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The Java Foundation Classes (JFC) are a set
of packages encompassing the following
APIs:
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Abstract Window Toolkit (AWT): native GUI
components
Swing: lightweight GUI components
2D: rendering two-dimensional shapes, text, and
images
Accessibility: allowing compatibility with, for
example, screen readers and screen magnifiers
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Provides basic UI components:
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Buttons, lists, menus, textfields, etc
Event handling mechanism
Clipboard and data transfer
Image manipulation
Font manipulation
Graphics
Platform independence is achieved through
peers, or native GUI components
java.awt
java.awt.accessibility
java.awt.color
java.awt.datatransfer
java.awt.dnd
java.awt.event
java.awt.font
java.awt.geom
java.awt.im
java.awt.image
java.awt.peer
java.awt.print
java.awt.swing
Basic component functionality
Assistive technologies
Colors and color spaces
Clipboard and data transfer support
Drag and drop
Event classes and listeners
2D API font package
2D API geometry package
Input methods
Fundamental image manipulation classes
Peer interfaces for component peers
2D API support for printing
Swing components
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The first AWT (Java 1.0) was rolled out in an
incredible 6 weeks using peers
Thus an AWT menu on the Solaris platform,
for example, actually creates a Motif menu
object as its peer
UI components that have peers are called
heavyweight because
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they are rendered in their own (opaque) windows and
thus are expensive to use,
they must be rectangular and cannot have transparent
backgrounds, and
they are not amenable to being subclassed
Java
Program
Java
AWT
Native
Window
System
Peers
A Java program creates and displays an AWT component,
which creates and displays a native component, or peer.
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AWT 1.1 introduced the notion of lightweight
components which:
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are contained within a heavyweight component's
window
do not have peers
are rendered in their container's window rather
than one of their own
do not incur performance penalties and can have
transparent backgrounds
Almost all Swing components are
lightweight ones that extend either
java.awt.Component or
java.awt.Container
Object
Component
Container
JComponent
List
Window
Scrollbar
Scrollpane
Label
Canvas
Button
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Swing does not replace the AWT; it is built
on top of it
All 1.0 AWT components are heavyweight;
corresponding Swing components are
lightweight
Swing component names begin with ``J'':
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Component (AWT) vs. JComponent (Swing)
Button (AWT) vs. JButton (Swing)
Always use Swing components; however, since
Swing is built on top of AWT, you will need to
know some AWT methods
JComponent
AbstractButton
JButton
JLabel
JMenuItem
JToggleButto
n
JList
JScrollBar
JCheckBox
JFileChooser
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Note that JComponents are containers
JComponents do not extend their AWT
counterparts:
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For example, the JButton class is not a subclass
(direct or indirect) of Button
However, some Swing components are not
JComponents
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For example, some Swing containers are direct
subclasses of their AWT counterparts
Container
JComponent
Panel
ScrollPane
Window
Dialog
Applet
Frame
Container
JComponent
Panel
ScrollPane
Window
Dialog
Frame
Applet
JFrame
JApplet
JWindow
JDialog
JComponent
JLayeredPane
JPanel
JScrollPane
JDesktopPane
JInternalFrame
JTable
JTree
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void
void
void
void
void
void
void
setBackground(Color c)
setForeground(Color c)
setEnabled(boolean b)
setVisible(boolean b)
setFont(Font f)
setSize(Dimension d)
setLocation(int x, int y)
All but setSize and setLocation are overridden
by the JComponent class.
import java.awt.*;
import javax.swing.*;
public class SwingTest {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
frame.setVisible(true);
}
}
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setSize and setLocation require
java.awt.*; the rest require javax.swing.*
The JFrame constructor argument is used as a title
The Dimension constructor takes an integer width
and height, respectively
The setLocation method takes a pair of integer
coordinates (x,y) where (0,0) is the upper left corner of
the display
The visibility of a JFrame is set to false by default
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This window was managed by the K Desktop
Environment (KDE)
Clicking the Close button (X) will cause the
display to be hidden, but the program will
continue since no listeners are set up yet
Can use ctl-C to kill the Java Virtual Machine
The java.awt.Color class has the following static
fields (data members):
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Color.black
Color.blue
Color.cyan
Color.darkGray
Color.gray
Color.green
Color.lightGra
y
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Color.magenta
Color.orange
Color.pink
Color.red
Color.white
Color.yellow
import java.awt.*;
import javax.swing.*;
public class SwingTest {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
contentPane.setBackground(Color.red);
frame.setVisible(true);
}
}
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Q: Why not just: frame.setBackground(Color.red);
?
A: In order to be lightweight, Swing's top-level
window objects must be built on top of a
lightweight AWT Container object introduced
in version 1.1
This container is called a content pane
Swing top-level window classes:
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JWindow
JFrame
JApplet
JDialog
JInternalFrame
import java.awt.*;
import javax.swing.*;
public class SwingTest {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE IS A LABEL");
contentPane.add(label, BorderLayout.NORTH);
JButton button = new JButton("BUTTON");
contentPane.add(button, BorderLayout.SOUTH);
frame.setVisible(true);
}
}
Resized
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Since the frame is a top-level Swing
window, components must be added to its
content pane
When components are added to a container,
how they are placed is dependent upon the
container's layout manager
The default layout manager for a JFrame is a
BorderLayout manager (described later)
When adding to a container whose layout
manager is BorderLayout, the second
parameter should be a location defined in the
BorderLayout class
import java.awt.*;
import javax.swing.*;
public class SwingTest {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE IS A LABEL");
contentPane.add(label, BorderLayout.NORTH);
JButton button = new JButton("BUTTON");
contentPane.add(button, BorderLayout.SOUTH);
String[] options = {"Option 1", "Option 2",
"Option 3"};
JList list = new JList(options);
contentPane.add(list, BorderLayout.CENTER);
frame.setVisible(true);
}
}
Note that "Option 3" has been selected.
