英文:
Using a JPanel to display different info, but it can only be shown the 1st time
问题
我是新手使用Java GUI，正在学习创建JPanel，然后使用同一个面板在其上切换不同的内容。当我第一次单击按钮时，信息显示出来，如果我单击"返回"按钮然后再次单击"领导力培训"按钮，什么都不会显示出来。我尝试在allContentPanel()上使用removeAll()、repaint()和revalidate()，但不起作用。
import java.util.*;
import javax.swing.*;
import java.awt.*;
import java.awt.Image;
import java.awt.event.*;
import java.text.*;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.Clip;
import javax.sound.sampled.AudioSystem;
import java.io.File;
public class Execute extends JFrame implements ActionListener
{
private static CardLayout cardLayout = new CardLayout();
private static JPanel cardPanels, panelMenu, panelInfo, panelSub, allContentPanel;
private static JScrollPane scrollpane1;
private static Font titleFont = new Font(Font.DIALOG, Font.BOLD, 30);
private static Font contentFont = new Font(Font.DIALOG, Font.PLAIN, 20);
private static Font spacingFont = new Font(Font.DIALOG, Font.PLAIN, 5);
private static ArrayList<JTextArea> info, leadershipInfo, timeInfo;
public Execute()
{
super("Training Management System");
setSize(1500, 800);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
init();
setVisible(true);
}
public static void main(String[] args)
{
new Execute();
}
public void init()
{
cardPanels = new JPanel();
cardPanels.setLayout(cardLayout);
allContentPanel = new JPanel();
panelMenu = new JPanel(null);
panelInfo = new JPanel(null);
panelSub = new JPanel(null);
cardPanels.add(panelMenu, "menu");
cardPanels.add(panelInfo, "infoMenu");
cardPanels.add(panelSub, "subInfo");
add(cardPanels);
leadershipInfo = new ArrayList<JTextArea>();
leadershipInfo.add(new JTextArea(" 1. 理解情感智能及如何在职场中展示。"));
leadershipInfo.add(new JTextArea(" 2. 培养自我意识，学习如何建立有意义的人际关系。"));
leadershipInfo.add(new JTextArea(" 3. 理解如何建立和维护领导力存在感。"));
leadershipInfo.add(new JTextArea(" 4. 深入研究领导力的要点，比如如何激励团队。"));
leadershipInfo.add(new JTextArea(" 5. 学习管理的基本要点，比如如何有效沟通。"));
leadershipInfo.add(new JTextArea(" 6. 理解如何将领导模型在个人、地方和全球范围内付诸实践。"));
leadershipInfo.add(new JTextArea(" 7. 更深入地了解自己的个人身份以及如何塑造自己的领导和跟随身份。"));
leadershipInfo.add(new JTextArea(" 优秀的领导者是对自己的工作充满激情和信心的人，他们在过程中激励着其他人。提高自我意识，增强自信，能够给人留下深刻印象。掌握团队工作、沟通以及如何在工作中激励团队的实际知识。无论您是新手还是经验丰富，这门课程都是一个有用且信息丰富的指南。我们的学习材料全天候提供，随时随地供全球学生使用，非常方便。这些密集的在线课程向所有人开放，只要您对该主题感兴趣！我们提供世界一流的学习材料，因此您可以放心，材料具有高质量、准确和最新的特点。"));
showMenu();
}
public void showMenu()
{
panelMenu.setBackground(new Color(1, 121, 111));
JButton buttonCI = new JButton("查看课程信息");
panelMenu.add(buttonCI);
buttonCI.setBounds(550, 230, 400, 80);
buttonCI.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
cardLayout.show(cardPanels, "infoMenu");
}
});
JButton buttonTT = new JButton("查看时间表");
panelMenu.add(buttonTT);
buttonTT.setBounds(550, 340, 400, 80);
JButton buttonTMP = new JButton("跟踪我的进展");
panelMenu.add(buttonTMP);
buttonTMP.setBounds(550, 450, 400, 80);
showSubMenu();
}
public void showSubMenu()
{
panelInfo.setBackground(new Color(1, 121, 111));
JButton buttonLT = new JButton("领导力培训");
panelInfo.add(buttonLT);
buttonLT.setBounds(550, 120, 400, 80);
buttonLT.addActionListener(this);
JButton buttonTM = new JButton("时间管理");
panelInfo.add(buttonTM);
buttonTM.setBounds(550, 230, 400, 80);
JButton buttonEC = new JButton("有效沟通");
panelInfo.add(buttonEC);
buttonEC.setBounds(550, 340, 400, 80);
JButton buttonPM = new JButton("项目管理");
panelInfo.add(buttonPM);
buttonPM.setBounds(550, 450, 400, 80);
JButton buttonDT = new JButton("多元化培训");
panelInfo.add(buttonDT);
buttonDT.setBounds(550, 560, 400, 80);
JButton buttonBack = new JButton("返回");
panelInfo.add(buttonBack);
buttonBack.setBounds(20, 650, 80, 80);
buttonBack.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
cardLayout.show(cardPanels, "menu");
}
});
}
public void showPanelSub()
{
panelSub.setBackground(new Color(1, 121, 111));
JButton buttonBack = new JButton("返回");
panelSub.add(buttonBack);
