JSlider的一个问题

Question

当用鼠标将Applet的宽度变得很小时，异常就会发生呀，你可以再试试！！Exception occurred during event dispatching:
java.lang.NullPointerException
        at javax.swing.plaf.metal.MetalLookAndFeel.getControlDarkShadow(MetalLoo
kAndFeel.java:1076)
        at javax.swing.plaf.metal.MetalSliderUI.paintTrack(MetalSliderUI.java:15
8)
        at javax.swing.plaf.basic.BasicSliderUI.paint(BasicSliderUI.java:723)
        at javax.swing.plaf.ComponentUI.update(ComponentUI.java:39)
        at javax.swing.JComponent.paintComponent(JComponent.java:395)
        at javax.swing.JComponent.paint(JComponent.java:687)
        at javax.swing.JComponent.paintWithBuffer(JComponent.java:3878)
        at javax.swing.JComponent._paintImmediately(JComponent.java:3821)
        at javax.swing.JComponent.paintImmediately(JComponent.java:3672)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:370)        at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(System
EventQueueUtilities.java:124)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:154)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:337)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:131)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:98)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:85)

Answer 1

奇怪，当applet的宽度窄的不能再窄时，总是出现异常呀。怎么大家都没有发现？

Answer 2

这样试试(我想主要原因是CardLayout)：
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;public class Slider extends JApplet
{
    //P_c pc;
JPanel pa_main;
JSlider jslider;
public void init()
{
         Container contentPane=getContentPane();
         pa_main=new JPanel();         
jslider=new JSlider(50,100);
     jslider.setMajorTickSpacing(10);
     jslider.setMinimum(50);
     jslider.setMinorTickSpacing(10);
     jslider.setPaintLabels(true);
     jslider.setPaintTicks(true);
        pa_main.add(jslider,BorderLayout.CENTER);
      
         contentPane.add("Center",pa_main);    }}