单击JFrame上的退出按钮需要关闭JFrame
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【中文标题】单击JFrame上的退出按钮需要关闭JFrame【英文标题】：Need to close JFrame on clicking Exit button on JFrame 【发布时间】：2022-01-18 18:28:28 【问题描述】：我正在创建一个简单的 Java 应用程序，而且我是 Java 新手。请帮我解决这个问题
我正在使用 java 8，我试图从一个帧移动到另一个帧，我可以这样做，但为此，我在代码中出现了一些异常，我无法弄清楚为什么以及那是什么
下面是我的代码，错误发生在下面。
package oops;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class HumanBenchmarkApp implements ActionListener
JFrame AppWindow, ReflexFrame, VisualFrame, CreditsFrame;
JLabel Title;
JButton Game1, Game2, Credits, Exit;
public HumanBenchmarkApp()
AppWindow = new JFrame("Human Benchmark");
AppWindow.setSize(400, 400);
JPanel Content = new JPanel();
Content.setBorder(new EmptyBorder(10, 10, 10, 10));
Content.setLayout(new GridBagLayout());
try
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
catch(Exception e)
System.err.println(e.getMessage());
AppWindow.setLayout(new BoxLayout(AppWindow.getContentPane(),BoxLayout.Y_AXIS));
Title = new JLabel("<html><h1><strong>Human Benchmark App</strong></h1><br></html>");
Game1 = new JButton("<html><h4>Reflex Action Test</h4></html>");
Game2 = new JButton("<html><h4>Visual Memory Test</h4></html>");
Credits = new JButton("<html><h4>Credits</h4></html>");
Exit = new JButton("<html><h4>Exit</h4></html>");
Game1.addActionListener(this);
Game2.addActionListener(this);
Credits.addActionListener(this);
Exit.addActionListener(this);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.anchor = GridBagConstraints.NORTH;
Content.add(Title, gbc);
gbc.anchor = GridBagConstraints.CENTER;
gbc.fill = GridBagConstraints.HORIZONTAL;
JPanel Buttons = new JPanel(new GridBagLayout());
Buttons.add(Game1, gbc);
Buttons.add(Game2, gbc);
Buttons.add(Credits, gbc);
Buttons.add(Exit, gbc);
gbc.weighty = 1;
Content.add(Buttons);
AppWindow.add(Content);
AppWindow.setVisible(true);
AppWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
public static void main(String[] args)
new HumanBenchmarkApp();
@Override
public void actionPerformed(ActionEvent e)
JButton clicked = (JButton)e.getSource();
if (clicked.getName().equals("Game1"))
else if(clicked.getName().equals("Game2"))
else if(clicked.getName().equals("Credits"))
else if(clicked.getName().equals("Exit"))
System.exit(0);
这是我的代码，当我执行它时，NetBeans 输出区域出现以下错误。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at oops.HumanBenchmarkApp.actionPerformed(HumanBenchmarkApp.java:56)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6539)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6304)
at java.awt.Container.processEvent(Container.java:2239)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2297)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476)
at java.awt.Container.dispatchEventImpl(Container.java:2283)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84)
at java.awt.EventQueue$4.run(EventQueue.java:733)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
控制台出现错误，JFrame 甚至没有关闭。
【问题讨论】：
我很确定你应该使用getText() 而不是 getName()。 getName() 返回从不显示在窗口中的 internal 文本，默认为 null。也就是说，Agzam 的建议比使用一种大型 actionPerformed 方法要好。
不，兄弟，我只需要在帧之间切换的内部文本
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【参考方案1】：
如果你可以使用 lambda 表达式，我真的不明白为什么 ActionListener 的实现如此令人困惑：
...
Game1.addActionListener(this);
Game2.addActionListener(this);
Credits.addActionListener(this);
Exit.addActionListener(e -> // <---- NEW HERE
System.exit(0); // <---- NEW HERE
); // <---- NEW HERE
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.anchor = GridBagConstraints.NORTH;
Content.add(Title, gbc);
gbc.anchor = GridBagConstraints.CENTER;
gbc.fill = GridBagConstraints.HORIZONTAL;
JPanel Buttons = new JPanel(new GridBagLayout());
...
编辑：
或者你可以这样做：
Exit.addActionListener(new ActionListener()
@Override
public void actionPerformed(ActionEvent arg0)
System.exit(0);
);
或： 您不必比较名称，您可以比较对象引用：
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class HumanBenchmarkApp implements ActionListener
JFrame appWindow, reflexFrame, visualFrame, creditsFrame;
JLabel title;
JButton game1, game2, credits, exit;
public HumanBenchmarkApp()
appWindow = new JFrame("Human Benchmark");
appWindow.setSize(400, 400);
JPanel content = new JPanel();
content.setBorder(new EmptyBorder(10, 10, 10, 10));
content.setLayout(new GridBagLayout());
try
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
catch(Exception e)
System.err.println(e.getMessage());
appWindow.setLayout(new BoxLayout(appWindow.getContentPane(),BoxLayout.Y_AXIS));
title = new JLabel("<html><h1><strong>Human Benchmark App</strong></h1><br></html>");
game1 = new JButton("<html><h4>Reflex Action Test</h4></html>");
game2 = new JButton("<html><h4>Visual Memory Test</h4></html>");
credits = new JButton("<html><h4>Credits</h4></html>");
exit = new JButton("<html><h4>Exit</h4></html>");
game1.addActionListener(this);
game2.addActionListener(this);
credits.addActionListener(this);
exit.addActionListener(this);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.anchor = GridBagConstraints.NORTH;
content.add(title, gbc);
gbc.anchor = GridBagConstraints.CENTER;
gbc.fill = GridBagConstraints.HORIZONTAL;
JPanel Buttons = new JPanel(new GridBagLayout());
Buttons.add(game1, gbc);
Buttons.add(game2, gbc);
Buttons.add(credits, gbc);
Buttons.add(exit, gbc);
gbc.weighty = 1;
content.add(Buttons);
appWindow.add(content);
appWindow.setVisible(true);
appWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
public static void main(String[] args)
new HumanBenchmarkApp();
@Override
public void actionPerformed(ActionEvent e)
JButton clicked = (JButton)e.getSource();
if (clicked == game1)
else if(clicked == game2)
else if(clicked == credits)
else if(clicked == exit)
System.exit(0);
【讨论】：
完美！！！！ @Agzam 我听说过 lambda 表达式，但我们的老师没有教我们这些，所以我用基本的简单实现做了 @20CSE028 Afsal Baaqir A，我已编辑答案并添加了 2 个变体【参考方案2】：问题是您的按钮退出的名称不是“退出”。这是你的代码：
Exit = new JButton("<html><h4>Exit</h4></html>");
相反，您可以比较退出和单击是否与 Agzam 描述的按钮相同。
@Override
public void actionPerformed(ActionEvent e)
JButton clicked = (JButton)e.getSource();
if (clicked == game1)
else if(clicked == game2)
else if(clicked == credits)
else if(clicked == exit)
System.exit(0);
【讨论】：
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