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--- swing:jcheckbox [2018/03/23 11:29]
gthanos created
+++ swing:jcheckbox [2020/03/30 07:29]
@@ 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(this);
-    glassesButton.addItemListener(this);
-    hairButton.addItemListener(this);
-    teethButton.addItemListener(this);
-    //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 checkPanel = new JPanel(new GridLayout(0, 1));
-    checkPanel.add(chinButton);
-    checkPanel.add(glassesButton);
-    checkPanel.add(hairButton);
-    checkPanel.add(teethButton);
-    add(checkPanel, BorderLayout.LINE_START);
-    add(pictureLabel, BorderLayout.CENTER);
-    setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
-  }
-  /** 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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