这个关于JSlider的异常是什么意思？

[goosebeery]

我想用一个JSlider控制Timer的Delay,我是这样写的
slider.addChangeListener(
new ChangeListener() {
public void stateChanged( ChangeEvent changeEvent )
{
timer.setDelay(slider.getValue());
}
}
);
可是每次改变slider的值时出现了这样的异常
Exception occurred during event dispatching:
java.lang.NullPointerException
at ovt.gui.CurrentMjdToolbarComponents$8.stateChanged(CurrentMjdToolbarC
omponents.java:366)
at javax.swing.JSlider.fireStateChanged(Unknown Source)
at javax.swing.JSlider$ModelListener.stateChanged(Unknown Source)
at javax.swing.DefaultBoundedRangeModel.fireStateChanged(Unknown Source)

at javax.swing.DefaultBoundedRangeModel.setRangeProperties(Unknown Sourc
e)
at javax.swing.DefaultBoundedRangeModel.setValue(Unknown Source)
at javax.swing.JSlider.setValue(Unknown Source)
at javax.swing.plaf.basic.BasicSliderUI$TrackListener.mouseDragged(Unkno
wn Source)
at java.awt.AWTEventMulticaster.mouseDragged(Unknown Source)
at java.awt.Component.processMouseMotionEvent(Unknown Source)
at javax.swing.JComponent.processMouseMotionEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
why?请各位高手帮忙，谢谢！

[pxboy]

slider = new JSlider(1000, 10000);
slider.setValue(1000);
slider.setBounds(new Rectangle(137, 121, 206, 22));
slider.addChangeListener(new javax.swing.event.ChangeListener()
{
public void stateChanged(javax.swing.event.ChangeEvent changeEvent)
{
Timer timer = timerThread.getTimer();
if(timer != null)
timer.setDelay(slider.getValue());
}
});
jPanel.add(slider, null);



class TimerThread
implements Runnable
{
Timer timer;

public TimerThread()
{
}

public Timer getTimer()
{
return timer;
}

public void run()
{
ActionListener actionListener = new ActionListener()
{
public void actionPerformed(java.awt.event.ActionEvent e)
{
Date dateNow = new Date();
java.text.SimpleDateFormat fmt = null;
fmt = new java.text.SimpleDateFormat("[yyyy-MM-dd HH:mm:ss.SSS Z]");
String strFormat = fmt.format(dateNow);
System.out.println(strFormat);
}
};
timer = new Timer(1000,actionListener);
timer.start();
};
}

public void stop()
{
timer.stop();
}

}

[pxboy]

明明是个NullPointerException，看看你的timer是不是没有启动