java - 为什么这个错误 Exception in thread "main"java.lang.IllegalArgumentException : adding a window to a container

Question

我正在尝试制作一个带有按钮的简单 GUI，但收到此错误。

import javax.swing.*;

public class GUIClass extends JFrame {

    public static void main (String[] args){
        // TODO Auto-generated method stub
        JFrame fm = new JFrame();
        JFrame btn = new JFrame("Click ME");
        btn.setBounds(50, 40, 120, 30);
        fm.add(btn);
        fm.setLayout(null);
        fm.setVisible(true);
        fm.setSize(400, 300);
    }
}

Answer 1

 JFrame btn = new JFrame("Click ME");

将其更改为；

JButton btn = new JButton("Click ME");

另外不要忘记导入 javax.swing.JButton;

另请检查一下: https://docs.oracle.com/javase/7/docs/api/javax/swing/JButton.html