Question

警告：初学者编程试图理解她的作业!!会问愚蠢的问题！

import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;


public class StudentGUI extends JFrame implements ActionListener {
    public StudentGUI()
    {
            super("StudentGUI Frame");



      //TopPanel
     TopPanel tp;
     tp=new TopPanel();

     Dimension d = new Dimension(800,600);
     tp.setPreferredSize(d);
     this.add (tp, BorderLayout.NORTH);
     tp.setVisible(true);
     this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     this.setSize(800,600);
        setBackground(Color.PINK);

        tp.setVisible(true);

        //TopPanel End


        //BottomPanel
        BottomPanel bp;
     bp=new BottomPanel();


     this.add (bp, BorderLayout.SOUTH);
     tp.setVisible(true);
     this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     this.setSize(800,600);



        //BottomPanel End

        //MiddlePanel 

    MiddlePanel mp;
     mp=new MiddlePanel();


     this.add (mp, BorderLayout.CENTER);
     mp.setVisible(true);
     this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     this.setSize(800,600);

        //MiddlePanel End



        this.setVisible(true);


    }

    exitBtn.addActionListener(new ActionListener() {


    @Override
    public void actionPerformed(ActionEvent e){


  int selectedOption = JOptionPane.showConfirmDialog(null, 
                              "Do you want to close the window?", 
                              "Choose", 
                              JOptionPane.YES_NO_OPTION); 
    if (selectedOption == JOptionPane.YES_OPTION) {
        System.exit(1));



}
}
 }
    public static void main(String[] args)
    {
        new StudentGUI();
    }


}

这是我的主要框架代码。

这是我的面板代码，其中包含退出按钮。

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.*;

public class BottomPanel extends JPanel {

public String findbtn="";
public String insertBtn="";
public String updateBtn="";
public String deleteBtn="";
public String exitBtn="";

public BottomPanel() {
   JButton findbtn;
     findbtn=new JButton("Find");
        add(findbtn);

           JButton insertBtn;
     insertBtn=new JButton("Insert");
        add(insertBtn);

           JButton updateBtn;
     updateBtn=new JButton("Update");
        add(updateBtn);

           JButton deleteBtn;
     deleteBtn=new JButton("Delete");
        add(deleteBtn);

        JButton exitBtn;
     exitBtn=new JButton("Exit");
        add(exitBtn);
         exitBtn.addActionListener;


}
}

我一遍又一遍地试着让退出按钮工作，一半时间程序工作但是当我按下退出按钮时没有任何反应。我想要让它达到我点击退出按钮的程度，它询问我是否确定要退出，如果我不推它不会，如果我推它是的确如此。

Answer 1

我清理了所有面板，只留下底部面板用于演示。在BottomPanel中，我将所有公共字符串修复为公共JButton。正如帕特指出的那样，exitbtn应该属于某种东西，我让它属于BottomPanel。您实际上不需要在JFrame中实现接口ActionListener。这是StudentGUI的代码

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JOptionPane;


public class StudentGUI extends JFrame {
    private static final long serialVersionUID = 1L;

    public StudentGUI()
    {
        super("StudentGUI Frame");

        Dimension d = new Dimension(800,600);

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800,600);
        setBackground(Color.PINK);
        this.setVisible(true);


        //BottomPanel
        BottomPanel bp;
        bp=new BottomPanel();
        this.add (bp, BorderLayout.SOUTH);

        bp.exitBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e){
                int selectedOption = JOptionPane.showConfirmDialog(null, "Do you want to close the window?",    "Choose",   JOptionPane.YES_NO_OPTION); 
                if (selectedOption == JOptionPane.YES_OPTION) 
                    System.exit(1);
                return;
            }
        });
    }

    public static void main(String[] args)
    {
        new StudentGUI();
    }

}

以下是BottomPanel的代码：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.*;

public class BottomPanel extends JPanel {

    public JButton findbtn;
    public JButton insertBtn;
    public JButton updateBtn;
    public JButton deleteBtn;
    public JButton exitBtn;

    public BottomPanel() {
        findbtn=new JButton("Find");
        add(findbtn);
        insertBtn=new JButton("Insert");
        add(insertBtn);
        updateBtn=new JButton("Update");
        add(updateBtn);
        deleteBtn=new JButton("Delete");
        add(deleteBtn);
        exitBtn=new JButton("Exit");
        add(exitBtn);



    }
}

这绝对不是最佳做法，但至少它是有效的。

Answer 2

我在评论中解释了我的所有更改，只要您的TopPanel和MiddlePanel类没有问题，这应该有效。我在测试它时只是注释掉了那些线。

将第一堂课改为

import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

// removed implements ActionListener
public class StudentGUI extends JFrame {
    public StudentGUI() {
        super("StudentGUI Frame");

        //TopPanel
        TopPanel tp;
        tp=new TopPanel();
        Dimension d = new Dimension(800,600);
        tp.setPreferredSize(d);
        this.add (tp, BorderLayout.NORTH);
        tp.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800,600);
        setBackground(Color.PINK);
        tp.setVisible(true);
        //TopPanel End

        //BottomPanel
        BottomPanel bp;
        bp=new BottomPanel();
        this.add (bp, BorderLayout.SOUTH);
        tp.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800,600);
        //BottomPanel End

        //MiddlePanel 
        MiddlePanel mp;
        mp=new MiddlePanel();
        this.add (mp, BorderLayout.CENTER);
        mp.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800,600);
        //MiddlePanel End

        this.setVisible(true);

        /* moved action listener within method, 
         * used bp.exitBtn instead of exitBtn
         */
        bp.exitBtn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e){
                    int selectedOption =
                        JOptionPane.showConfirmDialog(null, 
                                                      "Do you want to close the window?", 
                                                      "Choose", 
                                                      JOptionPane.YES_NO_OPTION); 
                    if (selectedOption == JOptionPane.YES_OPTION) {
                        System.exit(1);
                    }
                }
            }); // fixed braces, the closing paren should go here

    }

    public static void main(String[] args) {
        new StudentGUI();
    }
}

你的第二堂课应该是

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.*;

public class BottomPanel extends JPanel {
    /* instead of strings, added references to JButtons
     * so that they can be accessed from other classes
     */
    public JButton findbtn;
    public JButton insertBtn;
    public JButton updateBtn;
    public JButton deleteBtn;
    public JButton exitBtn;

    public BottomPanel() {
        findbtn=new JButton("Find");
        add(findbtn);

        insertBtn=new JButton("Insert");
        add(insertBtn);

        updateBtn=new JButton("Update");
        add(updateBtn);

        deleteBtn=new JButton("Delete");
        add(deleteBtn);

        exitBtn=new JButton("Exit");
        add(exitBtn);
    }
}

Answer 3

我正在写我的答案，但我被打败了。我建议你使用IDE作为IDE。你的错误不是编程错误。他们是基本的酒吧。（我们所有人都去过:-D）

在这里下载eclipse - ＆gt; https://eclipse.org/downloads/packages/eclipse-standard-432/keplersr2

红色下划线的东西是错误的。如果它以黄色加下划线通常表示它没有被使用。这有望减少您寻找缺少的berracts的时间。

享受并继续学习:)

退出按钮无法从框架到面板

3 个答案: