ActionListener未实现 [英] ActionListener isn't Implementing

问题描述

JFrameWithPanel不是抽象的，不会覆盖java.awt.event.ActionListener中的抽象方法actionPerformed（java.awt.event.ActionEvent）
公共类JFrameWithPanel扩展JFrame实现ActionListener

JFrameWithPanel is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener public class JFrameWithPanel extends JFrame implements ActionListener

我没有得到这段代码。 Book和Java站点告诉我这是该方法的语法，但这个错误再次出现。

I Don't get this code. Book and Java site tells me this is the syntax for the method, but again this error shows up constantly.

import javax.swing.*;
import javax.swing.JOptionPane;
import java.awt.*;
import java.awt.event.*;
import java.lang.Math.*;
import java.lang.Integer.*;
import java.util.*;
import java.util.Random;
import java.io.*;
import java.text.*;
import java.text.DecimalFormat.*;

public class JFrameWithPanel extends JFrame implements ActionListener
{
 JButton button = new JButton("Exit");

 public JFrameWithPanel()
 {
  super("JFrame with Panel");

  JComboBox packageChoice = new JComboBox();
  packageChoice.addItem("A+ Certification");
  packageChoice.addItem("Network+ Certification ");
  packageChoice.addItem("Security+ Certifictation");
  packageChoice.addItem("CIT Full Test Package");

  packageChoice.addActionListener(this);

  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  JPanel pane = new JPanel();
  pane.add(button);
  pane.add(packageChoice);
  setContentPane(pane);
  setSize(200,100);
  setVisible(true);

 }
}

然后是

public class CreateJFrameWithPanel
{
 public static void main(String[] args)
 {
  JFrameWithPanel panel = new JFrameWithPanel();
 }
}

推荐答案

class实现 ActionListener 界面。这意味着它必须实现一个方法：

The class implements the ActionListener interface. This means that it must implement a method:

public void actionPerformed(ActionEvent)

但是，您发布的类定义不包括此方法，因此您看到编译错误的原因。要修复代码，请尝试添加以下方法：

However, the class definition you've posted does not include this method, hence why you are seeing a compilation error. To fix the code, try adding the following method:

public void actionPerformed(ActionEvent evt) {
  Object obj = packageChoice.getSelectedItem();
  JOptionPane.showMessageDialog(this, "You selected: " + obj);
}

这篇关于ActionListener未实现的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！