buttonBack.setBounds(20, 650, 80, 80);
buttonBack.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
cardLayout.show
<details>
<summary>英文:</summary>
I am new to Java GUI, and learning to create a `JPanel`, then use the same panel to switch different content on it. When I click on the button for the first time, the information showed up and if I click the button "back" and click the button "Leadership Training" again, nothing showed up. I have tried to use `removeAll()`, `repaint()` and `revalidate()` on `allContentPanel()` but it won't work.
import java.util.*;
import javax.swing.*;
import java.awt.*;
import java.awt.Image;
import java.awt.event.*;
import java.text.*;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.Clip;
import javax.sound.sampled.AudioSystem;
import java.io.File;
public class Execute extends JFrame implements ActionListener
{
private static CardLayout cardLayout = new CardLayout();
private static JPanel cardPanels,panelMenu,panelInfo,panelSub,allContentPanel;
private static JScrollPane scrollpane1;
private static Font titleFont = new Font(Font.DIALOG,Font.BOLD,30);
private static Font contentFont = new Font(Font.DIALOG,Font.PLAIN,20);
private static Font spacingFont = new Font(Font.DIALOG,Font.PLAIN,5);
private static ArrayList<JTextArea> info,leadershipInfo,timeInfo;
public Execute()
{
super("Training Management System");
setSize(1500,800);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
init();
setVisible(true);
}
public static void main(String[] args)
{
new Execute();
}
public void init()
{
cardPanels = new JPanel();
cardPanels.setLayout(cardLayout);
allContentPanel = new JPanel();
panelMenu = new JPanel(null);
panelInfo = new JPanel(null);
panelSub = new JPanel(null);
cardPanels.add(panelMenu,"menu");
cardPanels.add(panelInfo,"infoMenu");
cardPanels.add(panelSub,"subInfo");
add(cardPanels);
leadershipInfo = new ArrayList <JTextArea> ();
leadershipInfo.add(new JTextArea(" 1. Understand emotional intelligence and how to demonstrate it in the workplace."));
leadershipInfo.add(new JTextArea(" 2. Become self-aware and learn how to build meaningful relationships."));
leadershipInfo.add(new JTextArea(" 3. Understand how to build and maintain leadership presence."));
leadershipInfo.add(new JTextArea(" 4. Study in depth the essentials of leadership, like how to motivate your team."));
leadershipInfo.add(new JTextArea(" 5. Go through management essentials, like how to communicate effectively."));
leadershipInfo.add(new JTextArea(" 6. Understand how leadership models are put into practice personally, locally, and globally."));
leadershipInfo.add(new JTextArea(" 7. Gain a greater understanding of their own personal identities and how their identities shape their leadership " + "\n and followership."));
leadershipInfo.add(new JTextArea(" Great leaders are individuals who are passionate and confident about their work, and they inspire others in the " +
"\n process. Become self-aware, confident and able to make a great first impression. Gain practical knowledge of " +
"\n team work, communication and how to motivate your team at work. Whether you are new to management or " +
"\n have plenty of experience, this course is a helpful and informative guide. Our learning material is available to " +
"\n students 24/7 anywhere in the world, so it is extremely convenient. These intensive online courses are open to " +
"\n everyone, as long as you have an interest in the topic! We provide world-class learning, so you can be assured " +
"\n that the material is high quality, accurate and up-to-date."));
showMenu();
}
public void showMenu()
{
panelMenu.setBackground(new Color(1,121,111));
JButton buttonCI = new JButton ("View Course Info");
panelMenu.add(buttonCI);
buttonCI.setBounds(550,230,400,80);
buttonCI.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
