Question

我刚刚开始学习如何使用swing，并且一直在关注我在网上找到的教程。我基本上按照教程＆＃34;逐字逐句地＃34;但是我得到了错误：

ScoreBoard不是抽象的，不会覆盖抽象方法 actionPerformed（ActionEvent）在ActionListener
中

所以我的问题是，如果该类不是抽象的，我如何将ActionListener实现到我的类（ScoreBoard）中？

以下是整个代码:(因为我不知道问题出在哪里）

package scoreboard;

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

public class ScoreBoard implements ActionListener{

//Class Variables
int redScore = 0;
int blueScore = 0;

//Class Objects
JPanel titlePanel, scorePanel, buttonPanel;
JLabel redLabel, blueLabel, redLabelT, blueLabelT;
JButton redButton, blueButton, resetButton;


public static void main(String[] args) {

    SwingUtilities.invokeLater(new Runnable(){
        public void run(){
            createFrame();
        }
    });

}//End Method

public static void createFrame(){

    JFrame frame = new JFrame("ScoreBoard");
    JFrame.setDefaultLookAndFeelDecorated(true);

    ScoreBoard panel = new ScoreBoard();
    frame.setContentPane(panel.contentPane());

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setResizable(false);
    frame.setSize(250, 190);
    frame.setVisible(true);

}//End Method

public JPanel contentPane(){

    JPanel basePanel = new JPanel();
    basePanel.setLayout(null);
    basePanel.setBackground(Color.black);

    //Title
    titlePanel = new JPanel();
    titlePanel.setLayout(null);
    titlePanel.setOpaque(false);
    titlePanel.setLocation(10, 0);
    titlePanel.setSize(250, 30);
    basePanel.add(titlePanel);

    redLabelT = new JLabel("Red Team");
    redLabelT.setLocation(0, 0);
    redLabelT.setSize(100, 30);
    redLabelT.setForeground(Color.red);
    redLabelT.setHorizontalAlignment(0);
    titlePanel.add(redLabelT);

    blueLabelT = new JLabel("Blue Team");
    blueLabelT.setLocation(120, 0);
    blueLabelT.setSize(100, 30);
    blueLabelT.setForeground(Color.blue);
    blueLabelT.setHorizontalAlignment(0);
    titlePanel.add(blueLabelT);

    //Score
    scorePanel = new JPanel();
    scorePanel.setLayout(null);
    scorePanel.setOpaque(false);
    scorePanel.setLocation(10, 40);
    scorePanel.setSize(250, 30);
    basePanel.add(scorePanel);

    redLabel = new JLabel("" + redScore);
    redLabel.setLocation(0, 0);
    redLabel.setSize(100, 30);
    redLabel.setForeground(Color.white);
    redLabel.setHorizontalAlignment(0);
    scorePanel.add(redLabel);

    blueLabel = new JLabel("" + blueScore);
    blueLabel.setLocation(120, 0);
    blueLabel.setSize(100, 30);
    blueLabel.setForeground(Color.white);
    blueLabel.setHorizontalAlignment(0);
    scorePanel.add(blueLabel);

    //Buttons
    buttonPanel = new JPanel();
    buttonPanel.setLayout(null);
    buttonPanel.setOpaque(false);
    buttonPanel.setLocation(10, 80);
    buttonPanel.setSize(250, 70);
    basePanel.add(buttonPanel);

    redButton = new JButton("Red Score");
    redButton.setLocation(0, 0);
    redButton.setSize(100, 30);
    redButton.addActionListener(this);
    buttonPanel.add(redButton);

    blueButton = new JButton("Blue Score");
    blueButton.setLocation(120, 0);
    blueButton.setSize(100, 30);
    blueButton.addActionListener(this);
    buttonPanel.add(blueButton);

    resetButton = new JButton("Reset");
    resetButton.setLocation(0, 40);
    resetButton.setSize(220, 30);
    resetButton.addActionListener(this);
    buttonPanel.add(resetButton);

    return basePanel;

   }//End Method

public void actions(ActionEvent e){

    if(e.getSource() == redButton){

        redScore ++;
        redLabel.setText("" + redScore);

    }else if(e.getSource() == blueButton){

        blueScore++;
        blueLabel.setText("" + blueScore);

    }else if(e.getSource() == resetButton){

        redScore = 0;
        blueScore = 0;
        redLabel.setText("" + redScore);
        blueLabel.setText("" + blueScore);

    }

}//End Method

}//End Class

另外，如果你能解释一下抽象类是什么，那也是有帮助的，但实际上我只需要知道如何让JButton工作......

谢谢！

Answer 1

编译器抱怨是因为你的类不是抽象的，但它没有实现一个或多个声明要实现的方法（特别是actionPerformed的方法ActionListener ）。我认为您只需要重命名actions方法：

<击>

public void actions(ActionEvent e){. . .

<击>

public void actionPerformed(ActionEvent e){. . .

Answer 2

您需要检查abstract的所有ActionListener方法是否已实施。

你缺少对void actionPerformed(ActionEvent e)

的定义

Answer 3

将此方法放入ScoreBoard类 -

@Override
public void actionPerformed(ActionEvent ae) {
     // do something
}

如果你不想让ScoreBoard类实现ActionListener，你也可以用这种方式添加监听器 -

redButton.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent ae) {
         // do something
    }
};

如果要共享侦听器，请创建其实例并将其添加到所有按钮。

要了解抽象类，请阅读此http://docs.oracle.com/javase/tutorial/java/IandI/abstract.html

如何使用非抽象类实现ActionListener？ Java的

3 个答案: