/*

 * Copyright 1997-2008 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package javax.swing;

import java.beans.PropertyChangeEvent;

import java.beans.PropertyChangeListener;

import java.beans.Transient;

import java.util.*;

import java.awt.*;

import java.awt.event.*;

import java.io.Serializable;

import java.io.ObjectOutputStream;

import java.io.IOException;

import javax.swing.event.*;

import javax.swing.plaf.*;

import javax.accessibility.*;

/**

 * A component that combines a button or editable field and a drop-down list.

 * The user can select a value from the drop-down list, which appears at the

 * user's request. If you make the combo box editable, then the combo box

 * includes an editable field into which the user can type a value.

 * <p>

 * <strong>Warning:</strong> Swing is not thread safe. For more

 * information see <a

 * href="package-summary.html#threading">Swing's Threading

 * Policy</a>.

 * <p>

 * <strong>Warning:</strong>

 * Serialized objects of this class will not be compatible with

 * future Swing releases. The current serialization support is

 * appropriate for short term storage or RMI between applications running

 * the same version of Swing.  As of 1.4, support for long term storage

 * of all JavaBeans<sup><font size="-2">TM</font></sup>

 * has been added to the <code>java.beans</code> package.

 * Please see {@link java.beans.XMLEncoder}.

 *

 * <p>

 * See <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/combobox.html">How to Use Combo Boxes</a>

 * in <a href="http://java.sun.com/Series/Tutorial/index.html"><em>The Java Tutorial</em></a>

 * for further information.

 * <p>

 * @see ComboBoxModel

 * @see DefaultComboBoxModel

 *

 * @beaninfo

 *   attribute: isContainer false

 * description: A combination of a text field and a drop-down list.

 *

 * @author Arnaud Weber

 * @author Mark Davidson

 */

public class JComboBox extends JComponent

implements ItemSelectable,ListDataListener,ActionListener, Accessible {

    /**

     * @see #getUIClassID

     * @see #readObject

     */

    private static final String uiClassID = "ComboBoxUI";

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #getModel

     * @see #setModel

     */

    protected ComboBoxModel    dataModel;

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #getRenderer

     * @see #setRenderer

     */

    protected ListCellRenderer renderer;

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #getEditor

     * @see #setEditor

     */

    protected ComboBoxEditor       editor;

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #getMaximumRowCount

     * @see #setMaximumRowCount

     */

    protected int maximumRowCount = 8;

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #isEditable

     * @see #setEditable

     */

    protected boolean isEditable  = false;

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #setKeySelectionManager

     * @see #getKeySelectionManager

     */

    protected KeySelectionManager keySelectionManager = null;

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #setActionCommand

     * @see #getActionCommand

     */

    protected String actionCommand = "comboBoxChanged";

    /**

     * This protected field is implementation specific. Do not access directly

     * or override. Use the accessor methods instead.

     *

     * @see #setLightWeightPopupEnabled

     * @see #isLightWeightPopupEnabled

     */

    protected boolean lightWeightPopupEnabled = JPopupMenu.getDefaultLightWeightPopupEnabled();

    /**

     * This protected field is implementation specific. Do not access directly

     * or override.

     */

    protected Object selectedItemReminder = null;

    private Object prototypeDisplayValue;

    // Flag to ensure that infinite loops do not occur with ActionEvents.

    private boolean firingActionEvent = false;

    // Flag to ensure the we don't get multiple ActionEvents on item selection.

    private boolean selectingItem = false;

    /**

     * Creates a <code>JComboBox</code> that takes its items from an

     * existing <code>ComboBoxModel</code>.  Since the

     * <code>ComboBoxModel</code> is provided, a combo box created using

     * this constructor does not create a default combo box model and

     * may impact how the insert, remove and add methods behave.

     *

     * @param aModel the <code>ComboBoxModel</code> that provides the

     *          displayed list of items

     * @see DefaultComboBoxModel

     */

    public JComboBox(ComboBoxModel aModel) {

        super();

        setModel(aModel);

        init();

    }

    /**

     * Creates a <code>JComboBox</code> that contains the elements

     * in the specified array.  By default the first item in the array

     * (and therefore the data model) becomes selected.

     *

     * @param items  an array of objects to insert into the combo box

     * @see DefaultComboBoxModel

     */

    public JComboBox(final Object items[]) {

        super();

        setModel(new DefaultComboBoxModel(items));

        init();

    }

    /**

     * Creates a <code>JComboBox</code> that contains the elements

     * in the specified Vector.  By default the first item in the vector

     * (and therefore the data model) becomes selected.

     *

     * @param items  an array of vectors to insert into the combo box

     * @see DefaultComboBoxModel

     */

    public JComboBox(Vector<?> items) {

        super();

        setModel(new DefaultComboBoxModel(items));

        init();

    }

    /**

     * Creates a <code>JComboBox</code> with a default data model.

