Java 按钮操作侦听器错误

我需要帮助解决这个问题。BlueJ上的错误消息是“找不到符号变量SevenentsFrame。我是一个初学者，不知道该怎么做，已经为此代码工作了几个小时

    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import javax.swing.JFrame;
    import javax.swing.JButton;
    public class SevenContinents  extends JFrame implements ActionListener
    {
        JButton button1 = new JButton("1");
        JButton button2 = new JButton("2");
        JButton button3 = new JButton("3");
        JButton button4 = new JButton("4");
        JButton button5 = new JButton("5");
        JButton button6 = new JButton("6");
        JButton button7 = new JButton("7");

       public SevenContinents()
        {

             //BUTTONS!!!

            setSize(1500,1000);

            button1.addActionListener(this);
            button2.addActionListener(this);
            button3.addActionListener(this);
            button4.addActionListener(this);
            button5.addActionListener(this);
            button6.addActionListener(this);
            button7.addActionListener(this);

            SevenContinentsFrame.add(button1);
            SevenContinentsFrame.add(button2);
            SevenContinentsFrame.add(button3);
            SevenContinentsFrame.add(button4);
            SevenContinentsFrame.add(button5);
            SevenContinentsFrame.add(button6);
            SevenContinentsFrame.add(button7);
        }

        public void actionPerformed(ActionEvent e)
        {
            if(e.getSource == btn1)
           {
                System.out.println("You chose...");
            }
            if(e.getSource == btn2)
            {
                System.out.println("You chose...");
            }
            if(e.getSource == btn3)
            {
                System.out.println("You chose...");
            }
            if(e.getSource == btn4)
            {
                System.out.println("You chose...");
            }
            if(e.getSource == btn5)
            {
                System.out.println("You chose...");
            }
            if(e.getSource == btn6)
            {
                System.out.println("You chose...");
            }
            if(e.getSource == btn7)
            {
                System.out.println("You chose...");
            }

        }

        public static void main(String[] args)
        {
            JFrame SevenContinentsFrame = new JFrame();
            SevenContinentsFrame.setVisible(true);
            SevenContinentsFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);
        }

   } 

您正在从Swing API创建一个

JFrame

，而不是

seventions

的实例，它也是一个

JFrame

SevenContinents SevenContinentsFrame = new SevenContinents();

而这个

SevenContinentsFrame.add(button1);

您正在引用一个不存在的名称。您已在main方法中创建了一个具有该名称的变量，但它在

sevencontents

构造函数中不可见。只需删除该名称即可。例如

add(button1);
add(button2);
.
.
.

您还需要将

（）

添加到

getSource

，为操作侦听器中引用的按钮使用正确的变量名，并更改布局以使按钮显示

已更正的代码

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

public class SevenContinents extends JFrame implements ActionListener
{
    JButton button1 = new JButton("1");
    JButton button2 = new JButton("2");
    JButton button3 = new JButton("3");
    JButton button4 = new JButton("4");
    JButton button5 = new JButton("5");
    JButton button6 = new JButton("6");
    JButton button7 = new JButton("7");

    public SevenContinents()
    {

        //BUTTONS!!!
        setSize(1500, 1000);

        button1.addActionListener(this);
        button2.addActionListener(this);
        button3.addActionListener(this);
        button4.addActionListener(this);
        button5.addActionListener(this);
        button6.addActionListener(this);
        button7.addActionListener(this);

        setLayout(new FlowLayout());
        add(button1);
        add(button2);
        add(button3);
        add(button4);
        add(button5);
        add(button6);
        add(button7);
    }

    public void actionPerformed(ActionEvent e)
    {
        if (e.getSource() == button1) {
            System.out.println("You chose...");
        }
        if (e.getSource() == button2) {
            System.out.println("You chose...");
        }
        if (e.getSource() == button3) {
            System.out.println("You chose...");
        }
        if (e.getSource() == button4) {
            System.out.println("You chose...");
        }
        if (e.getSource() == button5) {
            System.out.println("You chose...");
        }
        if (e.getSource() == button6) {
            System.out.println("You chose...");
        }
        if (e.getSource() == button7) {
            System.out.println("You chose...");
        }

    }

    public static void main(String[] args)
    {
        SevenContinents SevenContinentsFrame = new SevenContinents();
        SevenContinentsFrame.setVisible(true);
        SevenContinentsFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

---

你的类名是

sevencontents

，你正在尝试访问不存在的

sevencontentsFrame

。使用

sevencontents

和viola！将所有引用更改为

sevencontentsFrame

。

这是你的完整代码。请尝试一下，这是经过测试的，如果你使用的IDE比使用BlueJ ch更好Ange是用这条线制作的

这不是JFrame这是你的类名

  JFrame SevenContinentsFrame = new JFrame();

