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swing:jradiobutton

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swing:jradiobutton [2020/03/30 07:48]
 swing:jradiobutton [2020/03/30 08:41]
gthanos
Line 1: Line 1:
 +===== Οι κλάσεις ButtonGroup και JRadioButton =====
 +
 +Τα //radio buttons// οργανώνονται σε //button groups//. Τα //radio buttons// είναι ανάλογα με τα //check boxes// με την ιδιαιτερότητα ότι μόνο ένα //radio button// μπορεί να είναι επιλεγμένο κάθε φορά στο ίδιο //button group//.  Επιπλέον, από τα κουμπιά ενός //button group// μόνο ένα είναι επιλέξιμο. 
 +
 +Κάθε φορά που ο χρήστης επιλέγει ένα radio button τότε δημιουργείται ένα αντικείμενο τύπου [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/ActionEvent.html|java.awt.events.ActionEvent]] το οποίο λαμβάνεται από ένα αντικείμενο τύπου [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/ActionListener.html|ActionListener]] που συνδέεται με το //radio button//. 
 +
 +Παράλληλα, δημιουργούνται και δύο αντικείμενα τύπου [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/ItemEvent.html|java.awt.events.ItemEvent]] ένα αντικείμενο για το button που επιλέχθηκε και ένα αντικείμενο για το button που απο-επιλέχθηκε (εάν υπήρξε τέτοιο), τα οποία λαμβάνονται από ένα αντικείμενο του τύπου [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/ItemListener.html|ItemListener]]. 
 +
 +Παρακάτω δίνονται δύο παραλλαγές του ιδίου προγράμματος **α)** με χρήση [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/ActionListener.html|ActionListener]] και **β)** με χρήση [[http://docs.oracle.com/javase/7/docs/api/java/awt/event/ItemListener.html|ItemListener]]. Για τα δύο παραδείγματα που ακολουθούν θα χρειαστείτε τις εικόνες {{:swing:animals.zip|}}.
 +
 +==== Παράδειγμα χρήσης ActionListener ====
 +
 +<code java RadioButtonDemo.java>
 +import java.awt.*;
 +import java.awt.event.*;
 +import javax.swing.*;
 +
 +/*
 + * RadioButtonDemo.java requires these files:
 + *   images/Bird.gif
 + *   images/Cat.gif
 + *   images/Dog.gif
 + *   images/Rabbit.gif
 + *   images/Pig.gif
 + */
 +public class RadioButtonDemo extends JPanel {
 +  static String birdString = "Bird";
 +  static String catString = "Cat";
 +  static String dogString = "Dog";
 +  static String rabbitString = "Rabbit";
 +  static String pigString = "Pig";
 +
 +  JLabel picture;
 +
 +  public RadioButtonDemo() {
 +    super(new BorderLayout());
 +
 +    //Create the radio buttons.
 +    JRadioButton birdButton = new JRadioButton(birdString);
 +    birdButton.setMnemonic(KeyEvent.VK_B);
 +    birdButton.setActionCommand(birdString);
 +    birdButton.setSelected(true);
 +
 +    JRadioButton catButton = new JRadioButton(catString);
 +    catButton.setMnemonic(KeyEvent.VK_C);
 +    catButton.setActionCommand(catString);
 +
 +    JRadioButton dogButton = new JRadioButton(dogString);
 +    dogButton.setMnemonic(KeyEvent.VK_D);
 +    dogButton.setActionCommand(dogString);
 +
 +    JRadioButton rabbitButton = new JRadioButton(rabbitString);
 +    rabbitButton.setMnemonic(KeyEvent.VK_R);
 +    rabbitButton.setActionCommand(rabbitString);
 +
 +    JRadioButton pigButton = new JRadioButton(pigString);
 +    pigButton.setMnemonic(KeyEvent.VK_P);
 +    pigButton.setActionCommand(pigString);
 +
 +    //Group the radio buttons.
 +    ButtonGroup group = new ButtonGroup();
 +    group.add(birdButton);
 +    group.add(catButton);
 +    group.add(dogButton);
 +    group.add(rabbitButton);
 +    group.add(pigButton);
 +
 +    //Register a listener for the radio buttons.
 +    birdButton.addActionListener(listener);
 +    catButton.addActionListener(listener);
 +    dogButton.addActionListener(listener);
 +    rabbitButton.addActionListener(listener);
 +    pigButton.addActionListener(listener);
 +
 +    //Set up the picture label.
 +    picture = new JLabel(new ImageIcon(
 +                       birdString
 +                       + ".gif"));
 +
 +    //The preferred size is hard-coded to be the width of the
 +    //widest image and the height of the tallest image.
 +    //A real program would compute this.
 +    picture.setPreferredSize(new Dimension(177, 122));
 +
 +
 +    //Put the radio buttons in a column in a panel.
 +    JPanel radioPanel = new JPanel(new GridLayout(0, 1));
