comboboxcelleditor.java

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/**    
  * Copyright (C) 2006, Laboratorio di Valutazione delle Prestazioni - Politecnico di Milano

  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.

  * This program 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 for more details.

  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
  
package jmt.gui.common.editors;

import javax.swing.*;
import javax.swing.table.TableCellEditor;
import javax.swing.table.TableCellRenderer;
import java.awt.*;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.util.HashMap;

/**
 * <p>Title: ComboBox Table CellViewer/CellEditor</p>
 * <p>Description: A component to display a Combobox as both a viewer and an editor in a table.
 * Internally caches already allocated editors to avoid creation of too many ComboBoxes.
 * Renderer instance is a single element cached too.</p>
 *
 * @author Bertoli Marco
 *         Date: 9-gen-2006
 *         Time: 9.44.44
 */
public class ComboBoxCellEditor extends AbstractCellEditor implements TableCellEditor, CellEditor,
                                    TableCellRenderer {
    // Limit maximum cache... This is not really needed but it's good programming to avoid memory leakage
    protected static final int MAX_CACHESIZE = 128;
    // Uses to cache equivalent editors
    protected static HashMap editorCache;
    // Component used as editor
    protected JComboBox comboBox;
    // component used as a renderer
    protected static ComboBoxCellEditor renderer;

    /**
     * Returns a new instance of CellEditor that will display items in a ComboBox
     * @param items items to be selected from the ComboBox
     * @return CellEditor created or cached copy with the same items
     */
    public static ComboBoxCellEditor getEditorInstance(Object[] items) {
        ComboBoxCellEditor instance;
        if (editorCache == null)
            editorCache = new HashMap();
        // If items[] is new, creates a new comboBox, otherwise reuse old one
        if (!editorCache.containsKey(items)) {
            instance = new ComboBoxCellEditor(items);
            // Cleans cache when it is bigger than MAXCACHE
            if (editorCache.size() >= MAX_CACHESIZE)
                editorCache.clear();
            editorCache.put(items, instance);
        }
        else
            instance = (ComboBoxCellEditor) editorCache.get(items);
        return instance;
    }

    /**
     * Returns a new instance of CellRenderer that will display current item in a ComboBox
     * @return cached CellRenderer
     */
    public static ComboBoxCellEditor getRendererInstance() {
        if (renderer == null)
            renderer = new ComboBoxCellEditor();
        return renderer;
    }

    /**
     * Creates a new ComboBox editor or renderer basing on given array of items
     * @param items array of elements to be shown on the ComboBox
     */
    protected ComboBoxCellEditor(Object[] items) {
        comboBox = new JComboBox(items);
    }

    protected ComboBoxCellEditor() {
        comboBox = new JComboBox();
    }

    /**
     * Returns the value contained in the editor.
     *
     * @return the value contained in the editor
     */
    public Object getCellEditorValue() {
        return comboBox.getSelectedItem();
    }

    /**
     * Sets an initial <code>value</code> for the editor.  This will cause
     * the editor to <code>stopEditing</code> and lose any partially
     * edited value if the editor is editing when this method is called. <p>
     * <p/>
     * Returns the component that should be added to the client's
     * <code>Component</code> hierarchy.  Once installed in the client's
     * hierarchy this component will then be able to draw and receive
     * user input.
     *
     * @param    table        the <code>JTable</code> that is asking the
     * editor to edit; can be <code>null</code>
     * @param    value        the value of the cell to be edited; it is
     * up to the specific editor to interpret
     * and draw the value.  For example, if value is
     * the string "true", it could be rendered as a
     * string or it could be rendered as a check
     * box that is checked.  <code>null</code>
     * is a valid value
     * @param    isSelected    true if the cell is to be rendered with
     * highlighting
     * @param    row the row of the cell being edited
     * @param    column the column of the cell being edited
     * @return the component for editing
     */
    public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {
        comboBox.setSelectedItem(value);
        comboBox.addItemListener(new ItemListener() {

            /**
             * Invoked when an item has been selected or deselected by the user.
             * Makes the renderer to reappear after editing finishes
             */
            public void itemStateChanged(ItemEvent e) {
                //Make the renderer reappear.
                fireEditingStopped();
            }
        });
        return comboBox;
    }

    /**
     * Returns the component used for drawing the cell.  This method is
     * used to configure the renderer appropriately before drawing.
     *
     * @param    table        the <code>JTable</code> that is asking the
     * renderer to draw; can be <code>null</code>
     * @param    value        the value of the cell to be rendered.  It is
     * up to the specific renderer to interpret
     * and draw the value.  For example, if
     * <code>value</code>
     * is the string "true", it could be rendered as a
     * string or it could be rendered as a check
     * box that is checked.  <code>null</code> is a
     * valid value
     * @param    isSelected    true if the cell is to be rendered with the
     * selection highlighted; otherwise false
     * @param    hasFocus    if true, render cell appropriately.  For
     * example, put a special border on the cell, if
     * the cell can be edited, render in the color used
     * to indicate editing
     * @param    row     the row index of the cell being drawn.  When
     * drawing the header, the value of
     * <code>row</code> is -1
     * @param    column     the column index of the cell being drawn
     */
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
        // If cell is not editable, returns standard renderer
        if (!table.isCellEditable(row, column))
            return table.getDefaultRenderer(value.getClass())
                    .getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);

        comboBox.removeAllItems();
        if (value != null) {
            comboBox.addItem(value);
            comboBox.setSelectedItem(value);
        }
        if (!isSelected) {
            comboBox.setBackground(table.getBackground());
            comboBox.setForeground(table.getForeground());
        }
        else {
            comboBox.setBackground(table.getSelectionBackground());
            comboBox.setForeground(table.getSelectionForeground());
        }
        return comboBox;
    }
}