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swing:window_events [2015/05/16 21:32] gthanos |
swing:window_events [2016/02/26 11:15] |
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- | ====== Window Events & Window Listeners ====== | ||
- | |||
- | Σε όλα τα προηγούμενα παραδείγματα χρησιμοποιήσαμε την μέθοδο //setDefaultCloseOperation// για τον προσδιορισμό της default συμπεριφοράς κατά το πάτημα του εικονιδίου που συνδέεται με το παράθυρο, όπως παρακάτω: | ||
- | <code java> | ||
- | frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); | ||
- | </code> | ||
- | |||
- | Στην πραγματικότητα αυτό που συμβαίνει κάθε φορά που πατάτε ένα από τα κουμπιά που συνδέονται με την λειτουργία του παραθύρου (στο δεξιό ή το αριστερό επάνω μέρος του παραθύρου - εξαρτάται από το λειτουργικό σύστημα) είναι ότι παράγεται ένα [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/WindowEvent.html|WindowEvent]]. Ένα //event// αυτού του τύπου μπορείτε να το λάβετε φτιάχνοντας ένα αντικείμενο του τύπου [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/WindowListener.html|WindowListener]] και συνδέοντας το JFrame του παραθύρου με το αντικείμενο αυτό μέσω της μεθόδου //setWindowListener()//. Οι μέθοδοι του interface //WindowListener// είναι οι παρακάτω: | ||
- | |||
- | <code java> | ||
- | void windowActivated(WindowEvent e) | ||
- | //Invoked when the Window is set to be the active Window. | ||
- | |||
- | void windowClosed(WindowEvent e) | ||
- | //Invoked when a window has been closed as the result of calling dispose on the window. | ||
- | |||
- | void windowClosing(WindowEvent e) | ||
- | //Invoked when the user attempts to close the window from the window's system menu. | ||
- | |||
- | void windowDeactivated(WindowEvent e) | ||
- | //Invoked when a Window is no longer the active Window. | ||
- | |||
- | void windowDeiconified(WindowEvent e) | ||
- | //Invoked when a window is changed from a minimized to a normal state. | ||
- | |||
- | void windowIconified(WindowEvent e) | ||
- | //Invoked when a window is changed from a normal to a minimized state. | ||
- | |||
- | void windowOpened(WindowEvent e) | ||
- | //Invoked the first time a window is made visible. | ||
- | </code> | ||
- | |||
- | Όταν πατάτε το εικονίδιο σμίκρυνσης του παραθύρου ή πατάτε το συνδυασμό πλήκτρων //ALT+TAB// τότε παράθυρο φεύγει από το προσκήνιο. Αντίστοιχα, αν το επιλέξετε και πάλι ή αν πατήσετε ξανά //ALT+TAB// τότε το παράθυρο επανέρχεται. Στην πρώτη περίπτωση, το παράθυρο έχασε το focus, ενώ στην δεύτερη το ανάκτησε. Για την παρακολούθηση των γεγονότων αυτών υπάρχει ένας επιπλέον τύπος Listener, o [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/WindowFocusListener.html|WindowFocusListener]] που λαμβάνει την μεταβολή των παραπάνω δύο καταστάσεων κάθε παραθύρου. Οι μέθοδοι που υποστηρίζει ο παραπάνω τύπος Listener είναι οι παρακάτω. | ||
- | <code java> | ||
- | void windowGainedFocus(WindowEvent e) | ||
- | //Invoked when the Window is set to be the focused Window, which means that the Window, or one of its subcomponents, will receive keyboard events. | ||
- | void windowLostFocus(WindowEvent e) | ||
- | //Invoked when the Window is no longer the focused Window, which means that keyboard events will no longer be delivered to the Window or any of its subcomponents. | ||
- | </code> | ||
- | |||
- | Δείτε το παρακάτω παράδειγμα το οποίο συνοψίζει την χρήση των παραπάνω δύο interfaces. | ||
- | <code java> | ||
- | package events; | ||
- | |||
- | import java.awt.*; | ||
- | import java.awt.event.*; | ||
- | import javax.swing.*; | ||
- | |||
- | public class WindowEventDemo extends JFrame | ||
- | implements WindowListener, | ||
- | WindowFocusListener { | ||
- | static final String newline = System.getProperty("line.separator"); | ||
- | static final String space = " "; | ||
- | static WindowEventDemo frame = new WindowEventDemo("WindowEventDemo"); | ||
- | JTextArea display; | ||
- | | ||
- | public static void main(String[] args) { | ||
- | /* Use an appropriate Look and Feel */ | ||
- | try { | ||
- | //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); | ||