     * The default data model is an empty list of objects.

     * Use <code>addItem</code> to add items.  By default the first item

     * in the data model becomes selected.

     *

     * @see DefaultComboBoxModel

     */

    public JComboBox() {

        super();

        setModel(new DefaultComboBoxModel());

        init();

    }

    private void init() {

        installAncestorListener();

        updateUI();

    }

    protected void installAncestorListener() {

        addAncestorListener(new AncestorListener(){

                                public void ancestorAdded(AncestorEvent event){ hidePopup();}

                                public void ancestorRemoved(AncestorEvent event){ hidePopup();}

                                public void ancestorMoved(AncestorEvent event){

                                    if (event.getSource() != JComboBox.this)

                                        hidePopup();

                                }});

    }

    /**

     * Sets the L&F object that renders this component.

     *

     * @param ui  the <code>ComboBoxUI</code> L&F object

     * @see UIDefaults#getUI

     *

     * @beaninfo

     *        bound: true

     *       hidden: true

     *    attribute: visualUpdate true

     *  description: The UI object that implements the Component's LookAndFeel.

     */

    public void setUI(ComboBoxUI ui) {

        super.setUI(ui);

    }

    /**

     * Resets the UI property to a value from the current look and feel.

     *

     * @see JComponent#updateUI

     */

    public void updateUI() {

        setUI((ComboBoxUI)UIManager.getUI(this));

        ListCellRenderer renderer = getRenderer();

        if (renderer instanceof Component) {

            SwingUtilities.updateComponentTreeUI((Component)renderer);

        }

    }

    /**

     * Returns the name of the L&F class that renders this component.

     *

     * @return the string "ComboBoxUI"

     * @see JComponent#getUIClassID

     * @see UIDefaults#getUI

     */

    public String getUIClassID() {

        return uiClassID;

    }

    /**

     * Returns the L&F object that renders this component.

     *

     * @return the ComboBoxUI object that renders this component

     */

    public ComboBoxUI getUI() {

        return(ComboBoxUI)ui;

    }

    /**

     * Sets the data model that the <code>JComboBox</code> uses to obtain

     * the list of items.

     *

     * @param aModel the <code>ComboBoxModel</code> that provides the

     *  displayed list of items

     *

     * @beaninfo

     *        bound: true

     *  description: Model that the combo box uses to get data to display.

     */

    public void setModel(ComboBoxModel aModel) {

        ComboBoxModel oldModel = dataModel;

        if (oldModel != null) {

            oldModel.removeListDataListener(this);

        }

        dataModel = aModel;

        dataModel.addListDataListener(this);

        // set the current selected item.

        selectedItemReminder = dataModel.getSelectedItem();

        firePropertyChange( "model", oldModel, dataModel);

    }

    /**

     * Returns the data model currently used by the <code>JComboBox</code>.

     *

     * @return the <code>ComboBoxModel</code> that provides the displayed

     *                  list of items

     */

    public ComboBoxModel getModel() {

        return dataModel;

    }

    /*

     * Properties

     */

    /**

     * Sets the <code>lightWeightPopupEnabled</code> property, which

     * provides a hint as to whether or not a lightweight

     * <code>Component</code> should be used to contain the

     * <code>JComboBox</code>, versus a heavyweight

     * <code>Component</code> such as a <code>Panel</code>

     * or a <code>Window</code>.  The decision of lightweight

     * versus heavyweight is ultimately up to the

     * <code>JComboBox</code>.  Lightweight windows are more

     * efficient than heavyweight windows, but lightweight

     * and heavyweight components do not mix well in a GUI.

     * If your application mixes lightweight and heavyweight

     * components, you should disable lightweight popups.

     * The default value for the <code>lightWeightPopupEnabled</code>

     * property is <code>true</code>, unless otherwise specified

     * by the look and feel.  Some look and feels always use

     * heavyweight popups, no matter what the value of this property.

     * <p>

     * See the article <a href="http://java.sun.com/products/jfc/tsc/articles/mixing/index.html">Mixing Heavy and Light Components</a>

     * on <a href="http://java.sun.com/products/jfc/tsc">

     * <em>The Swing Connection</em></a>

     * This method fires a property changed event.

     *

     * @param aFlag if <code>true</code>, lightweight popups are desired

     *

     * @beaninfo

     *        bound: true

     *       expert: true

     *  description: Set to <code>false</code> to require heavyweight popups.

     */

    public void setLightWeightPopupEnabled(boolean aFlag) {

        boolean oldFlag = lightWeightPopupEnabled;

        lightWeightPopupEnabled = aFlag;

        firePropertyChange("lightWeightPopupEnabled", oldFlag, lightWeightPopupEnabled);

    }

    /**

     * Gets the value of the <code>lightWeightPopupEnabled</code>

     * property.

