根据角度在圆周围画一条线
Draw A line around the circle based on angle
我希望它看起来像什么：
圆圈随着箭头围绕中心圆移动。
目前的情况：
我想在两个圆之间画两条线。然而，这些圆圈在屏幕上四处移动，我不知道如何在它们之间画线。例如，我总是在两个圆圈的左上角之间画一条线，但仅此而已。我需要帮助在 java 中绘制一条线，该线将根据其位置进行调整，以便随着圆圈的移动使线围绕边缘移动
for (int z = 0; z < lines.size(); z++) {
if (lines.get(z).getfState().equals(states.get(a).getText()) && !lines.get(z).getfState().equals(lines.get(z).getnState())) {
transition.get(z).setIcon(null);
for (int x = 0; x < states.size(); x++) {
if (states.get(x).getText().equals(lines.get(z).getnState()) && states.get(a).getText().equals(lines.get(z).getfState())) {
int xbegin = (int) states.get(a).getBounds().getX();
int ybegin = (int) states.get(a).getBounds().getY();
int xend = (int) states.get(x).getBounds().getX();
int yend = (int) states.get(x).getBounds().getY();
if (xbegin > xend) {
Path2D.Double rect = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend + 30, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect.getBounds().x, rect.getBounds().y, rect.getBounds().width + 20, rect.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
} else {
if (xend - xbegin < 75) {
xbegin = xbegin - 20;
xend = xend - 20;
}
xbegin = xbegin + 5;
ybegin = ybegin + 25;
xend = xend + 5;
yend = yend + 25;
Path2D.Double rect = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect.getBounds().x, rect.getBounds().y, rect.getBounds().width + 20, rect.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
}
}
}
} else if (lines.get(z).getnState().equals(states.get(a).getText()) && !lines.get(z).getfState().equals(lines.get(z).getnState())) {
transition.get(z).setIcon(null);
for (int x = 0; x < states.size(); x++) {
if (states.get(x).getText().equals(lines.get(z).getfState()) && states.get(a).getText().equals(lines.get(z).getnState())) {
int xend = (int) states.get(a).getBounds().getX();
int yend = (int) states.get(a).getBounds().getY();
int xbegin = (int) states.get(x).getBounds().getX();
int ybegin = (int) states.get(x).getBounds().getY();
if (xbegin > xend) {
Path2D.Double rect2 = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend + 30, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect2.getBounds().x, rect2.getBounds().y, rect2.getBounds().width + 20, rect2.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
} else {
if (xend - xbegin < 75) {
xbegin = xbegin + 20;
xend = xend + 20;
}
xbegin = xbegin + 5;
ybegin = ybegin + 25;
xend = xend + 5;
yend = yend + 25;
Path2D.Double rect2 = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect2.getBounds().x, rect2.getBounds().y, rect2.getBounds().width + 20, rect2.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
}
}
}
public static Path2D.Double createArrowForLine(
int fromPointx,
int fromPointy,
double rotationDeg,
double length,
double wingsAngleDeg) {
double ax = fromPointx;
double ay = fromPointy;
double radB = Math.toRadians(-rotationDeg + wingsAngleDeg);
double radC = Math.toRadians(-rotationDeg - wingsAngleDeg);
Path2D resultPath = new Path2D.Double();
resultPath.moveTo(length * Math.cos(radB) + ax, length * Math.sin(radB) + ay);
resultPath.lineTo(ax, ay);
resultPath.lineTo(length * Math.cos(radC) + ax, length * Math.sin(radC) + ay);
return (Path2D.Double) resultPath;
}
虽然问题中出现了一些问题，而且目前提供的代码看起来有问题，但现在的问题核心非常有趣...
