Java/Swing Components/Item Chooser

ItemChooser

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.ru/javaexamples2.
 */
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;
import java.util.Iterator;
import javax.swing.BoxLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.border.EtchedBorder;
import javax.swing.border.TitledBorder;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
/**
 * This class is a Swing component that presents a choice to the user. It allows
 * the choice to be presented in a JList, in a JComboBox, or with a bordered
 * group of JRadioButton components. Additionally, it displays the name of the
 * choice with a JLabel. It allows an arbitrary value to be associated with each
 * possible choice. Note that this component only allows one item to be selected
 * at a time. Multiple selections are not supported.
 */
public class ItemChooser extends JPanel {
  // These fields hold property values for this component
  String name; // The overall name of the choice
  String[] labels; // The text for each choice option
  Object[] values; // Arbitrary values associated with each option
  int selection; // The selected choice
  int presentation; // How the choice is presented
  // These are the legal values for the presentation field
  public static final int LIST = 1;
  public static final int COMBOBOX = 2;
  public static final int RADIOBUTTONS = 3;
  // These components are used for each of the 3 possible presentations
  JList list; // One type of presentation
  JComboBox combobox; // Another type of presentation
  JRadioButton[] radiobuttons; // Yet another type
  // The list of objects that are interested in our state
  ArrayList listeners = new ArrayList();
  // The constructor method sets everything up
  public ItemChooser(String name, String[] labels, Object[] values,
      int defaultSelection, int presentation) {
    // Copy the constructor arguments to instance fields
    this.name = name;
    this.labels = labels;
    this.values = values;
    this.selection = defaultSelection;
    this.presentation = presentation;
    // If no values were supplied, use the labels
    if (values == null)
      this.values = labels;
    // Now create content and event handlers based on presentation type
    switch (presentation) {
    case LIST:
      initList();
      break;
    case COMBOBOX:
      initComboBox();
      break;
    case RADIOBUTTONS:
      initRadioButtons();
      break;
    }
  }
  // Initialization for JList presentation
  void initList() {
    list = new JList(labels); // Create the list
    list.setSelectedIndex(selection); // Set initial state
    // Handle state changes
    list.addListSelectionListener(new ListSelectionListener() {
      public void valueChanged(ListSelectionEvent e) {
        ItemChooser.this.select(list.getSelectedIndex());
      }
    });
    // Lay out list and name label vertically
    this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS)); // vertical
    this.add(new JLabel(name)); // Display choice name
    this.add(new JScrollPane(list)); // Add the JList
  }
  // Initialization for JComboBox presentation
  void initComboBox() {
    combobox = new JComboBox(labels); // Create the combo box
//    combobox.setSelectedIndex(selection); // Set initial state
    // Handle changes to the state
    combobox.addItemListener(new ItemListener() {
      public void itemStateChanged(ItemEvent e) {
        ItemChooser.this.select(combobox.getSelectedIndex());
      }
    });
    // Lay out combo box and name label horizontally
    this.setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
    this.add(new JLabel(name));
    this.add(combobox);
  }
  // Initialization for JRadioButton presentation
  void initRadioButtons() {
    // Create an array of mutually exclusive radio buttons
    radiobuttons = new JRadioButton[labels.length]; // the array
    ButtonGroup radioButtonGroup = new ButtonGroup(); // used for exclusion
    ChangeListener listener = new ChangeListener() { // A shared listener
      public void stateChanged(ChangeEvent e) {
        JRadioButton b = (JRadioButton) e.getSource();
        if (b.isSelected()) {
          // If we received this event because a button was
          // selected, then loop through the list of buttons to
          // figure out the index of the selected one.
          for (int i = 0; i < radiobuttons.length; i++) {
            if (radiobuttons[i] == b) {
              ItemChooser.this.select(i);
              return;
            }
          }
        }
      }
    };
    // Display the choice name in a border around the buttons
    this.setBorder(new TitledBorder(new EtchedBorder(), name));
    this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
    // Create the buttons, add them to the button group, and specify
    // the event listener for each one.
    for (int i = 0; i < labels.length; i++) {
      radiobuttons[i] = new JRadioButton(labels[i]);
      if (i == selection)
        radiobuttons[i].setSelected(true);
      radiobuttons[i].addChangeListener(listener);
      radioButtonGroup.add(radiobuttons[i]);
      this.add(radiobuttons[i]);
    }
  }
  // These simple property accessor methods just return field values
  // These are read-only properties. The values are set by the constructor
  // and may not be changed.
  public String getName() {
    return name;
  }
  public int getPresentation() {
    return presentation;
  }
  public String[] getLabels() {
    return labels;
  }
  public Object[] getValues() {
    return values;
  }
  /** Return the index of the selected item */
  public int getSelectedIndex() {
    return selection;
  }
  /** Return the object associated with the selected item */
  public Object getSelectedValue() {
    return values[selection];
  }
  /**
   * Set the selected item by specifying its index. Calling this method
   * changes the on-screen display but does not generate events.
