tim/prune/save/UpDownToggler.java

   1 package tim.prune.save;
   2
   3 import javax.swing.JButton;
   4 import javax.swing.ListSelectionModel;
   5 import javax.swing.event.ListSelectionEvent;
   6 import javax.swing.event.ListSelectionListener;
   7
   8
   9 /**
  10  * Class to enable and disable a pair of up and down buttons
  11  */
  12 public class UpDownToggler implements ListSelectionListener
  13 {
  14         private JButton _upButton = null;
  15         private JButton _downButton = null;
  16         private int _maxIndex = 0;
  17
  18         /**
  19          * Constructor giving buttons and size
  20          * @param inUpButton up button
  21          * @param inDownButton down button
  22          * @param inListSize size of list
  23          */
  24         public UpDownToggler(JButton inUpButton, JButton inDownButton, int inListSize)
  25         {
  26                 _upButton = inUpButton;
  27                 _downButton = inDownButton;
  28                 _maxIndex = inListSize - 1;
  29         }
  30
  31
  32         /**
  33          * list selection has changed
  34          */
  35         public void valueChanged(ListSelectionEvent e)
  36         {
  37                 ListSelectionModel lsm = (ListSelectionModel) e.getSource();
  38                 if (lsm.isSelectionEmpty())
  39                 {
  40                         // no rows are selected
  41                         _upButton.setEnabled(false);
  42                         _downButton.setEnabled(false);
  43                 }
  44                 else
  45                 {
  46                         // single row is selected
  47                         int row = lsm.getMinSelectionIndex();
  48                         _upButton.setEnabled(row > 0);
  49                         _downButton.setEnabled(row >= 0 && row < _maxIndex);
  50                 }
  51         }
  52 }