relative to the icon on the label.
-verticalAlignment: int
The vertical alignment of the text and icon on the label.
-verticalTextPosition: int
The vertical text position relative to the icon on the label.
-iconTextGap: int
The gap between the text and the icon on the label (JDK 1.4).
+JLabel()
Creates a default label with no text and icon.
+JLabel(icon: javax.swing.Icon)
Creates a label with an icon.
+JLabel(icon: Icon, hAlignment: int)
Creates a label with an icon and the specified horizontal alignment.
+JLabel(text: String)
Creates a label with text.
+JLabel(text: String, icon: Icon,
hAlignment: int)
Creates a label with text, an icon, and the specified horizontal alignment.
+JLabel(text: String, hAlignment: int)
Creates a label with text and the specified horizontal alignment.
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JLabel Properties
JLabel inherits all the properties from
JComponent and has many properties
similar to the ones in JButton, such as
text, icon, horizontalAlignment,
verticalAlignment,
horizontalTextPosition,
verticalTextPosition, and iconTextGap.
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Using Labels
// Create an image icon from image file
ImageIcon icon = new ImageIcon("image/grapes.gif");
// Create a label with text, an icon,
// with centered horizontal alignment
JLabel jlbl = new JLabel("Grapes", icon,
SwingConstants.CENTER);
// Set label's text alignment and gap between text and icon
jlbl.setHorizontalTextPosition(SwingConstants.CENTER);
jlbl.setVerticalTextPosition(SwingConstants.BOTTOM);
jlbl.setIconTextGap(5);
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JTextField
A text field is an input area where the user can type in
characters. Text fields are useful in that they enable the user to
enter in variable data (such as a name or a description).
javax.swing.text.JTextComponent
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
-text: String
The text contained in this text component.
-editable: boolean
Indicates whether this text component is editable (default: true).
javax.swing.JTextField
-columns: int
The number of columns in this text field.
-horizontalAlignment: int
The horizontal alignment of this text field (default: LEFT).
+JTextField()
Creates a default empty text field with number of columns set to 0.
+JTextField(column: int)
Creates an empty text field with specified number of columns.
+JTextField(text: String)
Creates a text field initialized with the specified text.
+JTextField(text: String, columns: int)
Creates a text field initialized with the specified text and columns.
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JTextField Methods

getText()
Returns the string from the text field. Inherited

setText(String text)
Puts the given string in the text field. Inherited

setEditable(boolean editable)
Enables or disables the text field to be edited. By default,
editable is true. Inherited

