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--- swing:window_events [2015/05/16 20:15]
gthanos
+++ swing:window_events [2016/02/26 11:15] (current)
@@ Line 29: / Line 29: @@
 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 (από το site της Oracle) το οποίο συνοψίζει την χρήση των παραπάνω δύο interfaces.
+<code java WindowEventDemo.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>

Αντικειμενοστραφής Προγραμματισμός, Εφαρμογές με χρήση της γλώσσας προγραμματισμού JAVA

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