- | //UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel"); | ||
- | UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel"); | ||
- | } catch (UnsupportedLookAndFeelException ex) { | ||
- | ex.printStackTrace(); | ||
- | } catch (IllegalAccessException ex) { | ||
- | ex.printStackTrace(); | ||
- | } catch (InstantiationException ex) { | ||
- | ex.printStackTrace(); | ||
- | } catch (ClassNotFoundException ex) { | ||
- | ex.printStackTrace(); | ||
- | } | ||
- | /* Turn off metal's use of bold fonts */ | ||
- | UIManager.put("swing.boldMetal", Boolean.FALSE); | ||
- | | ||
- | //Schedule a job for the event dispatch thread: | ||
- | //creating and showing this application's GUI. | ||
- | javax.swing.SwingUtilities.invokeLater(new Runnable() { | ||
- | public void run() { | ||
- | createAndShowGUI(); | ||
- | } | ||
- | }); | ||
- | } | ||
- | | ||
- | /** | ||
- | * Create the GUI and show it. For thread safety, | ||
- | * this method should be invoked from the | ||
- | * event-dispatching thread. | ||
- | */ | ||
- | | ||
- | private static void createAndShowGUI() { | ||
- | //Create and set up the window. | ||
- | frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE); | ||
- | | ||
- | //Set up the content pane. | ||
- | frame.addComponentsToPane(); | ||
- | | ||
- | //Display the window. | ||
- | frame.pack(); | ||
- | frame.setVisible(true); | ||
- | } | ||
- | | ||
- | private void addComponentsToPane() { | ||
- | display = new JTextArea(); | ||
- | display.setEditable(false); | ||
- | JScrollPane scrollPane = new JScrollPane(display); | ||
- | scrollPane.setPreferredSize(new Dimension(500, 450)); | ||
- | getContentPane().add(scrollPane, BorderLayout.CENTER); | ||
- | | ||
- | addWindowListener(this); | ||
- | addWindowFocusListener(this); | ||
- | } | ||
- | | ||
- | public WindowEventDemo(String name) { | ||
- | super(name); | ||
- | } | ||
- | | ||
- | public void windowClosing(WindowEvent e) { | ||
- | displayMessage("WindowListener method called: windowClosing."); | ||
- | //A pause so user can see the message before | ||
- | //the window actually closes. | ||
- | ActionListener task = new ActionListener() { | ||
- | boolean alreadyDisposed = false; | ||
- | public void actionPerformed(ActionEvent e) { | ||
- | if (frame.isDisplayable()) { | ||
- | alreadyDisposed = true; | ||
- | frame.dispose(); | ||
- | } | ||
- | } | ||
- | }; | ||
- | Timer timer = new Timer(500, task); //fire every half second | ||
- | timer.setInitialDelay(2000); //first delay 2 seconds | ||
- | timer.setRepeats(false); | ||
- | timer.start(); | ||
- | } | ||
- | | ||
- | public void windowClosed(WindowEvent e) { | ||
- | //This will only be seen on standard output. | ||
- | displayMessage("WindowListener method called: windowClosed."); | ||
- | } | ||
- | | ||
- | public void windowOpened(WindowEvent e) { | ||
- | displayMessage("WindowListener method called: windowOpened."); | ||
- | } | ||
- | | ||
- | public void windowIconified(WindowEvent e) { | ||
- | displayMessage("WindowListener method called: windowIconified."); | ||
- | } | ||
- | | ||
- | public void windowDeiconified(WindowEvent e) { | ||
- | displayMessage("WindowListener method called: windowDeiconified."); | ||
- | } | ||
- | | ||
- | public void windowActivated(WindowEvent e) { | ||
- | displayMessage("WindowListener method called: windowActivated."); | ||
- | } | ||
- | | ||
- | public void windowDeactivated(WindowEvent e) { | ||
- | displayMessage("WindowListener method called: windowDeactivated."); | ||
- | } | ||
- | | ||
- | public void windowGainedFocus(WindowEvent e) { | ||
- | displayMessage("WindowFocusListener method called: windowGainedFocus."); | ||
- | } | ||
- | | ||
- | public void windowLostFocus(WindowEvent e) { | ||
- | displayMessage("WindowFocusListener method called: windowLostFocus."); | ||
- | } | ||
- | | ||
- | private void displayMessage(String msg) { | ||
- | display.append(msg + newline); | ||
- | System.out.println(msg); | ||
- | } | ||
- | } | ||
- | </code> | ||
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