   */
  public void setSelectedIndex(int selection) {
    switch (presentation) {
    case LIST:
      list.setSelectedIndex(selection);
      break;
    case COMBOBOX:
      combobox.setSelectedIndex(selection);
      break;
    case RADIOBUTTONS:
      radiobuttons[selection].setSelected(true);
      break;
    }
    this.selection = selection;
  }
  /**
   * This internal method is called when the selection changes. It stores the
   * new selected index, and fires events to any registered listeners. The
   * event listeners registered on the JList, JComboBox, or JRadioButtons all
   * call this method.
   */
  protected void select(int selection) {
    this.selection = selection; // Store the new selected index
    if (!listeners.isEmpty()) { // If there are any listeners registered
      // Create an event object to describe the selection
      ItemChooser.Event e = new ItemChooser.Event(this, selection,
          values[selection]);
      // Loop through the listeners using an Iterator
      for (Iterator i = listeners.iterator(); i.hasNext();) {
        ItemChooser.Listener l = (ItemChooser.Listener) i.next();
        l.itemChosen(e); // Notify each listener of the selection
      }
    }
  }
  // These methods are for event listener registration and deregistration
  public void addItemChooserListener(ItemChooser.Listener l) {
    listeners.add(l);
  }
  public void removeItemChooserListener(ItemChooser.Listener l) {
    listeners.remove(l);
  }
  /**
   * This inner class defines the event type generated by ItemChooser objects
   * The inner class name is Event, so the full name is ItemChooser.Event
   */
  public static class Event extends java.util.EventObject {
    int selectedIndex; // index of the selected item
    Object selectedValue; // the value associated with it
    public Event(ItemChooser source, int selectedIndex, Object selectedValue) {
      super(source);
      this.selectedIndex = selectedIndex;
      this.selectedValue = selectedValue;
    }
    public ItemChooser getItemChooser() {
      return (ItemChooser) getSource();
    }
    public int getSelectedIndex() {
      return selectedIndex;
    }
    public Object getSelectedValue() {
      return selectedValue;
    }
  }
  /**
   * This inner interface must be implemented by any object that wants to be
   * notified when the current selection in a ItemChooser component changes.
   */
  public interface Listener extends java.util.EventListener {
    public void itemChosen(ItemChooser.Event e);
  }
  public static void main(String[] args) {
    // Create a window, arrange to handle close requests
    final JFrame frame = new JFrame("ItemChooser Demo");
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    // A "message line" to display results in
    final JLabel msgline = new JLabel(" ");
    args = new String[]{"a","b","c"};
    // Create a panel holding three ItemChooser components
    JPanel chooserPanel = new JPanel();
    final ItemChooser c1 = new ItemChooser("Choice #1", args, null, 0,
        ItemChooser.LIST);
    final ItemChooser c2 = new ItemChooser("Choice #2", args, null, 0,
        ItemChooser.ruBOBOX);
    final ItemChooser c3 = new ItemChooser("Choice #3", args, null, 0,
        ItemChooser.RADIOBUTTONS);
    // An event listener that displays changes on the message line
    ItemChooser.Listener l = new ItemChooser.Listener() {
      public void itemChosen(ItemChooser.Event e) {
        msgline.setText(e.getItemChooser().getName() + ": "
            + e.getSelectedIndex() + ": " + e.getSelectedValue());
      }
    };
    c1.addItemChooserListener(l);
    c2.addItemChooserListener(l);
    c3.addItemChooserListener(l);
    // Instead of tracking every change with a ItemChooser.Listener,
    // applications can also just query the current state when
    // they need it. Here"s a button that does that.
    JButton report = new JButton("Report");
    report.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        // Note the use of multi-line italic HTML text
        // with the JOptionPane message dialog box.
        String msg = "<html><i>" + c1.getName() + ": "
            + c1.getSelectedValue() + "<br>" + c2.getName() + ": "
            + c2.getSelectedValue() + "<br>" + c3.getName() + ": "
            + c3.getSelectedValue() + "</i>";
        JOptionPane.showMessageDialog(frame, msg);
      }
    });
    // Add the 3 ItemChooser objects, and the Button to the panel
    chooserPanel.add(c1);
    chooserPanel.add(c2);
    chooserPanel.add(c3);
    chooserPanel.add(report);
    // Add the panel and the message line to the window
    Container contentPane = frame.getContentPane();
    contentPane.add(chooserPanel, BorderLayout.CENTER);
    contentPane.add(msgline, BorderLayout.SOUTH);
    // Set the window size and pop it up.
    frame.pack();
    frame.show();
  }
}