import  java.awt.*;
import  java.applet.*;
import  java.awt.event.*;
public class ScrollbarSlider extends Applet implements AdjustmentListener
{
      Scrollbar slider;
      TextField value;
      public void init()
      {
            setLayout(new BorderLayout()); //设置小应用程序的布局为BorderLayout。
            slider=new Scrollbar(Scrollbar.HORIZONTAL,100,1,0,200);
              //构造了一个水平的滚动杆。
            slider.setUnitIncrement(1);
            slider.setBlockIncrement(25);
            add("南",slider);
            value=new TextField("100",5);
            Panel p=new Panel();
            add("中心",p);
            p.add(value);
            slider.addAdjustmentListener(this);
     }
     public void adjustmentValueChanged(AdjustmentEvent e)
     {
           if(e.getAdjustable()==slider)
           {
                value.setText(new Integer(e.getValue()).toString());
           }
     }
}

上面滚动条程序运行后为什么会这样？


Microsoft Windows XP [版本 5.1.2600]
(C) 版权所有 1985-2001 Microsoft Corp.

C:\Documents and Settings\admin>cd c:\JavaTest2

C:\JavaTest2>appletviewer welcome.html
java.lang.IllegalArgumentException: cannot add to layout: unknown constraint: 南

        at java.awt.BorderLayout.addLayoutComponent(BorderLayout.java:463)
        at java.awt.BorderLayout.addLayoutComponent(BorderLayout.java:424)
        at java.awt.Container.addImpl(Container.java:1125)
        at java.awt.Container.add(Container.java:436)
        at ScrollbarSlider.init(ScrollbarSlider.java:15)
        at sun.applet.AppletPanel.run(AppletPanel.java:434)
        at java.lang.Thread.run(Thread.java:745)

C:\JavaTest2>

java.lang.IllegalArgumentException:
报错提示看看再改啊