Fondamenti di Java
Introduzione alla
component - container - layout
Un Container contiene [0 o +] Components
Il Layout specifica come i Components sono disposti nel Container Un Container è un Component (quindi il contenimento è ricorsivo) Un Component ha una Graphics associata
Component
Container
posiziona Layout
Graphics
awt component hierarchy
Component
Button Canvas Checkbox Choice TextComponent
awt container hierarchy
Container
Frame
Window
Dialog
FileDialog
ScrollPanel Panel
Applet
javax.swing
java.awt
Swing component hierarchy
Container
JComponent
Component
Top Level Containers
TUTORIAL:
http://java.sun.com/docs/books/tutorial/uiswing/
General Purpose Containers
Special Purpose Containers
Basic Controls
Uneditable Information
More complex structures
Prima applicazione
App YellowWindow
JFrame
JFrame
class YellowWindow
package it.unitn.science.prog2.guiApp;
import java.awt.*; import javax.swing.*;
public class YellowWindow extends JFrame
{
private JPanel contentPane;
public YellowWindow()
{
try { jbInit(); } catch(Exception e) { e.printStackTrace(); }
}
private void jbInit() throws Exception
{
contentPane=(JPanel)this.getContentPane();
this.setSize(new Dimension(400, 300));
contentPane.setBackground(Color.YELLOW);
}
}
class App
package it.unitn.science.prog2.guiApp;
import javax.swing.*;
import java.awt.*;
public class App
{
JFrame finestra=null;
public static void main(String[ ] a){
new App();
}
public App() {
class App
private void setupGraphicEnvironment() {
finestra = new YellowWindow(); //new CalculatorWindow
// trova le dimensioni dello schermo e della finestra
Dimension screenSize =
Toolkit.getDefaultToolkit().getScreenSize();
Dimension frameSize = finestra.getSize();
// assicurati che la finestra non sia più grande dello schermo
if (frameSize.height > screenSize.height)
frameSize.height = screenSize.height;
if (frameSize.width > screenSize.width)
frameSize.width = screenSize.width;
class App
// centra la finestra nello schermo
finestra.setLocation((screenSize.width - frameSize.width) / 2,
(screenSize.height - frameSize.height) / 2);
// fai in modo che la chiusura della finestra
// termini l'applicazione
finestra.setDefaultCloseOperation(JFrame. EXIT_ON_CLOSE );
// rendi la finestra visibile
18
Event Listeners
Some Events and Their Associated Event Listeners
Act that Results in the Event Listener Type User clicks a button, presses Enter while typing
in a text field, or chooses a menu item ActionListener User closes a frame (main window) WindowListener User presses a mouse button while the cursor is
over a component MouseListener
User moves the mouse over a component MouseMotionListener
Component becomes visible ComponentListener
Component gets the keyboard focus FocusListener
Table or list selection changes ListSelectionListener Any property in a component changes such as
the text on a label PropertyChangeListener
19
ActionListener
public interface ActionListener extends EventListener
The listener interface for receiving action events. The
class that is interested in processing an action event
implements this interface, and the object created with
that class is registered with a component, using the
component's addActionListener method.
20
ActionEvent
ActionEvent extends AWTEvent
A semantic event which indicates that a component-
defined action occured. This high-level event is
generated by a component (such as a Button) when
the component-specific action occurs (such as being
pressed). The event is passed to every every
ActionListener object that registered to receive such
events using the component's addActionListener
method.
21
ActionEvent
Method Summary
String getActionCommand()
Returns the command string associated with this action.
int getModifiers()
Returns the modifier keys held down during this action event.
long getWhen()
Returns the timestamp of when this event occurred.
String paramString()
Returns a parameter string identifying this action event.