setColumns(int)
Sets the number of columns in this text field.
The length of the text field is changeable.
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Example: Using Text Fields
Add a text field to the
preceding example to
let the user set a new
message.
JFrame
ButtonDemo
CheckBoxDemo
TextFieldDemo
RadioButtonDemo
TextFieldDemo
Run
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JTextArea
If you want to let the user enter multiple lines of text, you cannot use
text fields unless you create several of them. The solution is to use
JTextArea, which enables the user to enter multiple lines of text.
javax.swing.text.JTextComponent
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
javax.swing.JTextArea
-columns: int
The number of columns in this text area.
-rows: int
The number of rows in this text area.
-tabSize: int
The number of characters used to expand tabs (default: 8).
-lineWrap: boolean
Indicates whether the line in the text area is automatically wrapped (default:
false).
-wrapStyleWord: boolean
Indicates whether the line is wrapped on words or characters (default: false).
+JTextArea()
Creates a default empty text area.
+JTextArea(rows: int, columns: int)
Creates an empty text area with the specified number of rows and columns.
+JTextArea(text: String)
Creates a new text area with the specified text displayed.
+JTextArea(text: String, rows: int, columns: int) Creates a new text area with the specified text and number of rows and columns.
Appends the string to text in the text area.
+append(s: String): void
+insert(s: String, pos: int): void
Inserts string s in the specified position in the text area.
+replaceRange(s: String, start: int, end: int):
void
Replaces partial text in the range from position start to end with string s.
+getLineCount(): int
Returns the actual number of lines contained in the text area.
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Example: Using Text Areas
 This
example gives a program that displays
an image in a label, a title in a label, and a
text in a text area.
JPanel
JFrame
-char token
+getToken
DescriptionPanel
+setToken
+paintComponet
-jlblImage: JLabel
+mouseClicked
-jtaTextDescription: JTextArea
-char token
1
1
+getToken
TextAreaDemo
+setToken
+paintComponet
+mouseClicked
+setImageIcon(icon: ImageIcon): void
+setTitle(title: String): void
+setTextDescription(text: String): void
+getMinimumSize(): Dimension
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Example, cont.
TextAreaDemo
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JComboBox
A combo box is a simple list of items from which the user can
choose. It performs basically the same function as a list, but
can get only one value.
javax.swing.JComponent
javax.swing.JComboBox
+JComboBox()
Creates a default empty combo box.
+JComboBox(items: Object[])
Creates a combo box that contains the elements in the specified array.
+addItem(item: Object): void
Adds an item to the combo box.
+getItemAt(index: int): Object
Returns the item at the specified index.
+getItemCount(): int
Returns the number of items in the combo box.
+getSelectedIndex(): int
Returns the index of the selected item.
+setSelectedIndex(index: int): void
Sets the selected index in the combo box.
+getSelectedItem(): Object
Returns the selected item.
+setSelectedItem(item: Object): void
Sets the selected item in the combo box.
+removeItem(anObject: Object): void Removes an item from the item list.
Removes the item at the specified index in the combo box.
+removeItemAt(anIndex: int): void
+removeAllItems(): void
Removes all items in the combo box.
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JComboBox Methods
To add an item to a JComboBox jcbo, use
jcbo.addItem(Object item)
To get an item from JComboBox jcbo, use
jcbo.getItem()
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Using the
itemStateChanged Handler
When a choice is checked or unchecked,
itemStateChanged() for ItemEvent is
invoked as well as the actionPerformed()
handler for ActionEvent.
public void itemStateChanged(ItemEvent e) {
// Make sure the source is a combo box
if (e.getSource() instanceof JComboBox)
String s = (String)e.getItem();
}
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Example: Using Combo Boxes
This example lets
users view an
image and a
description of a
country's flag by
selecting the
country from a
combo box.
ComboBoxDemo
Run
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JList
A list is a component that performs basically the same function as a combo
box, but it enables the user to choose a single value or multiple values.
javax.swing.JComponent
javax.swing.JList
+JList()
Creates a default empty list.
+JList(items: Object[])
Creates a list that contains the elements in the specified array.
+getSelectedIndex(): int
Returns the index of the first selected item.
+setSelectedIndex(index: int): void
Selects the cell at the specified index.
+getSelectedIndices(): int[]
Returns an array of all of the selected indices in increasing order.
+setSelectedIndices(indices: int[]): void Selects the cells at the specified indices.
+getSelectedValue(): Object
Returns the first selected item in the list.
+getSelectedValues(): Object[]
Returns an array of the values for the selected cells in increasing index order.
+getVisibleRowCount(): int
Returns the number of visible rows displayed without a scrollbar. (default: 8)
+setVisibleRowCount(count: int): void
Sets the preferred number of visible rows displayed without a scrollbar.
+getSelectionBackground(): Color
Returns the background color of the selected cells.
+setSelectionBackground(c: Color): void Sets the background color of the selected cells.
+getSelectionForeground(): Color
Returns the foreground color of the selected cells.
+setSelectionForeground(c: Color): void Sets the foreground color of the selected cells.
+getSelectionMode(): int
Returns the selection mode for the list.
+setSelectionMode(selectionMode: int): Sets the selection mode for the list.
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Example: Using Lists
This example gives
a program that lets
users select
countries in a list
and display the flags
of the selected
countries in the
labels.
ListDemo
Run
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JScrollBar
A scroll bar is a control that enables the user to select from a range of values. The
scrollbar appears in two styles: horizontal and vertical.
javax.swing.JComponent
The get and set methods for these data fields are provided in
the class, but omitted in the UML diagram for brevity.
javax.swing.JScrollBar
-orientation: int
Specifies horizontal or vertical style, default is horizontal.
-maximum: int
Specifies the maximum value the scroll bar represents when the bubble
reaches the right end of the scroll bar for horizontal style or the
bottom of the scroll bar for vertical style.
-minimum: int
Specifies the minimum value the scroll bar represents when the bubble
reaches the left end of the scroll bar for horizontal style or the top of
the scroll bar for vertical style.
-visibleAmount: int
Specifies the relative width of the scroll bar's bubble. The actual width
appearing on the screen is determined by the maximum value and the
value of visibleAmount.
-value: int
Represents the current value of the scroll bar.
-blockIncrement: int
Specifies value added (subtracted) when the user activates the blockincrement (decrement) area of the scroll bar, as shown in Figure
13.30.
-unitIncrement: int
Specifies the value added (subtracted) when the user activates the unitincrement (decrement) area of the scroll bar, as shown in Figure
13.30.
+JScrollBar()
Creates a default vertical scroll bar.
+JScrollBar(orientation: int)
Creates a scroll bar with the specified orientation.
+JScrollBar(orientation: int, value: Creates a scrollbar with the specified orientation, value, extent,
int, extent: int, min: int, max: int)
minimum, and maximum.
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Scroll Bar Properties
Minimal value
Maximal value
Block decrement
Block increment
Bubble
Unit decrement
Unit increment
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Example: Using Scrollbars
This example uses
horizontal and vertical
scrollbars to control a
message displayed on a
panel. The horizontal
scrollbar is used to move
the message to the left or
the right, and the vertical
scrollbar to move it up and
down.
ScrollBarDemo
Run
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