/* * 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.com/javaexamples2. */package com.davidflanagan.examples.gui;import java.awt.*;import java.awt.event.*;import javax.swing.*;import javax.swing.event.*;import javax.swing.border.*;import java.util.*;/** * 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);    }    /**     * This inner class is a simple demonstration of the ItemChooser component     * It uses command-line arguments as ItemChooser labels and values.     **/    public static class Demo {	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(" ");	    // 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.COMBOBOX);	    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();	}    }}