java - 我无法纠正的鼠标事件未知错误

Question

我正在学习 java，在做 MouseListener 问题时，我在类声明中遇到错误，尝试了我所知道的一切，请帮助我。根据我的说法，我已经正确完成了所有编码，也将代码粘贴到了 IDE 中，但出现了同样的错误。

谢谢

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

       public class Sub extends JFrame      
    {
private JPanel mousepanel;
private JLabel statusbar;

public Sub()
{
    super("Mouse Events");
    // we didnt have a FlowLayout as we had in previous programs

    mousepanel = new JPanel();
    mousepanel.setBackground(Color.WHITE);
    add(mousepanel, BorderLayout.CENTER); //BorderLayout used instead of FlowLayout and it will place it in the center of the window.

    statusbar = new JLabel("Default");
    add(statusbar, BorderLayout.SOUTH); // same as above

    thehandler handler = new thehandler();
    mousepanel.addMouseListener(handler);
    mousepanel.addMouseMotionListener(handler);

            private class thehandler implements MouseListener, MouseMotionListener
    {
        public void mouseClicked(MouseEvent event)
        {
            statusbar.setText(String.format("Clicked at %d, %d", event.getX(), event.getY()));
        }
        public void mousePressed(MouseEvent event)
        {
            statusbar.setText("You press down the mouse.");
        }
        public void mouseReleased(MouseEvent event)
        {
            statusbar.setText("You released the mouse.");
        }
        public void mouseEntered(MouseEvent event)
        {
            statusbar.setText("You enetered the mouse panel area.");
            mousepanel.setBackground(Color.PINK);
        }
        public void mouseExited(MouseEvent event)
        {
            statusbar.setText("The mouse has left the window.");
            mousepanel.setBackground(Color.WHITE);
        }

        //these aremouse motion events

        public void mouseDragged(MouseEvent event)
        {
            statusbar.setText("Your are dragging the mouse.");
        }
        public void mouseMoved(MouseEvent event)
        {
            statusbar.setText("You moded the mouse.");
        }
    }
}
  }

Answer 1

您需要将thehandler类定义移出Sub构造函数的范围。

旁注：类名以大写字母开头。

Answer 2

将您的类定义移到构造函数之外，如下所示：

public Sub() {
    // ... rest of code
}

// ... rest of code

private class thehandler implements MouseListener, MouseMotionListener {
    // ... rest of code
}

Answer 3

检查您的大括号并使用一些 IDE，它将帮助您更轻松地纠正错误。