Java Applet 错误 - IllegalArgumentException“将容器的父级添加到自身”
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时间：2020-10-31 09:07:05 来源:igfitidea点击:
Java Applet Error - IllegalArgumentException "adding container's parent to itself"
提问by Sarang
I have to create an applet. The code I have written is as follows.
我必须创建一个小程序。我写的代码如下。
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class feedback extends JApplet
implements ActionListener
{
private JTextField login;
private JTextField email;
private JTextField comments;
private final String SUBMIT="SUBMIT";
private final String CLEAR="CLEAR";
public void actionPerformed(ActionEvent e)
{
String command = e.getActionCommand();
if(CLEAR.equals(command))
{login.setText(" ");
email.setText(" ");
comments.setText(" ");}
else if(SUBMIT.equals(command))
{
login.setText(" ");
email.setText(" ");
comments.setText(" ");
}
}
public void start()
{
Container contentPane = getContentPane();
JScrollPane sPane = new JScrollPane();
JPanel pContPanel = new JPanel();
pContPanel.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints(3, 4, 1, 1, 0, 0, GridBagConstraints.CENTER, GridBagConstraints.HORIZONTAL, new Insets(10,10,10,10), 20, 20);
JLabel title = new JLabel("FEEDBACK");
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 0;
gbc.gridwidth = 3;
pContPanel.add(title, gbc);
JPanel panel1 = new JPanel();
JLabel prompt = new JLabel("LOGIN");
panel1.add(prompt, gbc);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 1;
gbc.gridwidth = 1;
pContPanel.add(panel1, gbc);
login = new JTextField(15);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 1;
gbc.gridwidth = 2;
pContPanel.add(login, gbc);
JPanel panel2=new JPanel();
JLabel print = new JLabel("EMAIL");
panel2.add(panel2);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 2;
gbc.gridwidth = 1;
pContPanel.add(panel2, gbc);
email = new JTextField(30);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 2;
gbc.gridwidth = 2;
pContPanel.add(email, gbc);
JPanel panel3=new JPanel();
JLabel ask = new JLabel("COMMENTS");
panel3.add(panel3);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 3;
gbc.gridwidth = 1;
pContPanel.add(panel3, gbc);
comments = new JTextField(50);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 3;
gbc.gridwidth = 2;
pContPanel.add(comments, gbc);
JButton bSUBMIT = new JButton(SUBMIT);
bSUBMIT.addActionListener(this);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 4;
gbc.gridwidth = 1;
pContPanel.add(bSUBMIT, gbc);
JButton bCLEAR = new JButton(CLEAR);
bCLEAR.addActionListener(this);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 4;
pContPanel.add(bCLEAR, gbc);
sPane.setViewportView(pContPanel);
contentPane.add(sPane, BorderLayout.CENTER);
}
}
It is being compiled with NO syntax errors. But, when I run it using an applet viewer(in BlueJ), it says,
它正在编译，没有语法错误。但是，当我使用小程序查看器（在 BlueJ 中）运行它时，它说，
exception: java.lang.IllegalArgumentException : adding container's parent to itself.
异常： java.lang.IllegalArgumentException ：将容器的父级添加到自身。
Can you please help me figure out where is the mistake in my code and in what way can I rectify it? Thank you.
你能帮我找出我的代码中的错误在哪里，我可以用什么方式纠正它？谢谢你。
回答by Satya
You are trying to add a panel to itself e.g. panel2.add(panel2);
您正在尝试向其自身添加面板，例如 panel2.add(panel2);
the correct program should be :
正确的程序应该是：
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class Feedback extends JApplet implements ActionListener
{
private JTextField login;
private JTextField email;
private JTextField comments;
private final String SUBMIT="SUBMIT";
private final String CLEAR="CLEAR";
public void actionPerformed(ActionEvent e)
{
String command = e.getActionCommand();
if(CLEAR.equals(command))
{login.setText(" ");
email.setText(" ");
comments.setText(" ");}
else if(SUBMIT.equals(command))
{
login.setText(" ");
email.setText(" ");
comments.setText(" ");
}
}
public void start()
{
Container contentPane = getContentPane();
JScrollPane sPane = new JScrollPane();
JPanel pContPanel = new JPanel();
pContPanel.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints(3, 4, 1, 1, 0, 0, GridBagConstraints.CENTER, GridBagConstraints.HORIZONTAL, new Insets(10,10,10,10), 20, 20);
JLabel title = new JLabel("FEEDBACK");
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 0;
gbc.gridwidth = 3;
pContPanel.add(title, gbc);
JPanel panel1 = new JPanel();
JLabel prompt = new JLabel("LOGIN");
panel1.add(prompt, gbc);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 1;
gbc.gridwidth = 1;
pContPanel.add(panel1, gbc);
login = new JTextField(15);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 1;
gbc.gridwidth = 2;
pContPanel.add(login, gbc);
JPanel panel2=new JPanel();
JLabel print = new JLabel("EMAIL");
panel2.add(print);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 2;
gbc.gridwidth = 1;
pContPanel.add(panel2, gbc);
email = new JTextField(30);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 2;
gbc.gridwidth = 2;
pContPanel.add(email, gbc);
JPanel panel3=new JPanel();
JLabel ask = new JLabel("COMMENTS");
panel3.add(ask);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 3;
gbc.gridwidth = 1;
pContPanel.add(panel3, gbc);
comments = new JTextField(50);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 3;
gbc.gridwidth = 2;
pContPanel.add(comments, gbc);
JButton bSUBMIT = new JButton(SUBMIT);
bSUBMIT.addActionListener(this);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 0;
gbc.gridy = 4;
gbc.gridwidth = 1;
pContPanel.add(bSUBMIT, gbc);
JButton bCLEAR = new JButton(CLEAR);
bCLEAR.addActionListener(this);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridx = 1;
gbc.gridy = 4;
pContPanel.add(bCLEAR, gbc);
sPane.setViewportView(pContPanel);
contentPane.add(sPane, BorderLayout.CENTER);
}
}
