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--- swing:jcheckbox [2020/03/30 07:29]
+++ swing:jcheckbox [2020/03/30 08:00]
gthanos
@@ Line 1: / Line 1: @@
+===== Η κλάση JCheckBox =====
+Ένα //check box// έχει δύο δυνατές καταστάσεις //α)// επιλεγμένο και //β)// απο-επιλεγμένο. Κάθε //check box// υλοποιείται από την κλάση [[https://docs.oracle.com/javase/7/docs/api/javax/swing/JCheckBox.html|JCheckBox]]. Δείτε το παρακάτω παράδειγμα χρήσης της κλάσης JCheckBox από το [[https://docs.oracle.com/javase/tutorial/uiswing/components/button.html|site της Oracle]].
+<code java CheckBoxDemo.java>
+import java.awt.*;
+import java.awt.event.*;
+import javax.swing.*;
+/*
+ * CheckBoxDemo.java requires 16 image files in the images/geek
+ * directory:
+ * geek-----.gif, geek-c---.gif, geek--g--.gif, geek---h-.gif, geek----t.gif,
+ * geek-cg--.gif, ..., geek-cght.gif.
+ */
+public class CheckBoxDemo extends JPanel {
+              //implements ItemListener {
+  JCheckBox chinButton;
+  JCheckBox glassesButton;
+  JCheckBox hairButton;
+  JCheckBox teethButton;
+  StringBuffer choices;
+  JLabel pictureLabel;
+  public CheckBoxDemo() {
+    super(new BorderLayout());
+    //Create the check boxes.
+    chinButton = new JCheckBox("Chin");
+    chinButton.setMnemonic(KeyEvent.VK_C);
+    chinButton.setSelected(true);
+    glassesButton = new JCheckBox("Glasses");
+    glassesButton.setMnemonic(KeyEvent.VK_G);
+    glassesButton.setSelected(true);
+    hairButton = new JCheckBox("Hair");
+    hairButton.setMnemonic(KeyEvent.VK_H);
+    hairButton.setSelected(true);
+    teethButton = new JCheckBox("Teeth");
+    teethButton.setMnemonic(KeyEvent.VK_T);
+    teethButton.setSelected(true);
+    //Register a listener for the check boxes.
+    chinButton.addItemListener(itemListener);
+    glassesButton.addItemListener(itemListener);
+    hairButton.addItemListener(itemListener);
+    teethButton.addItemListener(itemListener);
+    //Indicates what's on the geek.
+    choices = new StringBuffer("cght");
+    //Set up the picture label
+    pictureLabel = new JLabel();
+    pictureLabel.setFont(pictureLabel.getFont().deriveFont(Font.ITALIC));
+    updatePicture();
+    //Put the check boxes in a column in a panel
+    JPanel checkBoxPanel = new JPanel(new GridLayout(0, 1));
+    checkBoxPanel.add(chinButton);
+    checkBoxPanel.add(glassesButton);
+    checkBoxPanel.add(hairButton);
+    checkBoxPanel.add(teethButton);
+    add(checkBoxPanel, BorderLayout.LINE_START);
+    add(pictureLabel, BorderLayout.CENTER);
+    setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
+  }
+  ItemListener itemListener = new ItemListener() {
+    /* Listens to the check boxes. */
+    public void itemStateChanged(ItemEvent e) {
+      int index = 0;
+      char c = '-';
+      Object source = e.getItemSelectable();
+      if (source == chinButton) {
+        index = 0;
+        c = 'c';
+      } else if (source == glassesButton) {
+        index = 1;
+        c = 'g';
+      } else if (source == hairButton) {
+        index = 2;
+        c = 'h';
+      } else if (source == teethButton) {
+        index = 3;
+        c = 't';
+      }
+      //Now that we know which button was pushed, find out
+      //whether it was selected or deselected.
+      if (e.getStateChange() == ItemEvent.DESELECTED) {
+        c = '-';
+      }
+      //Apply the change to the string.
+      choices.setCharAt(index, c);
+      updatePicture();
+    }
+  };
+  protected void updatePicture() {
+    //Get the icon corresponding to the image.
+    ImageIcon icon = new ImageIcon(
+                  "geek/geek-"
+                  + choices.toString()
+                  + ".gif");
+    pictureLabel.setIcon(icon);
+    pictureLabel.setToolTipText(choices.toString());
+    if (icon == null) {
+      pictureLabel.setText("Missing Image");
+    } else {
+      pictureLabel.setText(null);
+    }
+  }
+  /**
+   * 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.
+    JFrame frame = new JFrame("CheckBoxDemo");
+    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+    //Create and set up the content pane.
+    JComponent newContentPane = new CheckBoxDemo();
+    newContentPane.setOpaque(true); //content panes must be opaque
+    frame.setContentPane(newContentPane);
+    //Display the window.
+    frame.pack();
+    frame.setVisible(true);
+  }
+  public static void main(String[] args) {
+    //Schedule a job for the event-dispatching thread:
+    //creating and showing this application's GUI.
+    javax.swing.SwingUtilities.invokeLater(new Runnable() {
+      public void run() {
+        createAndShowGUI();
+      }
+    });
+  }
+}
+</code>
+Για να εκτελέσετε με επιτυχία το παραπάνω πρόγραμμα, θα χρειαστείτε επιπλέον τις φωτογραφίες που περιέχονται στο αρχείο zip {{:swing:geek-images.zip|}}.

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