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swing:jcheckbox

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swing:jcheckbox [2020/03/30 07:29]
 swing:jcheckbox [2020/03/30 08:29]
gthanos
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 +===== 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 {
 +              
 +  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|}}.
  
swing/jcheckbox.txt · Last modified: 2020/03/30 07:29 (external edit)

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