在 Java 中捕获（捕获）窗口中的鼠标光标

Question

我正在寻找一种方法，在鼠标进入窗口后捕获或捕获该窗口中的鼠标，就像鼠标被捕获在虚拟机窗口中一样，直到用户按 CTRL+ALT+DEL 或以其他方式释放鼠标。我如何在 Java 中实现这一点？全屏显示不是一个选择。

编辑：

这里有一些 SSCCE 供您参考。此代码会将您的鼠标困在窗口中。要退出，您只需在生成的框架内并直接移动到关闭按钮即可。如果您注意到，当鼠标试图离开时，它会自动返回到 (0,0)。我需要知道的是如何让它返回到它退出的坐标。我尝试用 getX() 和 getY() 代替 (0,0)，但机器人不会将鼠标返回那里（我认为响应时间很慢）。我还让机器人将鼠标移回到 crosshair.x 和 crosshair.y，但是如果用户在正确的时刻单击，这（以及其他）仍然允许鼠标逃脱。有什么想法吗？

主类：

import java.awt.AWTException;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.image.BufferStrategy;
import java.awt.image.MemoryImageSource;
import java.awt.Point;
import java.awt.Robot;
import java.awt.Toolkit;
import javax.swing.JFrame;

public class Game extends JFrame implements MouseMotionListener, MouseListener{

    private int windowWidth = 640;
    private int windowHeight = 480;
        private Crosshair crosshair;

    public static void main(String[] args) {
        new Game();
    }

    public Game() {
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(windowWidth, windowHeight);
        this.setResizable(false);
        this.setLocation(0,0);
        this.setVisible(true);

        this.createBufferStrategy(2);
                addMouseMotionListener(this);
                addMouseListener(this);
        initGame();

        while(true) {
            long start = System.currentTimeMillis();
            gameLoop();
            while(System.currentTimeMillis()-start < 5) {
                            //empty while loop
            }
        }
    }

    private void initGame() {
            hideCursor();
            crosshair = new Crosshair (windowWidth/2, windowHeight/2);
    }

        private void gameLoop() {
            //game logic
            drawFrame();
        }

        private void drawFrame() {

            BufferStrategy bf = this.getBufferStrategy();
            Graphics g = (Graphics)bf.getDrawGraphics();
            try {
                g = bf.getDrawGraphics();
                Color darkBlue = new Color(0x010040);
                g.setColor(darkBlue);
                g.fillRect(0, 0, windowWidth, windowHeight);
                drawCrossHair(g);
            } finally {
                g.dispose();
            }
            bf.show();
            Toolkit.getDefaultToolkit().sync();
        }

        private void drawCrossHair(Graphics g){
            Color yellow = new Color (0xEDFF62);
            g.setColor(yellow);
            g.drawOval(crosshair.x, crosshair.y, 40, 40);

            g.fillArc(crosshair.x + 10, crosshair.y + 21 , 20, 20, -45, -90);
            g.fillArc(crosshair.x - 1, crosshair.y + 10, 20, 20, -135, -90);
            g.fillArc(crosshair.x + 10, crosshair.y - 1, 20, 20, -225, -90);
            g.fillArc(crosshair.x + 21, crosshair.y + 10, 20, 20, -315, -90);
        }

        @Override
        public void mouseDragged(MouseEvent e) {
        //empty method
        }

        @Override
        public void mouseMoved(MouseEvent e) {
        crosshair.x = e.getX();
        crosshair.y = e.getY();
        }

        private void hideCursor() {
            int[] pixels = new int[16 * 16];
            Image image = Toolkit.getDefaultToolkit().createImage(new MemoryImageSource(16, 16, pixels, 0, 16));
            Cursor transparentCursor = Toolkit.getDefaultToolkit().createCustomCursor(image, new Point(0, 0), "invisiblecursor");
            getContentPane().setCursor(transparentCursor);
    }

        public void mouseExited(MouseEvent e) {
            System.out.println("Event: " + e);
            try {
                Robot robot = new Robot();
                robot.mouseMove(0, 0);// When I use (getX(),getY()) instead of (0,0) the robot will not move the mouse at all even though getX() and getY() are the coordinates I want the mouse to be moved to.  Also the mouse can still escape, even when crosshair.x and crosshair.y are used as the coordinates.  It seems that robot is too slow.
            }
            catch (AWTException ex) {
                ex.printStackTrace();
            }
        }

        public void mouseEntered(MouseEvent e){
        }

        public void mousePressed(MouseEvent e) {
        }

        public void mouseReleased(MouseEvent e) {
        }

        public void mouseClicked(MouseEvent e) {
        }
}

另一类：

public class Crosshair{
        public int x;
    public int y;
    public Crosshair(int x, int y) {
        this.x = x;
        this.y = y;
        }
}

