Question

所以这是我的RocketShip的面板，我想将MouseListener和我的MouseMotionListener添加到它，但它告诉我“这个”是一个无效的名称。我的教科书有时使用这个，教授也建议我们在这个例子中使用“this”，所以我不知道问题是什么。我的代码如下。感谢您提供的任何建议。

    import java.applet.*;
import java.awt.*;           
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JPanel;

//I cannot understand how to draw my new rocketship or how to update the coordinates for mouse moved, mouse dragged, mouse pressed or mouse released
//also not sure how to work with setShooting
public class RocketShipPanel extends JPanel implements MouseListener,MouseMotionListener
{
    private final int WIDTH = 300, HEIGHT = 300;
    RocketShip ship = new RocketShip();

    public RocketShipPanel(){ //constructor
        addMouseListener (this());
        addMouseMotionListener (this());

        setBackground (Color.black);
        setPreferredSize (new Dimension(WIDTH, HEIGHT));
    }


    public void paintComponent (Graphics page)
    {
        super.paintComponent(page);

        ship.draw(page, 50);


    }

    public void mousePressed (MouseEvent event)
    {
        ship.setShooting(true);
        repaint();
    }
    public void mouseReleased (MouseEvent event) 
    {
        ship.setShooting(false);
        repaint();
    }
    public void mouseMoved (MouseEvent event)
    {

        Point point1 = event.getPoint();
        int x = point1.x;
        int y = point1.y;
        ship.move(x, y);

        repaint();
    }
    public void mouseDragged (MouseEvent event)
    {

        Point point1 = event.getPoint();
        int x = point1.x;
        int y = point1.y;
        ship.move(x, y);

        //pointList.add(event.getPoint());

        repaint();
    }
    //--------------------------------------------------------------
    //  Provide empty definitions for unused event methods.
    //--------------------------------------------------------------

    public void mouseEntered (MouseEvent event) {}
    public void mouseExited (MouseEvent event) {}
    public void mouseClicked(MouseEvent event) {}


    public static void main (String[] args)
    {
        JFrame frame = new JFrame ("RocketShip");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

        frame.getContentPane().add (new RocketShipPanel());

        frame.pack();
        frame.setVisible(true);
    }
}

Answer 1

this后您不需要括号。它就像一个变量名，而不是一个方法。

Answer 2

这是JAVA中的关键字，不应将其视为方法，它是对当前对象的引用。您可以通过以下链接了解此关键字 - http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html

不知道为什么我不能得到addMouseListener（this（）），addMouseMotionListener（this（））工作

2 个答案: