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 = 2;
  17
  18         /**
  19          * Constructor giving buttons to enable/disable
  20          * @param inUpButton up button
  21          * @param inDownButton down button
  22          */
  23         public UpDownToggler(JButton inUpButton, JButton inDownButton)
  24         {
  25                 _upButton = inUpButton;
  26                 _downButton = inDownButton;
  27         }
  28
  29         /**
  30          * Set the list size
  31          * @param inListSize number of items in list
  32          */
  33         public void setListSize(int inListSize)
  34         {
  35                 _maxIndex = inListSize - 1;
  36         }
  37
  38         /**
  39          * list selection has changed
  40          */
  41         public void valueChanged(ListSelectionEvent e)
  42         {
  43                 ListSelectionModel lsm = (ListSelectionModel) e.getSource();
  44                 if (lsm.isSelectionEmpty())
  45                 {
  46                         // no rows are selected
  47                         _upButton.setEnabled(false);
  48                         _downButton.setEnabled(false);
  49                 }
  50                 else
  51                 {
  52                         // single row is selected
  53                         int row = lsm.getMinSelectionIndex();
  54                         _upButton.setEnabled(row > 0);
  55                         _downButton.setEnabled(row >= 0 && row < _maxIndex);
  56                 }
  57         }
  58 }