Java 多按钮Swing的ActionListener

我想使用相同的EventHandler处理多个按钮的操作。单击按钮时，标签的文本将相应更改

此代码显示了

public class string implements ActionListener{

    JLabel jlab;

    public void actionPerformed(ActionEvent Ae){
         jlab.setText(Ae.getActionCommand());
     }

        public static void main(String args[]){
            JFrame j = new JFrame("HP");
            j.setSize(300,300);
            j.setLayout(new FlowLayout());
            j.setDefaultCloseOperation(j.EXIT_ON_CLOSE);
            j.setVisible(true);    

        jlab=new JLabel("Here");
        j.add(jlab);

            JButton j1=new JButton("Button1");
            j1.setActionCommand("Your pressed Button 1");

            j1.addActionListener(this );

            j.add(j1);

            JButton j2=new JButton("Button2");
            j2.setActionCommand("Your pressed Button 1");
            j2.addActionListener(this );
            j.add(j2);
    }
   }

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如何更正此代码？

了解变量是什么以及它是如何工作的非常重要。不能从非静态上下文引用静态变量

Non static variable this cannot be referenced from a static context. 

---

您的问题有两种解决方案：

使用构造函数

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

import java.awt.FlowLayout;

public class Stackoverflow implements ActionListener{

    private JLabel jlab; /* It's a good practice to make your variables private or protected */



    public static void main(String args[]){
        new Stackoverflow();
    }
    public Stackoverflow(){
            JFrame j = new JFrame("HP");
            j.setSize(300,300);
            j.setLayout(new FlowLayout());
            j.setDefaultCloseOperation(j.EXIT_ON_CLOSE);
            j.setVisible(true);    

            jlab=new JLabel("Here");
            j.add(jlab);

            JButton j1=new JButton("Button1");
            j1.setActionCommand("Your pressed Button 1");

            j1.addActionListener(this );

            j.add(j1);

            JButton j2=new JButton("Button2");
            j2.setActionCommand("Your pressed Button 2");
            j2.addActionListener(this );
            j.add(j2);
    }
    public void actionPerformed(ActionEvent Ae){
         jlab.setText(Ae.getActionCommand());
    }
}

或者，在main中创建同一类的对象，并将其传递给

addActionListener

方法。还要使JLabel为静态

    public class buttons1 implements ActionListener{

        JLabel jlab;

        buttons1(){


                JFrame j = new JFrame("HP");
                j.setSize(300,300);
                j.setLayout(new FlowLayout());
                j.setDefaultCloseOperation(j.EXIT_ON_CLOSE);
                j.setVisible(true);    

                jlab=new JLabel("Here");
                j.add(jlab);

                JButton j1=new JButton("Button1");
                j1.setActionCommand("Your pressed Button 1");

                j1.addActionListener(this );

                j.add(j1);

                JButton j2=new JButton("Button2");
                j2.setActionCommand("Your pressed Button 2");
                j2.addActionListener(this );
                j.add(j2);


        }

        public void actionPerformed(ActionEvent Ae){

                  jlab.setText(Ae.getActionCommand());

        }



        public static void main(String args[]){
            new buttons1();
        } }  

---

main方法中的大部分内容应该移动到构造函数或非静态的

init（）

方法中。这将解决眼前的问题-因为

这个
将存在。另请参阅
public class buttons2 implements ActionListener{
    static JLabel jlab;

    public void actionPerformed(ActionEvent Ae){

                             jlab.setText(Ae.getActionCommand());

                         }



    public static void main(String args[]){

        buttons2 s = new  buttons2();

        JFrame j = new JFrame("HP");
            j.setSize(300,300);
            j.setLayout(new FlowLayout());
            j.setDefaultCloseOperation(j.EXIT_ON_CLOSE);
            j.setVisible(true);    

            jlab=new JLabel("Here");
            j.add(jlab);

            JButton j1=new JButton("Button1");
            j1.setActionCommand("Your pressed Button 1");

            j1.addActionListener(s);

            j.add(j1);

            JButton j2=new JButton("Button2");
            j2.setActionCommand("Your pressed Button 2");
            j2.addActionListener(s);
            j.add(j2);
       }
   }