JSpinner sending multiple events

[Chris Shepherd]

I have a series of JSpinners that I am using in a GUI. I also have an inline change listener for each of them to handle the input, check it for out-of-range and pass the new value along to my software. The problem is that every second or third click on the spinner's up and down arrows generates 2 calls to stateChanged(). This forces my code to run twice, and since it can be a time consuming process when it runs, I am essentially doubling my run time for this process. I thought I could be clever and just trap the second call that occurred less that 50ms from the first one. That worked great! .... Except I realized that the second call I trapped actually carries the new value and the first call getting through carried the old one.

So my question is this: Why am I having to jump through hoops to get data off my spinners? Why is it sometimes tossing an extra call before it sends the real one I am expecting?

Thanks for any help...
Chris

[Rob Spoor]

Movig to Swing

[Michael Dunn]

> So my question is this: Why am I having to jump through hoops to get data off my spinners? Why is it sometimes tossing an extra call before it sends the real one I am expecting?

the answer is in your custom code:
"I thought I could be clever and just trap the second call that occurred less that 50ms from the first one."


it works OK for me in this

    
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Testing
{
  public void buildGUI()
  {
    final JSpinner spinner = new JSpinner(new SpinnerNumberModel(50, 0, 100, 1));
    JFrame f = new JFrame();
    f.getContentPane().add(spinner);
    f.pack();
    f.setLocationRelativeTo(null);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
    final javax.swing.Timer timer = new javax.swing.Timer(250, new ActionListener(){
      public void actionPerformed(ActionEvent ae){
        System.out.println(spinner.getValue());
      }
    });
    timer.setRepeats(false);
    spinner.addChangeListener(new javax.swing.event.ChangeListener(){
      public void stateChanged(javax.swing.event.ChangeEvent ce){
        if(timer.isRunning() == false) timer.start();
        else timer.restart();
      }
    });
  }
  public static void main(String[] args)
  {
    SwingUtilities.invokeLater(new Runnable(){
      public void run(){
        new Testing().buildGUI();
      }
    });
  }
}

[Rob Spoor]

You could store the last spinner value, and only call your expensive code if the value has actually changed.

class MyChangeListener
{
    private Object lastValue = null;

    public void stateChanged(ChangeEvent ce)
    {
        Object newValue = spinner.getValue();
        if (lastValue == null || !lastValue.equals(newValue))
        {
            expensiveCode();
            lastValue = newValue;
        }
    }
}

You can make this a method local class if needed.

[Chris Shepherd]

Thanks Michael and Rob for your reply. I actually realized I could use Rob's solution after I posted this yesterday. I keep these values stored in some of my saved objects and so I just check against the last value I had stored and ignore it if it is the same. Michael, I actually thought about your solution first yesterday, but I was too bothered by the fact that the spinner generated inconsistent results to want to develop it into a solution. It took me enough time just to chase down why my results were not what I expected. Of course, seeing it in code looks fairly straight-forward and wouldn't have been that hard to do.

Thanks to both of you for your input. Still not sure why I'm sometimes getting two events, but I have a way around it now.

Chris