fondamenti di java introduzione alla costruzione di gui (graphic user interface)
TRANSCRIPT
Fondamenti di Java
Introduzione alla costruzione di GUI (graphic user interface)
component - container - layout
Un Container contiene [0 o +] ComponentsIl Layout specifica come i Components sono disposti nel
ContainerUn 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
ScrollbarList Label
TextArea TextField
awt container hierarchy Container
Frame
Window
Dialog
FileDialog
ScrollPanelPanel
Applet
javax.swing
java.awt
Swing component hierarchy
Container
JComponent
Swing “containers”
JPanel
Swing “components”
JButton
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 Apppackage 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() { // aggiungere qui: set look&feel (vedi oltre)
this.setupGraphicEnvironment(); }
class Appprivate 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 finestra.setVisible(true); }}
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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
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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.
void actionPerformed(ActionEvent e) Invoked when an action occurs
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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.
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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 …public Object getSource()
Returns The object on which the Event initially occurred.
Seconda applicazione
ButtonPanel PainterJFrame
ActionListenerJPanel
ButtonaddActionListener
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Esempiopackage 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); Painter azioneRosso = new Painter(Color.RED,this); button1.addActionListener(azioneGiallo);
button2.addActionListener(azioneVerde); button3.addActionListener(azioneRosso); }
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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); } }
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Esempio 2public 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()); f.setSize(300,300); f.setVisible(true); }}
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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); } }
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Esempio 3public 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); b.setActionCommand(c[i]); } }
NON CONSIGLIATO – LAYOUT NON LIQUIDO!
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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
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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 Mouse Motion Events
the mouse is moved the mouse is dragged
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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&Feelpublic 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&Feelpublic 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. }
UIManager.getSystemLookAndFeelClassName(String s) Specifies the look and feel for the platform described by “s”.
Available Look&Feel"com.sun.java.swing.plaf.gtk.GTKLookAndFeel"
Specifies the GTK+ look and feel. Introduced in release 1.4.2.
"javax.swing.plaf.metal.MetalLookAndFeel" Specifies the Java look and feel.
"com.sun.java.swing.plaf.windows.WindowsLookAndFeel" Specifies the Windows look and feel. Currently, you can use this look and feel only on Microsoft Windows systems.
"com.sun.java.swing.plaf.motif.MotifLookAndFeel" Specifies the CDE/Motif look and feel. This look and feel can be used on any platform.