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Jlist action question

Posted on 2002-05-28
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Last Modified: 2012-06-27
I'm working on some code that uses jlist. It is working
fine except my action runs on mouse down and then again
on mouse up.  I just want one action for a single mouse
click (up and down).  Can anybody help?

Here is the code i'm using:

   listModel = new DefaultListModel();

    for (int i=0; i <= InData.size() -1; i++)
      listModel.addElement(InData.elementAt(i));

    list = new JList(listModel);
    list.setSelectionModeListSelectionModel.SINGLE_SELECTION);


list.addListSelectionListener(this);


  public void valueChanged(ListSelectionEvent e) {
       Object xx=list.getSelectedValue();
       jTextArea1.append(xx.toString()+ "\n");
  }
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Comment
Question by:afsac
  • 2
4 Comments
 
LVL 19

Accepted Solution

by:
Jim Cakalic earned 50 total points
ID: 7040529
Try:

    public void valueChanged(ListSelectionEvent e) {
        if (e.getValueIsAdjusting() == false) {
            Object xx=list.getSelectedValue();
            jTextArea1.append(xx.toString()+ "\n");
        }
    }

Best regards,
Jim Cakalic
0
 
LVL 92

Expert Comment

by:objects
ID: 7040627
Or use a MouseListener, and react to mouseClicked events.
0
 

Author Comment

by:afsac
ID: 7040692
Fantastic! Works like a charm.  I see from your code that
the solution is:

if (e.getValueIsAdjusting() == false) {
....
}

If you have time, could you give a brief explanation of
what this is, how in the world would I have ever found
this on my own, etc.

Thank you!

AFSAC
0
 
LVL 19

Expert Comment

by:Jim Cakalic
ID: 7042175
Straight out of the Java Tutorial section on using JList:
    http://java.sun.com/docs/books/tutorial/uiswing/components/list.html

No matter which selection mode your list uses, the list fires list selection events whenever the selection changes. You can process these events by adding a list selection listener to the list with the addListSelectionListener method. A list selection listener must implement one method: valueChanged. Here's the valueChanged method for the listener in SplitPaneDemo:

public void valueChanged(ListSelectionEvent e) {
    if (e.getValueIsAdjusting())
        return;

    JList theList = (JList)e.getSource();
    if (theList.isSelectionEmpty()) {
        picture.setIcon(null);
    } else {
        int index = theList.getSelectedIndex();
        ImageIcon newImage = new ImageIcon("images/" + (String)imageList.elementAt(index));
        picture.setIcon(newImage);
        picture.setPreferredSize(new Dimension(newImage.getIconWidth(), newImage.getIconHeight()));
        picture.revalidate();
    }
}

Many list selection events can be generated from a single user action such as a mouse click. The getValueIsAdjusting method returns true if the user is still manipulating the selection. This particular program is interested only in the final result of the user's action, so the valueChanged method updates the image only if getValueIsAdjusting returns false.

:-)
Jim
0

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