🎊 java - JFrame：无法启动新窗口

我正在尝试学习 Java 和 JFrames。我把这个简单的应用程序放在了 Main 类启动 MainGui 类的地方。MainGui 将包含一堆按钮，每个按钮都有不同的功能（现在它只有 canadaFlagButton）。使用我创建的按钮打开 MainGui 的窗口没有问题。

但是，当我单击 canadaFlagButton 时，它应该会启动一个新窗口，但是却没有任何反应。

import javax.swing.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

public class MainGui extends JFrame implements ActionListener {

JButton canadaFlagButton;

MainGui() {

canadaFlagButton = new JButton("Canada Flag");

canadaFlagButton.setBounds(100, 100, 200, 50);

canadaFlagButton.setFocusable(false);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.setSize(400, 600);

this.setLayout(null);

this.add(canadaFlagButton);

this.setVisible(true);

}

@Override

public void actionPerformed(ActionEvent e) {

if(e.getSource()==canadaFlagButton) {

CanadaFlag window1 = new CanadaFlag();

}

}

}

//Can I draw the Canadian flag?

这是 CanadaFlag 类：

import javax.swing.*;

import java.awt.*;

public class CanadaFlag extends JFrame {

CanadaFlag() {

//creating label for maple leaf

JLabel leafLabel = new JLabel();

ImageIcon leaf = new ImageIcon("mapleleaf.png");

leafLabel.setIcon(leaf);

leafLabel.setVerticalAlignment(JLabel.CENTER);

leafLabel.setHorizontalAlignment(JLabel.CENTER);

JPanel redLeftPanel = new JPanel();

redLeftPanel.setBackground(Color.red);

redLeftPanel.setBounds(0, 0, 400, 1000);

JPanel redRightPanel = new JPanel();

redRightPanel.setBackground(Color.red);

redRightPanel.setBounds(1000, 0, 400, 1000);

JPanel whiteMiddlePanel = new JPanel();

whiteMiddlePanel.setBackground(Color.white);

whiteMiddlePanel.setBounds(400, 0, 600, 1000);

whiteMiddlePanel.setLayout(new BorderLayout());

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.setLayout(null);

this.setSize(1400, 1000);

this.setVisible(true);

this.add(redLeftPanel);

this.add(redRightPanel);

this.add(whiteMiddlePanel);

whiteMiddlePanel.add(leafLabel);

}

}