mouseEntered()和mouseMoved()之间的混淆

Question

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
public class MouseEvents extends Applet implements MouseListener, MouseMotionListener
{
    String msg = "";                        // I am not implementing those methods which
    int mouseX = 0, mouseY = 0;             // are not related to my question
    public void init()
    {
        addMouseListener(this);
        addMouseMotionListener(this);
    }
    public void mouseEntered(MouseEvent me)
    {
        mouseX = 0;
        mouseY = 10;
        msg = "Mouse Entered";
        repaint();
    }
    public void mouseMoved(MouseEvent me)
    {
        mouseX = me.getX();
        mouseY = me.getY();
        showStatus("Moving mouse at "+mouseX+", "+mouseY);
    }
    public void paint(Graphics g)
    {
        g.drawString(msg, mouseX, mouseY);
    }
}

我的小程序窗口的坐标：

左上角-(0，0(
左下角-(0199(
右上角-(349，0(
右下角-(349199(

我的期望：

1. 当鼠标进入小程序窗口时，应在坐标(0, 10) 处显示消息"Mouse Entered"

2. 当鼠标移动时，状态窗口中应显示一条消息"Moving mouse at mouseX, mouseY"。其中mouseX和mouseY是鼠标的当前坐标

实际发生的情况：

消息"Mouse entered"没有显示在坐标(0, 10)处，而是显示在鼠标进入小程序窗口***的初始坐标处

例如，鼠标从Lower left corner和Lower right corner之间进入小程序窗口，例如(187, 199)，则消息"Mouse Entered"不是在(0, 10)显示，而是在(187, 199) 显示

我的问题

尽管在mouseEntered()中指定了mouseX = 0和mouseY = 10，为什么消息"Mouse Entered"显示在鼠标进入小程序窗口的坐标处，而不是显示在坐标(0, 10)处？

Answer 1

当您将鼠标移到查看窗格上时，查看窗格经常会被重新绘制。

您在此处覆盖mouseX和mouseY的值：

public void mouseMoved(MouseEvent me)
{
    mouseX = me.getX();
    mouseY = me.getY();
    showStatus("Moving mouse at "+mouseX+", "+mouseY);
}

这会导致在移动鼠标时在这些坐标处进行重绘。如果您希望mouseEntered不移动，可以使用本地变量，例如

public void mouseMoved(MouseEvent me)
{
    int currentMouseX = me.getX();
    int currentMouseY = me.getY();
    showStatus("Moving mouse at "+currentMouseX+", "+currentMouseY);
}

Answer 2

public void mouseMoved(MouseEvent me)
{
    mouseX = me.getX();
    mouseY = me.getY();
    showStatus("Moving mouse at "+mouseX+", "+mouseY);
}

每当您移动鼠标时，mouseMoved部分中的代码都会更新。因此，它显示mouseX和mouseY不是(0,10(的原因是因为您在mouseMoved方法中更改了mouseX的值和mouseY的值。使其显示鼠标最后位置的坐标。尝试创建一个不同的变量来跟踪鼠标的位置。