Java中如何监听鼠标事件

2024-07-13 00:33| 来源: 网络整理| 查看: 265

当点击鼠标按钮时，有三个监听器方法可以调用：①鼠标按下时调用mousePressed；②鼠标被释放时调用mouseReleased；③关注鼠标的最终点击事件时调用mouseClicked。鼠标点击可以由mouseClicked过程报告，该方法是MouseListener接口的一部分。通常大部分应用程序只对鼠标点击事件感兴趣，而对鼠标移动及拖动并不感兴趣，但是鼠标移动及拖动事件又经常发生，因此，鼠标移动与拖动事件定义在一个MouseMotionListener接口中。

因为MouseListener接口中有很多方法，而其中很多并不一定是我们需要的，但是我们在实现该接口的类时又必须实现MouseListener接口中所有的方法。庆幸的是，MouseAdapter类实现了MouseListener接口中的所有方法（就是空方法，并没有编写方法的具体执行过程），我们可以直接继承该类并重写我们需要的方法就可以了。下面的示例程序通过分别定义两个类MouseHandler和MouseMotionHandler演示了鼠标的点击监听、鼠标移动和拖动事件监听：

import java.awt.Cursor; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.awt.event.MouseMotionListener; import java.awt.geom.Point2D; import java.awt.geom.Rectangle2D; import java.util.ArrayList; import javax.swing.JComponent; import javax.swing.JFrame; public class MouseDemo { public static void main(String[] args){ EventQueue.invokeLater(() -> { JFrame frame = new MouseFrame(); frame.setTitle("MouseTest"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); }); } } class MouseFrame extends JFrame{ public MouseFrame(){ add(new MouseComponent()); pack(); } } class MouseComponent extends JComponent{ private static final int DEFAULT_WIDTH = 300; private static final int DEFAULT_HEIGHT = 200; private static final int SIDELENGTH = 10; private ArrayList squares; private Rectangle2D current; // the square containing the mouse cursor public MouseComponent(){ squares = new ArrayList(); current = null; addMouseListener(new MouseHandler()); addMouseMotionListener(new MouseMotionHandler()); } public Dimension getPreferredSize() { return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT); } public void paintComponent(Graphics g){ Graphics2D g2 = (Graphics2D) g; for (Rectangle2D r : squares) g2.draw(r); } public Rectangle2D find(Point2D p){ for (Rectangle2D r : squares){ if (r.contains(p)) return r; } return null; } public void add(Point2D p){ double x = p.getX(); double y = p.getY(); current = new Rectangle2D.Double(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH, SIDELENGTH); squares.add(current); repaint(); } public void remove(Rectangle2D s){ if (s == null) return; if (s == current) current = null; squares.remove(s); repaint(); } private class MouseHandler extends MouseAdapter{ public void mousePressed(MouseEvent event){ //鼠标按下时调用 current = find(event.getPoint()); if (current == null) add(event.getPoint()); } public void mouseClicked(MouseEvent event){ //鼠标点击时调用，点击两次则移除矩形 current = find(event.getPoint()); if (current != null && event.getClickCount() >= 2) remove(current); } } private class MouseMotionHandler implements MouseMotionListener{ public void mouseMoved(MouseEvent event){ //鼠标移动时调用 if (find(event.getPoint()) == null) setCursor(Cursor.getDefaultCursor()); else setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR)); } public void mouseDragged(MouseEvent event){ //鼠标按住拖动时调用 if (current != null){ int x = event.getX(); int y = event.getY(); current.setFrame(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH, SIDELENGTH); repaint(); } } } }

【本文地址】

公司简介

联系我们