Fondamenti di Java. Introduzione alla costruzione di GUI (graphic user interface)

Transcription

1 Fondamenti di Java Introduzione alla costruzione di GUI (graphic user interface)

2 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 Graphics posiziona Layout Container

3 awt component hierarchy Component Button Canvas Checkbox Choice TextComponent List Scrollbar Label TextArea TextField

4 awt container hierarchy Container Panel Window ScrollPanel Applet Frame Dialog FileDialog

5 Swing component hierarchy Component Container java.awt JComponent javax.swing JPanel Swing containers JButton Swing components

6 Top Level Containers TUTORIAL:

7 General Purpose Containers

8 Special Purpose Containers

9 Basic Controls

10 Uneditable Information

11 More complex structures

12 Prima applicazione JFrame App YellowWindow

13 JFrame

14 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);

15 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() { // aggiungere qui: set look&feel (vedi oltre) this.setupgraphicenvironment();

16 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;

17 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);

18 18 Event Listeners Some Events and Their Associated Event Listeners Act that Results in the Event User clicks a button, presses Enter while typing in a text field, or chooses a menu item User closes a frame (main window) User presses a mouse button while the cursor is over a component User moves the mouse over a component Component becomes visible Component gets the keyboard focus Table or list selection changes Any property in a component changes such as the text on a label Listener Type ActionListener WindowListener MouseListener MouseMotionListener ComponentListener FocusListener ListSelectionListener PropertyChangeListener

19 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. void actionperformed(actionevent e) Invoked when an action occurs

20 20 ActionEvent ActionEvent extends AWTEvent A semantic event which indicates that a componentdefined 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 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 public Object getsource() Returns The object on which the Event initially occurred.

22 Seconda applicazione JPanel ActionListener JFrame ButtonPanel Painter 3 Button addactionlistener

23 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); Painter azionerosso = new Painter(Color.RED,this); button1.addactionlistener(azionegiallo); button2.addactionlistener(azioneverde); button3.addactionlistener(azionerosso);

24 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 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()); f.setsize(300,300); f.setvisible(true);

26 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 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); b.setactioncommand(c[i]); NON CONSIGLIATO LAYOUT NON LIQUIDO!

28 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 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 Mouse Motion Events the mouse is moved the mouse is dragged

30 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.

31 Pluggable Look&Feel

32 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.

33 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. UIManager.getSystemLookAndFeelClassName(String s) Specifies the look and feel for the platform described by s.

34 Available Look&Feel "com.sun.java.swing.plaf.gtk.gtklookandfeel" Specifies the GTK+ look and feel. Introduced in release "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.