就是我的源程序(java applet)能顺利通过编译,可是在appletviewer里查看的时候却提示:“未初始化小程序”,用JCreator调试提示错误为: “ Initializing jdb ... > run sun.applet.AppletViewer Example12_2.htm > VM Started: java.lang.IllegalArgumentException: cannot add to layout: constraint must be a string at java.awt.CardLayout.addLayoutComponent(CardLayout.java:190) at java.awt.Container.addImpl(Container.java:482) at java.awt.Container.add(Container.java:298) at Example12_2.Example12_2.init(Example12_2.java:36) at sun.applet.AppletPanel.run(AppletPanel.java:341) at java.lang.Thread.run(Thread.java:536) ” 我的布局管理器的使用代码片段为:
mycard=new CardLayout();
//......
Panel p=new Panel();
p.setLayout(mycard);
//.....
p.add(mycanvas[i]);
//mycanvas 是我自定义Mycanvas画图类的对象
//最后用三个按钮驱动显示不同的层
public void actionPerformed(ActionEvent e)
{ if(e.getSource()==button1){ mycard.first(p); }
else if(e.getSource()==button2) {mycard.next(p);}
else if(e.getSource()==button3) {mycard.last(p);}
}