这是什么

SevenContinentsFrame.add(button1);

另外，您并没有添加容器，最好使用数组作为按钮 容器的代码

Container cp = getContentPane();
        cp.add(pane);

最后一件事，我把你们的工具取下来，换上了，我把所有的按钮都添加到面板上

        package answer;
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;

    public class SevenContinents  extends JFrame 
    {
        public static void main(String[] args)
        {
            SevenContinents SevenContinentsFrame = new SevenContinents();
            SevenContinentsFrame.setVisible(true);

        }

        JButton button1;  
        JButton button2;  
        JButton button3;  
        JButton button4;  
        JButton button5;  
        JButton button6; 
        JButton button7; 

       public SevenContinents()
        {

             //BUTTONS!!!

            setSize(500,500);
            setDefaultCloseOperation(SevenContinents.EXIT_ON_CLOSE);

            button1 = new JButton("1");
            button2 = new JButton("2");
            button3 = new JButton("3");
            button4 = new JButton("4");
            button5 = new JButton("5");
            button6 = new JButton("6");
            button7 = new JButton("7");






            JPanel pane = new JPanel();
            pane.add(button1);
            pane.add(button2);
            pane.add(button3);
            pane.add(button4);
            pane.add(button5);
            pane.add(button6);
            pane.add(button7);

            Container cp = getContentPane();
            cp.add(pane);


            button1.addActionListener(new addButtonWatcher());
            button2.addActionListener(new addButtonWatcher());
            button3.addActionListener(new addButtonWatcher());
            button4.addActionListener(new addButtonWatcher());
            button5.addActionListener(new addButtonWatcher());
            button6.addActionListener(new addButtonWatcher());
            button7.addActionListener(new addButtonWatcher());

        }


private class addButtonWatcher implements ActionListener{
        @Override
        public void actionPerformed(ActionEvent a)
        {
            Object buttonPressed= a.getSource();
            if(buttonPressed.equals(button1))
           {

            }
            if(buttonPressed.equals(button2))
            {
                System.out.println("You chose...");
            }
            if(buttonPressed.equals(button3))
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button4)
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button5)
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button6)
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button7)
            {
                System.out.println("You chose...");
            }

        }
}


   } 

---

你还应该解释你对代码做了哪些更改，以及为什么与用户的代码相比，代码可以工作。这是一个更有效的答案，如果答案正确，可能会导致投票。

        package answer;
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;

    public class SevenContinents  extends JFrame 
    {
        public static void main(String[] args)
        {
            SevenContinents SevenContinentsFrame = new SevenContinents();
            SevenContinentsFrame.setVisible(true);

        }

        JButton button1;  
        JButton button2;  
        JButton button3;  
        JButton button4;  
        JButton button5;  
        JButton button6; 
        JButton button7; 

       public SevenContinents()
        {

             //BUTTONS!!!

            setSize(500,500);
            setDefaultCloseOperation(SevenContinents.EXIT_ON_CLOSE);

            button1 = new JButton("1");
            button2 = new JButton("2");
            button3 = new JButton("3");
            button4 = new JButton("4");
            button5 = new JButton("5");
            button6 = new JButton("6");
            button7 = new JButton("7");






            JPanel pane = new JPanel();
            pane.add(button1);
            pane.add(button2);
            pane.add(button3);
            pane.add(button4);
            pane.add(button5);
            pane.add(button6);
            pane.add(button7);

            Container cp = getContentPane();
            cp.add(pane);


            button1.addActionListener(new addButtonWatcher());
            button2.addActionListener(new addButtonWatcher());
            button3.addActionListener(new addButtonWatcher());
            button4.addActionListener(new addButtonWatcher());
            button5.addActionListener(new addButtonWatcher());
            button6.addActionListener(new addButtonWatcher());
            button7.addActionListener(new addButtonWatcher());

        }


private class addButtonWatcher implements ActionListener{
        @Override
        public void actionPerformed(ActionEvent a)
        {
            Object buttonPressed= a.getSource();
            if(buttonPressed.equals(button1))
           {

            }
            if(buttonPressed.equals(button2))
            {
                System.out.println("You chose...");
            }
            if(buttonPressed.equals(button3))
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button4)
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button5)
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button6)
            {
                System.out.println("You chose...");
            }
            if(buttonPressed == button7)
            {
                System.out.println("You chose...");
            }

        }
}


   }