Question

所以我有点想要掌握听众和诸如此类的概念在我的代码中我得到错误：

The type eventHandle.ButtonListener must implement the inherited abstract method ActionListener.actionPerformed(ActionEvent)

为什么会这样？

package test;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class eventHandle extends JApplet{
    private JButton onebutton;
    private JButton twobutton;
    private JLabel label; 
    private int flax;
    private JPanel panel;

    public void init(){
        flax = 0;
        onebutton = new JButton("click to add 1");
        onebutton.addActionListener(new ButtonListener());
        twobutton = new JButton("click to add 2");
        twobutton.addActionListener(new ButtonListener());
        label = new JLabel("count: " + flax);

        panel = new JPanel();
        panel.setLayout(new GridLayout(1,2));
        panel.add(onebutton);
        panel.add(twobutton);

        Container contain = getContentPane();
        contain.setLayout(new GridLayout(2,1));
        contain.add(label);
        contain.add(panel);

        setSize(400,300);

    }
    public class ButtonListener implements ActionListener{

        public void actionPerformed(Action event){
            if (event == onebutton){
                flax += 1;
            }
            if (event == twobutton){
                flax += 2;
            }
            label.setText("count: " + flax);
        }

    }
}

Answer 1

你没有完全覆盖ActionListener接口，你必须这样做

public void actionPerformed(ActionEvent event){

而不是

public void actionPerformed(Action event){

Answer 2

使用ActionEvent代替Action并比较JButton对象使用event.getSource()。

public void actionPerformed(ActionEvent event){
   if (event.getSource() == onebutton){
      flax += 1;
   }
   if (event.getSource() == twobutton){
     flax += 2;
   }
   label.setText("count: " + flax);
}

更多https://docs.oracle.com/javase/tutorial/uiswing/events/actionlistener.html

为什么ButtonListener没有工作？

2 个答案: