求解背景为什么不能改变?
import java.awt.BasicStroke;import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class sniper {
public JFrame mainjf;
public JPanel mainjp;
public static void main(String[] args) {
sniper sniper = new sniper();
}
public sniper(){
mainjf = new JFrame();
mainjp = new JPanel();
mainjf.setTitle("sniper");//设置标题
mainjf.setSize(800, 600);//设置大小
mainjf.setLayout(null);//设置布局
mainjf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//设置可关闭
mainjf.setVisible(true);//设置显隐
// mainjf.add(mainjp);
backgrood backgrood = new backgrood();
Container contentPane = mainjf.getContentPane();
contentPane.add("Center", backgrood);
// mainjp.paintComponents();
// mainjp.setBackground(Color.BLACK);
System.out.println("set jpanel background color is "+mainjp.getBackground());
System.out.println("set jframe background color is "+mainjf.getBackground());
System.out.println("sniper() run over");
}
}
class backgrood extends JPanel{
public void paintBorder(Graphics g) {
Graphics2D backgrood2d = (Graphics2D) g;
setBackground(Color.WHITE);
}
}
背景
补充:Java , Java相关