cardLayout.show(cardPanels,"infoMenu");
}
});
JButton buttonTT = new JButton ("View Timetable");
panelMenu.add(buttonTT);
buttonTT.setBounds(550,340,400,80);
JButton buttonTMP = new JButton ("Track My Progress");
panelMenu.add(buttonTMP);
buttonTMP.setBounds(550,450,400,80);
showSubMenu();
}
public void showSubMenu()
{
panelInfo.setBackground(new Color(1,121,111));
JButton buttonLT = new JButton ("Leadership Training");
panelInfo.add(buttonLT);
buttonLT.setBounds(550,120,400,80);
buttonLT.addActionListener(this);
JButton buttonTM = new JButton ("Time Management");
panelInfo.add(buttonTM);
buttonTM.setBounds(550,230,400,80);
JButton buttonEC = new JButton ("Effective Communication");
panelInfo.add(buttonEC);
buttonEC.setBounds(550,340,400,80);
JButton buttonPM = new JButton ("Project Management");
panelInfo.add(buttonPM);
buttonPM.setBounds(550,450,400,80);
JButton buttonDT = new JButton ("Diversity Training");
panelInfo.add(buttonDT);
buttonDT.setBounds(550,560,400,80);
JButton buttonBack = new JButton ("Back");
panelInfo.add(buttonBack);
buttonBack.setBounds(20,650,80,80);
buttonBack.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
cardLayout.show(cardPanels,"menu");
}
});
}
public void showPanelSub()
{
panelSub.setBackground(new Color(1,121,111));
JButton buttonBack = new JButton ("Back");
panelSub.add(buttonBack);
buttonBack.setBounds(20,650,80,80);
buttonBack.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
cardLayout.show(cardPanels,"infoMenu");
}
});
allContentPanel.setBackground(Color.WHITE);
BoxLayout boxlayout = new BoxLayout(allContentPanel, BoxLayout.Y_AXIS);
allContentPanel.setLayout(boxlayout);
JTextArea outcomeTitle = new JTextArea(" Learning Outcome");
JTextArea spacing1 = new JTextArea(" ");
JTextArea spacing2 = new JTextArea(" ");
JTextArea introTitle = new JTextArea(" Subject Introduction");
JTextArea spacing3 = new JTextArea(" ");
infoFormat(outcomeTitle,"title");
infoFormat(spacing1,"spacing");
infoFormat(info.get(0),"content");
infoFormat(info.get(1),"content");
infoFormat(info.get(2),"content");
infoFormat(info.get(3),"content");
infoFormat(info.get(4),"content");
infoFormat(info.get(5),"content");
infoFormat(info.get(6),"content");
infoFormat(spacing2,"content");
infoFormat(introTitle,"title");
infoFormat(spacing3,"spacing");
infoFormat(info.get(7),"content");
scrollpane1 = new JScrollPane(allContentPanel,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
scrollpane1.setBounds(250,150,1000,500);
panelSub.add(scrollpane1);
}
public void infoFormat(JTextArea text, String type)
{
if (type.equals("title"))
text.setFont(titleFont);
else if (type.equals("content"))
text.setFont(contentFont);
else if (type.equals("spacing"))
text.setFont(spacingFont);
text.setEditable(false);
text.setLineWrap(true);
text.setWrapStyleWord(true);
allContentPanel.add(text);
}
public void actionPerformed(ActionEvent e)
{
if (e.getActionCommand().equals("Leadership Training"))
{
info = leadershipInfo;
}
else if (e.getActionCommand().equals("Time Management"))
{ //will continue when get the first successful
}
else if (e.getActionCommand().equals("Effective Communication"))
{ //will continue when get the first successful
}
else if (e.getActionCommand().equals("Project Management"))
{ //will continue when get the first successful
}
else if (e.getActionCommand().equals("Diversity Training"))
{ //will continue when get the first successful
}
showPanelSub();
cardLayout.show(cardPanels,"subInfo");
}
}
</details>
# 答案1
**得分**: 2
public class execute extends JFrame implements ActionListener
1 - 类名应以大写字母开头。所有JDK类都遵循此标准。通过示例来学习。
2 - 你不应该扩展JFrame。只有在你想要向该类添加新功能时才扩展类。向框架添加组件或与应用程序相关的逻辑不会改变框架的功能。
private static CardLayout cardLayout = new CardLayout();
不要使用静态变量。这不是static关键字的用途。这些变量应该是类的实例变量。
public static void main(String[] args)
{
new execute();
}
所有Swing组件应该在“事件分发线程（EDT）”上创建。
panelMenu = new JPanel(null);
...