     *

     * @return the value of the <code>lightWeightPopupEnabled</code>

     *    property

     * @see #setLightWeightPopupEnabled

     */

    public boolean isLightWeightPopupEnabled() {

        return lightWeightPopupEnabled;

    }

    /**

     * Determines whether the <code>JComboBox</code> field is editable.

     * An editable <code>JComboBox</code> allows the user to type into the

     * field or selected an item from the list to initialize the field,

     * after which it can be edited. (The editing affects only the field,

     * the list item remains intact.) A non editable <code>JComboBox</code>

     * displays the selected item in the field,

     * but the selection cannot be modified.

     *

     * @param aFlag a boolean value, where true indicates that the

     *                  field is editable

     *

     * @beaninfo

     *        bound: true

     *    preferred: true

     *  description: If true, the user can type a new value in the combo box.

     */

    public void setEditable(boolean aFlag) {

        boolean oldFlag = isEditable;

        isEditable = aFlag;

        firePropertyChange( "editable", oldFlag, isEditable );

    }

    /**

     * Returns true if the <code>JComboBox</code> is editable.

     * By default, a combo box is not editable.

     *

     * @return true if the <code>JComboBox</code> is editable, else false

     */

    public boolean isEditable() {

        return isEditable;

    }

    /**

     * Sets the maximum number of rows the <code>JComboBox</code> displays.

     * If the number of objects in the model is greater than count,

     * the combo box uses a scrollbar.

     *

     * @param count an integer specifying the maximum number of items to

     *              display in the list before using a scrollbar

     * @beaninfo

     *        bound: true

     *    preferred: true

     *  description: The maximum number of rows the popup should have

     */

    public void setMaximumRowCount(int count) {

        int oldCount = maximumRowCount;

        maximumRowCount = count;

        firePropertyChange( "maximumRowCount", oldCount, maximumRowCount );

    }

    /**

     * Returns the maximum number of items the combo box can display

     * without a scrollbar

     *

     * @return an integer specifying the maximum number of items that are

     *         displayed in the list before using a scrollbar

     */

    public int getMaximumRowCount() {

        return maximumRowCount;

    }

    /**

     * Sets the renderer that paints the list items and the item selected from the list in

     * the JComboBox field. The renderer is used if the JComboBox is not

     * editable. If it is editable, the editor is used to render and edit

     * the selected item.

     * <p>

     * The default renderer displays a string or an icon.

     * Other renderers can handle graphic images and composite items.

     * <p>

     * To display the selected item,

     * <code>aRenderer.getListCellRendererComponent</code>

     * is called, passing the list object and an index of -1.

     *

     * @param aRenderer  the <code>ListCellRenderer</code> that

     *                  displays the selected item

     * @see #setEditor

     * @beaninfo

     *      bound: true

     *     expert: true

     *  description: The renderer that paints the item selected in the list.

     */

    public void setRenderer(ListCellRenderer aRenderer) {

        ListCellRenderer oldRenderer = renderer;

        renderer = aRenderer;

        firePropertyChange( "renderer", oldRenderer, renderer );

        invalidate();

    }

    /**

     * Returns the renderer used to display the selected item in the

     * <code>JComboBox</code> field.

     *

     * @return  the <code>ListCellRenderer</code> that displays

     *                  the selected item.

     */

    public ListCellRenderer getRenderer() {

        return renderer;

    }

    /**

     * Sets the editor used to paint and edit the selected item in the

     * <code>JComboBox</code> field.  The editor is used only if the

     * receiving <code>JComboBox</code> is editable. If not editable,

     * the combo box uses the renderer to paint the selected item.

     *

     * @param anEditor  the <code>ComboBoxEditor</code> that

     *                  displays the selected item

     * @see #setRenderer

     * @beaninfo

     *     bound: true

     *    expert: true

     *  description: The editor that combo box uses to edit the current value

     */

    public void setEditor(ComboBoxEditor anEditor) {

        ComboBoxEditor oldEditor = editor;

        if ( editor != null ) {

            editor.removeActionListener(this);

        }

        editor = anEditor;

        if ( editor != null ) {

            editor.addActionListener(this);

        }

        firePropertyChange( "editor", oldEditor, editor );

    }

    /**

     * Returns the editor used to paint and edit the selected item in the

     * <code>JComboBox</code> field.

     *

     * @return the <code>ComboBoxEditor</code> that displays the selected item

     */

    public ComboBoxEditor getEditor() {

        return editor;

    }

    //

    // Selection

    //

    /**

     * Sets the selected item in the combo box display area to the object in

     * the argument.

     * If <code>anObject</code> is in the list, the display area shows

     * <code>anObject</code> selected.

     * <p>