public class SwingTest {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(400,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE IS A LABEL");
contentPane.add(label, BorderLayout.NORTH);
JButton button = new JButton("BUTTON");
contentPane.add(button, BorderLayout.SOUTH);
String[] options = {"Option 1", "Option 2", "Option 3"};
JList list = new JList(options);
contentPane.add(list, BorderLayout.CENTER);
JCheckBox cbox = new JCheckBox("Check");
contentPane.add(cbox, BorderLayout.WEST);
JSlider slider = new JSlider();
contentPane.add(slider, BorderLayout.EAST);
frame.setVisible(true);
}
}
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A layout manager determines the location and
size of components placed into a container
Different layout managers use different
algorithms for determining size and location:
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BorderLayout: places at compass locations and center
FlowLayout: places components in rows, left to right
GridLayout: places in rectangular grid
BoxLayout: places in a single row or column
public class SwingTest {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
contentPane.setLayout(new FlowLayout());
JLabel label = new JLabel("HERE IS A LABEL");
JButton button = new JButton("BUTTON");
String[] options = {"Option 1", "Option 2", "Option 3"};
JList list = new JList(options);
JCheckBox cbox = new JCheckBox("Check");
JSlider slider = new JSlider();
contentPane.add(label);
contentPane.add(button);
contentPane.add(list);
contentPane.add(cbox);
contentPane.add(slider);
frame.setVisible(true);
}
}
Resized
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The default layout manager for content
panes is BorderLayout. Recall that the
following Swing components have content
panes:
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JWindow
JFrame
JDialog
JApplet
JInternalFrame
The other Swing container is the JPanel,
whose default layout manager is
FlowLayout.
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A JPanel object can be used for grouping
components into a container, which can then
be added to another container
The JPanel constructor with no arguments
creates a panel with a FlowLayout
manager
Another JPanel constructor takes any
layout manager as an argument
A JPanel can also be used a a blank area
for drawing custom graphics
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE ARE SOME BUTTONS",
SwingConstants.CENTER);
JButton button1 = new JButton("BUTTON1");
JButton button2 = new JButton("BUTTON2");
JButton button3 = new JButton("BUTTON3");
JPanel panel = new JPanel();
panel.add(button1);
panel.add(button2);
panel.add(button3);
contentPane.add(label, BorderLayout.NORTH);
contentPane.add(panel, BorderLayout.CENTER);
frame.setVisible(true);
Note use of SwingConstants.CENTER argument
in JLabel constructor.
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
JLabel label = new JLabel("HERE ARE SOME BUTTONS",
SwingConstants.CENTER);
JButton button1 = new JButton("BUTTON1");
JButton button2 = new JButton("BUTTON2");
JButton button3 = new JButton("BUTTON3");
JPanel panel = new JPanel();
panel.setLayout
(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.add(button1);
panel.add(button2);
panel.add(button3);
contentPane.add(label, BorderLayout.NORTH);
contentPane.add(panel, BorderLayout.CENTER);
frame.setVisible(true);
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The button panel is to the west because no
other component was placed there
The BoxLayout constructor requires both
the component being laid out and either:
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BoxLayout.X_AXIS
BoxLayout.Y_AXIS
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Some layout constructors allow hgap and
vgap, integers specifying the number of
pixels separating components horizontally
and vertically
FlowLayout allows the specification of
whether the line of components should be
left-justified, right-justified, or centered
new FlowLayout(int align)
new FlowLayout(int align, int hgap, int vgap)
new BorderLayout(int hgap, int vgap)
new GridLayout(int rows, int cols)
new GridLayout(int rows, int cols,
int hgap, int vgap)
JFrame frame = new JFrame("Test Frame");
frame.setSize(new Dimension(300,200));
frame.setLocation(100,100);
Container contentPane = frame.getContentPane();
LayoutManager lm = contentPane.getLayout();
((BorderLayout)lm).setHgap(25);
JLabel label = new JLabel("HERE ARE SOME BUTTONS",
SwingConstants.CENTER);
JButton button1 = new JButton("BUTTON1");
JButton button2 = new JButton("BUTTON2");
JButton button3 = new JButton("BUTTON3");
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.add(button1);
panel.add(button2);
panel.add(button3);
contentPane.add(label, BorderLayout.NORTH);
contentPane.add(panel, BorderLayout.CENTER);
frame.setVisible(true);
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The LayoutManager returned by
getLayout() is an interface type that the
BorderLayout class implements
The setHgap method we want is in the
BorderLayout class
So we must cast the LayoutManager to
BorderLayout in order to use setHgap
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Layout managers often need to resize their
components to make things fit
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For example, the widths and heights of
components in a BoxLayout are adjusted
according to both preferred and maximum heights
and widths
If you don't like the size of the components a
layout manager comes up with, you may
have to give sizing hints using the following
methods from the JComponent class:
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void setMinimumSize(Dimension d)
void setPreferredSize(Dimension d)
void setMaximumSize(Dimension d)