buttonLT.setBounds(550,120,400,80);
不要使用null布局。Swing设计用于与布局管理器一起使用。
public void actionPerformed(ActionEvent e)
这个方法中的代码如何编译？我看到很多“{”，但没有“}”。
if (type == "title")
不要使用“==”进行对象比较。而是使用`equals(...)`方法。
**这可能是问题的原因，因为if条件将不会按照您的期望工作**
我建议您首先阅读[Swing教程](https://docs.oracle.com/javase/tutorial/uiswing/TOC.html)，以了解Swing基础知识，以帮助您应对上述建议。
特别是以下部分：
1. `Swing中的并发性` - 有关EDT的信息
2. `如何使用CardLayout` - 有关如何更好地组织代码以避免扩展JFrame和正确使用静态变量的示例。
3. `布局管理器的可视化指南`
编辑：
我所做的第一个更改是在showSubPane()方法中添加了一个removeAll()语句：
panelSub.setBackground(new Color(1,121,111));
panelSub.removeAll(); // 添加了
这确实有所作为，尽管它实际上在顶部显示了更多信息。
接下来，我添加了：
allContentPanel = new JPanel(); // 添加了
allContentPanel.setBackground(Color.WHITE);
现在内容看起来一样。
然而，我认为整体方法需要更改。
你不应该需要不断添加/删除或创建新组件来动态重建面板。
更好的方法是将文本存储在HTML文件中，然后只需加载带有来自适当文件的数据的JEditorPane。这将使文本显示更容易维护和更新。
<details>
<summary>英文:</summary>
public class execute extends JFrame implements ActionListener
1 - Class names should start with an upper case character. All JDK class follow this standard. Learn by example.
2 - You should not extend JFrame. You extend a class when you want to add new functionality to that class. Add components to a frame or logic related to you application does not change the functionality of the frame.
private static CardLayout cardLayout = new CardLayout();
Don't use static variables. That is not what the static keyword is used for. The variables should be instance variables in your class.
public static void main(String[] args)
{
new execute();
}
All Swing components should be created on the `Event Dispatch Thread (EDT)`
panelMenu = new JPanel(null);
...
buttonLT.setBounds(550,120,400,80);
Don't use null layout. Swing was designed to be used with layout managers.
public void actionPerformed(ActionEvent e)
How does the code in this method even compile? I see lots of opening "{" but no ending "}".
if (type == "title")
Don't use "==" for object comparison. Instead you use the `equals(...)` method.
**This could be the problem since the if condition will not work the way you expect**
I suggest you start by reading the [Swing Tutorial](https://docs.oracle.com/javase/tutorial/uiswing/TOC.html) for Swing basics to help with the above suggestions.
In particular the sections on:
1. `Concurrency in Swing` - for information about the EDT
2. `How to Use CardLayout` - for examples on how to better structure your code so you don't extend a JFrame and the proper usage of static variables.
3. `A Visual Guide to Layout Managers`
Edit:
The first change I made was to add a removeAll() statement in the showSubPane() method:
panelSub.setBackground(new Color(1,121,111));
panelSub.removeAll(); // added
That did something, although it actually showed more information at the top.
Next I then added:
allContentPanel = new JPanel(); // added
allContentPanel.setBackground(Color.WHITE);
Now the content looks the same.
However, I think the overall approach needs to be changed.
You should not need to be continually adding/removing or creating new components to dynamically rebuild the panels.
A better approach would be to store the text in an HTML file and then just load a JEditorPane with the data from the appropriate file. This will allow for easier maintenance and updating of the text displayed.
</details>
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