Answer 1

我想你可以使用 全局事件监听器 来监听鼠标输入该帧的事件。然后，在鼠标退出事件中，我想您可以使用机器人在鼠标离开框架后重置鼠标的位置。

Answer 2

好吧，我不想假装自己是游戏开发人员，但链接中提供的代码对于简单的“乒乓球游戏”来说非常糟糕（据我所知）。我复制了代码并运行它，以便球可以弹跳。

在我的计算机上，CPU 利用率为 50%，因为无限 while 循环浪费了 CPU 时间来提供球运动的动画。使用休眠 5 毫秒的线程而不是占用 CPU 5 毫秒的简单更改会导致 CPU 使用率下降到大约 18%。

然后我更改了代码以在 Swing 面板上制作球动画。代码更容易编写，CPU 使用率下降到 1%，并且球动画速度更快。

这是我的最终版本。您应该能够通过不将面板添加到框架然后再次调用 drawFrame() 方法来切换回使用缓冲策略。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.image.BufferStrategy;

import javax.swing.*;

public class Game3 extends JFrame {

    /**
     * @author Georgi Khomeriki
     */

    private Ball ball;

    // added this
    private JPanel gamePanel;

    private int windowWidth = 800;
    private int windowHeight = 600;


    public static void main(String[] args) {
        new Game3();
    }

    public Game3() {
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(windowWidth, windowHeight);
        this.setResizable(false);
        this.setLocation(100, 100);
        this.setVisible(true);

        this.createBufferStrategy(2);

        initGame3();
/*
        while(true) {
            long start = System.currentTimeMillis();
            gameLoop();
            while(System.currentTimeMillis()-start < 5) {
                 //do nothing
            }
        }
*/

        Thread thread = new Thread(new Runnable()
        {
            public void run()
            {
                while(true)
                {
                    gameLoop();
                    try { Thread.sleep(5); }
                    catch(Exception e) {}
                }
            }
        });
        thread.start();

    }

    private void initGame3() {
        // all you're game variables should be initialized here
        ball = new Ball(windowWidth/2, windowHeight/2, 5, 5);

        // added these lines

        gamePanel = new GamePanel();
        gamePanel.setBackground(Color.BLACK);
        add(gamePanel);
    }

    private void gameLoop() {
        // your game logic goes here

// move the ball
    ball.x = ball.x + ball.dx;
    ball.y = ball.y + ball.dy;

    // change the direction of the ball if it hits a wall
    if(ball.x <= 0 || ball.x >= windowWidth-40)
        ball.dx = -ball.dx;
    if(ball.y <= 0 || ball.y >= windowHeight-40)
        ball.dy = -ball.dy;


        // changed to following to use Swing instead of buffer strategy
//      drawFrame();
        gamePanel.repaint();
    }

    private void drawFrame() {
        // code for the drawing goes here
        BufferStrategy bf = this.getBufferStrategy();
        Graphics g = null;

        try {
            g = bf.getDrawGraphics();

            // clear the back buffer (just draw a big black rectangle over it)
            g.setColor(Color.BLACK);
            g.fillRect(0, 0, windowWidth, windowHeight);

drawBall(g);


        } finally {
            // It is best to dispose() a Graphics object when done with it.
            g.dispose();
        }

        // Shows the contents of the backbuffer on the screen.
        bf.show();

        //Tell the System to do the Drawing now, otherwise it can take a few extra ms until
        //Drawing is done which looks very jerky
        Toolkit.getDefaultToolkit().sync();
    }

    private void drawBall(Graphics g) {

        g.setColor(Color.GREEN);
        g.fillOval(ball.x, ball.y, 40, 40);
    }

    // added this

    class GamePanel extends JPanel
    {
        protected void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            drawBall(g);
        }
    }


    class Ball {

        public int x;
        public int y;
        public int dx;
        public int dy;

        public Ball(int x, int y, int dx, int dy) {
            this.x = x;
            this.y = y;
            this.dx = dx;
            this.dy = dy;
        }
    }



}

Answer 3

正如 camickr 提到的，您可以使用机器人来完成此操作。人们通常会建议不要这样做，但这里有一个非常好的机器人入门知识可以帮助您入门：

http://www.developer.com/java/other/article.php/2212401/Introduction-to-the-Java-Robot -Java中的类.htm