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