Java：ActionListener错误

Question

我有这个代码使用一个文本字段，程序从该文本字段接收用户的输入，所以我试图将ActionListener添加到我的文本字段输入。但是，当我编译时，我收到此错误： Quiz.java:5: error: Quiz is not abstract and does not override abstract method actionPerformed(ActionEvent) in ActionListener public class Quiz implements ActionListener {

代码：

public class Quiz implements ActionListener {

private static Label lblInput;         
private static TextField tfInput;  
private static String cityIn;       

   public void europe() {
      JFrame frame = new JFrame();      
      frame.setLayout(null);

      lblInput = new Label("Skriv in huvudstaden i : "); // Construct Label
      lblInput.setBounds(40,30,300,40);
      frame.add(lblInput);

      tfInput = new TextField(10);
      tfInput.setBounds(40,70,300,40);
      frame.add(tfInput);

      tfInput.addActionListener(this);

      frame.setTitle("Europa"); 
      frame.setSize(375, 150);
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);

   }


}

Answer 1

您必须覆盖actionPerformed(ActionEvent e)方法：

public class Quiz implements ActionListener {

    private static Label lblInput;
    private static TextField tfInput;
    private static String cityIn;

    public void europe() {
        ....
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // Your code
    }
}

编辑： （第二种方式）

您可以使用自定义ActionListener处理文本字段中的事件：

public class Quiz implements ActionListener {

    private static Label lblInput;
    private static TextField tfInput;
    private static String cityIn;

    public void europe() {
        ....
        tfInput.addActionListener(new CustomActionListener());
        ...
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // Your code
    }
}

class CustomActionListener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
        // Your code
    }
}