程序如下，为什么窗口背景颜色显示不出来？还有什么是前景颜色？

Question

package 窗口;import java.awt.*;import javax.swing.*;public class Window2 extends JFrame{private Container cp;private JButton jb;public Window2(){setSize(300,200);setLocation(100,100);setLayout(null);setBackground(Color.lightGray  );setForeground(Color.orange );cp=this.getContentPane();init();}public void init(){jb=new JButton("单击我");jb.setBounds(100,80,200,40);jb.setForeground(Color.CYAN );jb.setFont(new Font("黑体",Font.BOLD ,20));cp.add(jb);}public static void main(String[] args){new Window2().setVisible(true);}}

Answer 1

前景颜色就是内容颜色