窗体添加按钮的问题
程序代码：import javax.swing.*;
import java.awt.*;
public class Window1 {
public static void main(String[] args) {
JFrame Win1=new JFrame("第一个窗体");
BorderLayout Layout=new BorderLayout();
Win1.getContentPane().setLayout(null);
Win1.setBounds(100,100,500,500);
Win1.getContentPane().setBackground(Color.white);//为什么要getContentPane()?
JButton Btn1=new JButton("Command1");
Btn1.setBounds(10,10,150,50);
Btn1.setVisible(true);
Btn1.setForeground(Color.red);
Win1.setVisible(true);
//Win1.getContentPane().add(Btn1); //为什么一定要这句才能添加一个按钮?
Win1.add(Btn1);
}运行出现以下错误:
java.lang.Error: Do not use javax.swing.JFrame.add() use javax.swing.JFrame.getContentPane().add() instead
at javax.swing.JFrame.createRootPaneException(Unknown Source)
at javax.swing.JFrame.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
改用Win1.getContentPane().add(Btn1); 才可以正常添加,为什么?