 +    radioPanel.add(birdButton);
 +    radioPanel.add(catButton);
 +    radioPanel.add(dogButton);
 +    radioPanel.add(rabbitButton);
 +    radioPanel.add(pigButton);
 +
 +    add(radioPanel, BorderLayout.LINE_START);
 +    add(picture, BorderLayout.CENTER);
 +    setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
 +  }
 +
 +  ActionListener listener = new ActionListener() {
 +    /* Listens to the radio buttons. */
 +    public void actionPerformed(ActionEvent e) {
 +      picture.setIcon(new ImageIcon(e.getActionCommand() + ".gif"));
 +    }
 +  };
 +
 +  /**
 +   * 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("RadioButtonDemo");
 +    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 +
 +    //Create and set up the content pane.
 +    JComponent newContentPane = new RadioButtonDemo();
 +    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>
 +
 +==== Παράδειγμα χρήσης ItemListener ====
 +
 +<code java RadioButtonDemo2.java>
 +import java.awt.*;
 +import java.awt.event.*;
 +import javax.swing.*;
 +
 +/*
 + * RadioButtonDemo.java requires these files:
 + *   images/Bird.gif
 + *   images/Cat.gif
 + *   images/Dog.gif
 + *   images/Rabbit.gif
 + *   images/Pig.gif
 + */
 +public class RadioButtonDemo2 extends JPanel {
 +  
 +  static String birdString = "Bird";
 +  static String catString = "Cat";
 +  static String dogString = "Dog";
 +  static String rabbitString = "Rabbit";
 +  static String pigString = "Pig";
 +
 +  JLabel picture;
 +
 +  public RadioButtonDemo2() {
 +    super(new BorderLayout());
 +
 +    //Create the radio buttons.
 +    JRadioButton birdButton = new JRadioButton(birdString);
 +    birdButton.setMnemonic(KeyEvent.VK_B);
 +    birdButton.setSelected(true);
 +
 +    JRadioButton catButton = new JRadioButton(catString);
 +    catButton.setMnemonic(KeyEvent.VK_C);
 +
 +    JRadioButton dogButton = new JRadioButton(dogString);
 +    dogButton.setMnemonic(KeyEvent.VK_D);
 +
 +    JRadioButton rabbitButton = new JRadioButton(rabbitString);
 +    rabbitButton.setMnemonic(KeyEvent.VK_R);
 +
 +    JRadioButton pigButton = new JRadioButton(pigString);
 +    pigButton.setMnemonic(KeyEvent.VK_P);
 +
 +    //Group the radio buttons.
 +    ButtonGroup group = new ButtonGroup();
 +    group.add(birdButton);
 +    group.add(catButton);
 +    group.add(dogButton);
 +    group.add(rabbitButton);
 +    group.add(pigButton);
 +
 +    //Register a listener for the radio buttons.
 +    birdButton.addItemListener(itemListener);
 +    catButton.addItemListener(itemListener);
 +    dogButton.addItemListener(itemListener);
 +    rabbitButton.addItemListener(itemListener);
 +    pigButton.addItemListener(itemListener);
 +
 +    //Set up the picture label.
 +    picture = new JLabel(new ImageIcon(birdString + ".gif"));
 +
 +    //The preferred size is hard-coded to be the width of the
 +    //widest image and the height of the tallest image.
 +    //A real program would compute this.
 +    picture.setPreferredSize(new Dimension(177, 122));
 +
 +
 +    //Put the radio buttons in a column in a panel.
 +    JPanel radioPanel = new JPanel(new GridLayout(0, 1));
 +    radioPanel.add(birdButton);
 +    radioPanel.add(catButton);
 +    radioPanel.add(dogButton);
 +    radioPanel.add(rabbitButton);
 +    radioPanel.add(pigButton);
 +
 +    add(radioPanel, BorderLayout.LINE_START);
 +    add(picture, BorderLayout.CENTER);
 +    setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
 +  }
 +
 +  ItemListener itemListener = new ItemListener() {
 +    public void itemStateChanged(ItemEvent e) {
 +      if(e.getStateChange() == ItemEvent.SELECTED) {
 +        JRadioButton btn = (JRadioButton)e.getItemSelectable();
 +        picture.setIcon(new ImageIcon(btn.getText() + ".gif"));
 +      }
 +    }
 +  };
 +
 +  /**
 +   * 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("RadioButtonDemo");
 +    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 +
 +    //Create and set up the content pane.
 +    JComponent newContentPane = new RadioButtonDemo();
 +    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>
 +
 +
 +
  
swing/jradiobutton.txt · Last modified: 2020/03/30 07:48 (external edit)

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