Methods Inherited
Seconda applicazione
ButtonPanel Painter
JFrame
ActionListener
JPanel
Button
addActionListener
3
23
Esempio
package actionlistener;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.JFrame;
public class ButtonPanel extends JPanel { public ButtonPanel() {
super();
JButton button1 = new JButton("Giallo");
JButton button2 = new JButton("Verde");
JButton button3 = new JButton("Rosso");
this.add(button1);
this.add(button2);
this.add(button3);
Painter azioneGiallo = new Painter(Color.YELLOW,this);
Painter azioneVerde = new Painter( Color.GREEN,this);
24
Esempio - continua
public static void main(String a[]) { JFrame f=new JFrame();
f.setContentPane(new ButtonPanel());
f.setSize(300,300);
f.setVisible(true);
}
}
class Painter implements ActionListener { private Color colore;
private JPanel contenitore;
public Painter(Color colore, JPanel contenitore) { this.colore = colore;
this.contenitore=contenitore;
}
public void actionPerformed(ActionEvent actionEvent) { contenitore.setBackground(colore);
} }
25
Esempio 2
public class ButtonPanel extends JPanel { public ButtonPanel() {
super();
Painter p=new Painter(this);
String c[]={"Giallo","Verde","Rosso"};
for (int i=0;i<c.length;i++) { JButton b=new JButton(c[i]);
this.add(b);
b.addActionListener(p);
// b.setActionCommand(c[i]);
} }
public static void main(String a[]) { JFrame f=new JFrame();
f.setContentPane(new ButtonPanel());
26
Esempio 2 - continua
class Painter implements ActionListener { private JPanel contenitore;
private Color colore;
public Painter(JPanel contenitore) { this.contenitore=contenitore;
}
public void actionPerformed(ActionEvent actionEvent) { String s=((JButton)actionEvent.getSource()).getText();
//String s=actionEvent.getActionCommand();
if (s.equals("Giallo")) colore=Color.YELLOW;
else if (s.equals("Rosso")) colore=Color.RED;
else if (s.equals("Verde")) colore=Color.GREEN;
contenitore.setBackground(colore);
} }
27
Esempio 3
public class ButtonPanel extends JPanel { public ButtonPanel() {
super();
Painter p=new Painter(this);
this.setLayout(null);
String c[]={"Giallo","Verde","Rosso"};
for (int i=0;i<c.length;i++) { JButton b=new JButton(c[i]);
b.setSize(100,50);
b.setLocation(i*100,i*50);
this.add(b);
b.addActionListener(p);
28
Compito
Scrivere un applicazione contenente un bottone
che quando viene premuto si sposta altrove
nella finestra.
Scrivere una applicazione contenente due
bottoni: uno ingrandisce la dimensione della
finestra, l’altro la rimpicciolisce
29
Mouse events
This low-level event is generated by a component object
for:
Mouse Events
a mouse button is pressed
a mouse button is released
a mouse button is clicked (pressed and released)
the mouse cursor enters the unobscured part of
component's geometry
the mouse cursor exits the unobscured part of
component's geometry
30
Compito
Scrivere un applicazione contenente un TextField
il cui valore inizialmente è zero, e che viene
incrementato di uno ogni volta che il bottone
del mouse viene cliccato.
Scrivere un’applicazione contenente un bottone
che si posiziona dove viene cliccato il bottone
del mouse. Se invece viene cliccato il bottone
grafico, questo si riposiziona nella sua sede
iniziale.
Pluggable Look&Feel
Scelta del Look&Feel
public static void main(String[] args) {
try {
UIManager.setLookAndFeel(
UIManager.getCrossPlatformLookAndFeelClassName());
} catch (Exception e) { }
new SwingApplication(); //Create and show the GUI.
}
UIManager.getCrossPlatformLookAndFeelClassName()
Returns the Java look and feel.
UIManager.getSystemLookAndFeelClassName()
Specifies the look and feel for the current platform.
Scelta del Look&Feel
public static void main(String[] args) {
try {
UIManager.setLookAndFeel(
"com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
} catch (Exception e) { }
new SwingApplication(); //Create and show the GUI.
}
Available Look&Feel
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