AWT to Swing
Java Swing
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AWT: Abstract Windowing Toolkit
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Swing: new with Java2
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API:
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GUI Component API
import java.awt.*
import javax.swing.*
Extends AWT
Many new improved components
Standard dialog boxes, tooltips, …
Look-and-feel, skins
Event listeners
http://java.sun.com/j2se/1.3/docs/api/index.html
Using a GUI Component
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Java: GUI component = class
1.
Create it
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Properties
2.
Configure it
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JButton
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Methods
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Add it
4.
Listen to it
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Events
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Anatomy of an Application GUI
GUI
JFrame
JPanel
JFrame
JButton
2.
3.
4.
containers
5.
JPanel
panel.add(b);
[avoided in java]
JButton
Events: Listeners
Using a GUI Component 2
1.
Internal structure
Properties: b.text = “press me”;
Methods:
b.setText(“press me”);
3.
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Instantiate object: b = new JButton(“press me”);
Create it
Configure it
Add children (if container)
Add to parent (if not JFrame)
Listen to it
order
important
JLabel
JButton
JLabel
1
Build from bottom up
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Create:
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Frame
Panel
Components
Listeners
JLabel
Add: (bottom up)
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Code
Listener
JFrame f = new JFrame(“title”);
JPanel p = new JPanel( );
JButton b = new JButton(“press me”);
JButton
p.add(b);
// add button to panel
f.setContentPane(p); // add panel to frame
JPanel
listeners into components
components into panel
panel into frame
f.show();
press me
JFrame
Application Code
Layout Managers
import javax.swing.*;
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class hello {
public static void main(String[] args){
JFrame f = new JFrame(“title”);
JPanel p = new JPanel();
JButton b = new JButton(“press me”);
„
Automatically control placement of
components in a panel
Why?
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p.add(b);
f.setContentPane(p);
// add button to panel
// add panel to frame
f.show();
press me
}
}
Layout Manager Heuristics
null
none,
programmer
sets x,y,w,h
FlowLayout
Layout Manager Heuristics
GridLayout
BorderLayout
n
Left to right,
Top to bottom
w
c
e
CardLayout
One at a time
GridBagLayout
JButton
s
2
Coordinate System
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Component Hierarchy
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Upside-down Cartesian
Each component has its own subwindow
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(0,0)
(width,0)
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Subwindow = rectangular area within parent component
Has own coordinate system
Clipping:
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Can’t paint outside its subwindow
Can’t paint over child components?
JPanel
(0,0)
(0,height)
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(width, height)
JButton
(0,0)
JButton
(wb, hb)
Ywindow = height - Ycartesian
(wp, hp)
Combinations
Combinations
JButton
JButton
JFrame
JButton JButton
n
JPanel: FlowLayout
JPanel: BorderLayout
JTextArea
c
JTextArea
Code: null layout
Code: FlowLayout
JFrame f = new JFrame(“title”);
JPanel p = new JPanel( );
JButton b = new JButton(“press me”);
b.setBounds(new Rectangle(10,10, 100,50));
p.setLayout(null);
// x,y layout
p.add(b);
f.setContentPane(p);
press me
JFrame f =
JPanel p =
FlowLayout
JButton b1
JButton b2
new JFrame(“title”);
new JPanel( );
L = new FlowLayout( );
= new JButton(“press me”);
= new JButton(“then me”);
p.setLayout(L);
p.add(b1);
p.add(b2);
f.setContentPane(p);
press me then me
Set layout mgr before adding components
3
Applets
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Applet Methods
JApplet is like a JFrame
Already has a panel
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JApplet
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Access panel with JApplet.getContentPane( )
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contentPane
import javax.swing.*;
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class hello extends JApplet {
public void init(){
JButton b = new JButton(“press me”);
getContentPane().add(b);
}
}
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JButton
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Called by browser:
init( )
start( )
stop( )
destroy( )
paint( )
Application + Applet
import javax.swing.*;
class helloApp {
public static void main(String[] args){
// create Frame and put my mainPanel in it
JFrame f = new JFrame(“title”);
mainPanel p = new mainPanel();
f.setContentPane(p);
f.show();
}
}
Command line
Browser
JFrame
JApplet
contentPane
class helloApplet extends JApplet {
public void init(){
// put my mainPanel in the Applet
mainPanel p = new mainPanel();
getContentPane().add(p);
}
}
// my main GUI is in here:
class mainPanel extends JPanel {
mainPanel(){
setLayout(new FlowLayout());
JButton b = new JButton(“press me”);
add(b);
}
}
Applet Security
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or
- initialization
- resume processing (e.g. animations)
- pause
- cleanup
- redraw stuff (‘expose’ event)
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No read/write on client machine
Cannot execute programs on client
machine
Communicate only with server
“Java applet window” Warning
JPanel
JButton
4