java - 构造函数中的 Action 监听器

Question

我正在尝试创建 NewCard 类，并实现一个框架。如何将 Actionlistener 添加到 NewCard 类构造函数中的元素？我无法将 Actionlistener 放入构造函数中，当我将其放在外面时，元素“field”对于 saveButtonListener block 是不可见的。

第二个问题:try block 中的类Record抛出两个异常，为什么try block 会产生错误？

package Interface;

import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.awt.event.*;
import Engine.*;

class NewCard extends JFrame
{         
    NewCard()
    {
        JFrame Card = new JFrame(); 
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        setTitle("New Card");
        setSize(340, 580);  
        setVisible(true);
        Container contentPane = getContentPane();
        contentPane.setLayout(null);

        // Field

        JTextField field = new JTextField();
        contentPane.add(field);
        field.setBounds(110,15,200,25);

        // Button:

        JButton saveButton = new JButton("Save");
        powZawartosci.add(saveButton);
        saveButton.setBounds(95,495,150,25);

        saveButtonListener listener1 = new saveButtonListener();
        saveButton.addActionListener(listener1);
    }

    private class saveButtonListener implements ActionListener 
    {
        try
        {
            @Override
            public void actionPerformed(ActionEvent event) 
            {
                new Record(field.getText());
            }
        }
        catch(IOException e)
        {
            System.out.println("IOException");
        }
        catch(SQLException e)
        {
            System.out.println("SQLException");
        }
        finally
        {

        }
    }
}

Answer 1

您可以将操作监听器放入构造函数中，如下所示:

final JTextField field = new JTextField();
...
saveButton.addActionListener(new ActionListener() {
   @Override
   public void actionPerformed(ActionEvent event) {
      new Record(field.getText());
   }

});