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    1   /*
    2    * Copyright (c) 1997, 2005, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package javax.swing;
   27   
   28   import java.awt.Component;
   29   
   30   
   31   /**
   32    * Identifies components that can be used as "rubber stamps" to paint
   33    * the cells in a JList.  For example, to use a JLabel as a
   34    * ListCellRenderer, you would write something like this:
   35    * <pre>
   36    * {@code
   37    * class MyCellRenderer extends JLabel implements ListCellRenderer<Object> {
   38    *     public MyCellRenderer() {
   39    *         setOpaque(true);
   40    *     }
   41    *
   42    *     public Component getListCellRendererComponent(JList<?> list,
   43    *                                                   Object value,
   44    *                                                   int index,
   45    *                                                   boolean isSelected,
   46    *                                                   boolean cellHasFocus) {
   47    *
   48    *         setText(value.toString());
   49    *
   50    *         Color background;
   51    *         Color foreground;
   52    *
   53    *         // check if this cell represents the current DnD drop location
   54    *         JList.DropLocation dropLocation = list.getDropLocation();
   55    *         if (dropLocation != null
   56    *                 && !dropLocation.isInsert()
   57    *                 && dropLocation.getIndex() == index) {
   58    *
   59    *             background = Color.BLUE;
   60    *             foreground = Color.WHITE;
   61    *
   62    *         // check if this cell is selected
   63    *         } else if (isSelected) {
   64    *             background = Color.RED;
   65    *             foreground = Color.WHITE;
   66    *
   67    *         // unselected, and not the DnD drop location
   68    *         } else {
   69    *             background = Color.WHITE;
   70    *             foreground = Color.BLACK;
   71    *         };
   72    *
   73    *         setBackground(background);
   74    *         setForeground(foreground);
   75    *
   76    *         return this;
   77    *     }
   78    * }
   79    * }
   80    * </pre>
   81    *
   82    * @param <E> the type of values this renderer can be used for
   83    *
   84    * @see JList
   85    * @see DefaultListCellRenderer
   86    *
   87    * @author Hans Muller
   88    */
   89   public interface ListCellRenderer<E>
   90   {
   91       /**
   92        * Return a component that has been configured to display the specified
   93        * value. That component's <code>paint</code> method is then called to
   94        * "render" the cell.  If it is necessary to compute the dimensions
   95        * of a list because the list cells do not have a fixed size, this method
   96        * is called to generate a component on which <code>getPreferredSize</code>
   97        * can be invoked.
   98        *
   99        * @param list The JList we're painting.
  100        * @param value The value returned by list.getModel().getElementAt(index).
  101        * @param index The cells index.
  102        * @param isSelected True if the specified cell was selected.
  103        * @param cellHasFocus True if the specified cell has the focus.
  104        * @return A component whose paint() method will render the specified value.
  105        *
  106        * @see JList
  107        * @see ListSelectionModel
  108        * @see ListModel
  109        */
  110       Component getListCellRendererComponent(
  111           JList<? extends E> list,
  112           E value,
  113           int index,
  114           boolean isSelected,
  115           boolean cellHasFocus);
  116   }

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