java 画带箭头的直线

2023-11-10 02:03| 来源: 网络整理| 查看: 265

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; } @Override public void mouseDragged(MouseEvent e) { //改变箭头的坐标 x2 = e.getX(); y2 = e.getY(); repaint(); } @Override public void mouseMoved(MouseEvent e) { } @Override public void mouseClicked(MouseEvent e) { } @Override public void mouseEntered(MouseEvent e) { } @Override public void mouseExited(MouseEvent e) { } @Override public void mousePressed(MouseEvent e) { //设置箭头的起始坐标 x1 = e.getX(); y1 = e.getY(); } @Override public 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); } }

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