java 画带箭头的直线

       最近需要用到java带箭头的直线，在网上搜了一下，这里主要是来自网上，自己添加了箭头随鼠标的移动而改变的功能。自己还一直没有理解是怎么计算箭头的坐标的。看来高中学的几何知识都搞忘咯。不说这些了，先来看一看运行的效果。

具体代码如下：

package com.mengke.j2se.scpture;import java.awt.*;import javax.swing.*;import java.awt.event.MouseEvent;import java.awt.event.MouseListener;import java.awt.event.MouseMotionListener;import java.awt.geom.*;class ArrowLinePanel extends JPanel implements MouseMotionListener,MouseListener{// confirm the line position private int x1 = 0; private int y1 = 0; private int x2 = 0; private int y2 = 0; public ArrowLinePanel() {setBackground(Color.white);addMouseListener(this);addMouseMotionListener(this);}public void paintComponent(Graphics g) {super.paintComponent(g);Graphics2D g2 = (Graphics2D) g;g2.setPaint(Color.black);drawAL(x1, y1, x2, y2, g2);// 这里x1, y1, x2, y2必须要声明并且初始化，而具体声明的位置和初始化的值}public static void drawAL(int sx, int sy, int ex, int ey, Graphics2D g2){double H = 10; // 箭头高度double L = 4; // 底边的一半int x3 = 0;int y3 = 0;int x4 = 0;int y4 = 0;double awrad = Math.atan(L / H); // 箭头角度double arraow_len = Math.sqrt(L * L + H * H); // 箭头的长度double[] arrXY_1 = rotateVec(ex - sx, ey - sy, awrad, true, arraow_len);double[] arrXY_2 = rotateVec(ex - sx, ey - sy, -awrad, true, arraow_len);double x_3 = ex - arrXY_1[0]; // (x3,y3)是第一端点double y_3 = ey - arrXY_1[1];double x_4 = ex - arrXY_2[0]; // (x4,y4)是第二端点double y_4 = ey - arrXY_2[1];Double X3 = new Double(x_3);x3 = X3.intValue();Double Y3 = new Double(y_3);y3 = Y3.intValue();Double X4 = new Double(x_4);x4 = X4.intValue();Double Y4 = new Double(y_4);y4 = Y4.intValue();// 画线g2.drawLine(sx, sy, ex, ey);//GeneralPath triangle = new GeneralPath();triangle.moveTo(ex, ey);triangle.lineTo(x3, y3);triangle.lineTo(x4, y4);triangle.closePath();//实心箭头g2.fill(triangle);//非实心箭头//g2.draw(triangle);}// 计算public static double[] rotateVec(int px, int py, double ang,boolean isChLen, double newLen) {double mathstr[] = new double[2];// 矢量旋转函数，参数含义分别是x分量、y分量、旋转角、是否改变长度、新长度double vx = px * Math.cos(ang) - py * Math.sin(ang);double vy = px * Math.sin(ang) + py * Math.cos(ang);if (isChLen) {double d = Math.sqrt(vx * vx + vy * vy);vx = vx / d * newLen;vy = vy / d * newLen;mathstr[0] = vx;mathstr[1] = vy;}return mathstr;}@Overridepublic void mouseDragged(MouseEvent e) { //改变箭头的坐标x2 = e.getX();y2 = e.getY();repaint();}@Overridepublic void mouseMoved(MouseEvent e) {}@Overridepublic void mouseClicked(MouseEvent e) {}@Overridepublic void mouseEntered(MouseEvent e) {}@Overridepublic void mouseExited(MouseEvent e) {}@Overridepublic void mousePressed(MouseEvent e) { //设置箭头的起始坐标x1 = e.getX();y1 = e.getY();}@Overridepublic void mouseReleased(MouseEvent e) {}}

 

测试类：

package com.mengke.j2se.scpture;public class DrawFrame extends JFrame {// 活动图窗口大小public static final int DEFAULT_WIDTH = 1000;public static final int DEFAULT_HEIGHT = 800;public DrawFrame() {setTitle("Activity Diagram");setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);ArrowLinePanel panel = new ArrowLinePanel();add(panel);}public static void main(String args[]) {DrawFrame frame = new DrawFrame();frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);frame.setVisible(true);}}