ITEEDU

2－1－2：MouseMotionListener的使用：

下面是讨论MouseMotionListener的使用时机,它提供的下面的两个方法，可让你随时掌握鼠标的坐标，并处理拖曳鼠标 的操作。

--------------------------------------------------------------------------------------------------------------
          MouseMotionListener                                  mouseDragged(MouseEvent e)
                                                               mouseMoved(MouseEvent e)
--------------------------------------------------------------------------------------------------------------

下面的范例让你知道鼠标在JFrame上的坐标，并拖曳出直线来。

例子：MouseDemo3.java

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

/*为了达到画线的功能，我们分别implements MouseListener与MouseMotionListener.
 */
public class MouseDemo3 extends JFrame implements MouseListener,
		MouseMotionListener {
	int flag;// flag=1代表Mouse Moved,flag=2代表Mouse Dragged
	int x = 0;
	int y = 0;
	int startx, starty, endx, endy;// 起始坐标与终点坐标

	public MouseDemo3() {
		Container contentPane = getContentPane();
		contentPane.addMouseListener(this);
		contentPane.addMouseMotionListener(this);
		setSize(300, 300);
		show();
		addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	}

	/* 由mousePressed(),mouseReleased()取得示拖曳的开始与结束坐标 */
	public void mousePressed(MouseEvent e) {
		startx = e.getX();
		starty = e.getY();
	}

	public void mouseReleased(MouseEvent e) {
		endx = e.getX();
		endy = e.getY();
	}

	public void mouseEntered(MouseEvent e) {
	}

	public void mouseExited(MouseEvent e) {
	}

	public void mouseClicked(MouseEvent e) {
	}

	/* mouseMoved(),mouseDragged()取得鼠标移动的每一个坐标，并调用repaint()方法 */
	public void mouseMoved(MouseEvent e) {
		flag = 1;
		x = e.getX();
		y = e.getY();
		repaint();
	}

	public void mouseDragged(MouseEvent e) {
		flag = 2;
		x = e.getX();
		y = e.getY();
		repaint();
	}

	public void update(Graphics g) {
		g.setColor(this.getBackground());
		g.fillRect(0, 0, getWidth(), getHeight());
		paint(g);
	}

	public void paint(Graphics g) {
		g.setColor(Color.black);
		if (flag == 1) {
			g.drawString("鼠标坐标：(" + x + "," + y + ")", 10, 50);
			g.drawLine(startx, starty, endx, endy);
		}
		if (flag == 2) {
			g.drawString("拖曳鼠标价坐标：(" + x + "," + y + ")", 10, 50);
			g.drawLine(startx, starty, x, y);
		}
	}

	public static void main(String[] args) {
		new MouseDemo3();
	}
}