解决这个问题有不同的选择。从您目前提供的图像来看，圆圈似乎始终具有相同的大小，这使事情变得简单得多。对于不同大小的圆，你真的必须计算圆的 切线 在所需的方向上，同时考虑另一个圆的半径。当然，这是可能的，但有点不那么琐碎。
如果你有同样大小的圆圈，你可以
- 计算两个圆心的差值
- 将其除以距离，得到（标准化的）方向
- 将这个方向旋转90°
- 按半径缩放旋转方向矢量
- 将缩放和旋转后的矢量添加到圆心
这将产生这样一条直线的一个端点。可以顺时针旋转一次，逆时针旋转一次约90°，分别得到直线的"upper"和"lower"端点。
图像已通过编辑更新，见下文
实际的计算是在下面MCVE的computeLine方法中完成的。请注意，此示例使用 "simple" 方法， 尽管 它使用的圆圈大小略有不同。效果是，当两个圆的大小差异太大时（基本上与圆之间的距离相比），那么线可能会稍微 与圆相交 。但解决方案应该是简单性和普遍适用性之间的合理权衡。特别是，对于同样大小的圆，根本不会有交集。
代码已通过编辑更新，见下文
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Path2D;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class LinesAtCirclesTest
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
@Override
public void run()
{
createAndShowGUI();
}
});
}
private static void createAndShowGUI()
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel linesAtCirclesTestPanel = new LinesAtCirclesTestPanel();
f.getContentPane().add(linesAtCirclesTestPanel);
f.setSize(400,400);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}
class LinesAtCirclesTestPanel extends JPanel
implements MouseListener, MouseMotionListener
{
private Point2D draggedCenter;
private List<Point2D> centers = new ArrayList<Point2D>();
private List<Double> radii = new ArrayList<Double>();
public LinesAtCirclesTestPanel()
{
addMouseListener(this);
addMouseMotionListener(this);
addCircle(100, 100, 30);
addCircle(200, 300, 50);
addCircle(300, 200, 40);
}
private void addCircle(double x, double y, double radius)
{
centers.add(new Point2D.Double(x,y));
radii.add(radius);
}
@Override
protected void paintComponent(Graphics gr)
{
super.paintComponent(gr);
Graphics2D g = (Graphics2D)gr;
g.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
for (int i=0; i<centers.size(); i++)
{
Point2D center0 = centers.get(i);
double radius0 = radii.get(i);
Shape ellipse = new Ellipse2D.Double(
center0.getX() - radius0, center0.getY() - radius0,
radius0 + radius0, radius0 + radius0);
g.setColor(Color.LIGHT_GRAY);
g.fill(ellipse);
g.setColor(Color.BLACK);
g.draw(ellipse);
}
g.setColor(Color.RED);
for (int i=0; i<centers.size() - 1; i++)
{
Point2D center0 = centers.get(i);
double radius0 = radii.get(i);
Point2D center1 = centers.get(i+1);
double radius1 = radii.get(i+1);
g.draw(createArrow(computeLine(center0, radius0, center1, radius1, true)));
g.draw(createArrow(computeLine(center0, radius0, center1, radius1, false)));
}
}
private static Shape createArrow(Line2D line)
{
double dx = line.getX2() - line.getX1();
double dy = line.getY2() - line.getY1();
double angleToX = Math.atan2(dy, dx);
final double angleRad = Math.toRadians(30);
final double headLength = 20.0f;
double dxL = Math.cos(Math.PI + angleToX + angleRad) * headLength;
double dyL = Math.sin(Math.PI + angleToX + angleRad) * headLength;
double dxR = Math.cos(Math.PI + angleToX - angleRad) * headLength;
double dyR = Math.sin(Math.PI + angleToX - angleRad) * headLength;
Path2D arrow = new Path2D.Double();
arrow.moveTo(line.getX1(), line.getY1());
arrow.lineTo(line.getX2(), line.getY2());
arrow.lineTo(line.getX2() + dxL, line.getY2() + dyL);
arrow.moveTo(line.getX2(), line.getY2());
arrow.lineTo(line.getX2() + dxR, line.getY2() + dyR);
return arrow;
}
private static Line2D computeLine(
Point2D center0, double radius0,
Point2D center1, double radius1,
boolean upper)
{
double dx = center1.getX() - center0.getX();
double dy = center1.getY() - center0.getY();
double invLength = 1.0 / Math.hypot(dx, dy);
double dirX = dx * invLength;
double dirY = dy * invLength;
double rotDirX = dirY;
double rotDirY = -dirX;
if (upper)
{
rotDirX = -dirY;
rotDirY = dirX;
}
double x0 = center0.getX() + rotDirX * radius0;
double y0 = center0.getY() + rotDirY * radius0;
double x1 = center1.getX() + rotDirX * radius1;
double y1 = center1.getY() + rotDirY * radius1;
if (upper)
{
return new Line2D.Double(x1, y1, x0, y0);
}
return new Line2D.Double(x0, y0, x1, y1);
}
@Override
public void mousePressed(MouseEvent e)
{
draggedCenter = null;
for (int i=0; i<centers.size(); i++)
{
Point2D center = centers.get(i);
double radius = radii.get(i);
if (e.getPoint().distance(center) < radius)
{
draggedCenter = center;
}
}
}
@Override
public void mouseReleased(MouseEvent e)
{
draggedCenter = null;
}
@Override
public void mouseDragged(MouseEvent e)
{
if (draggedCenter == null)
{
return;
}
draggedCenter.setLocation(e.getPoint());
repaint();
}
@Override
public void mouseMoved(MouseEvent e)
{
// Not used
}
@Override
public void mouseClicked(MouseEvent e)
{
// Not used
}
@Override
public void mouseEntered(MouseEvent e)
{
// Not used
}
@Override
public void mouseExited(MouseEvent e)
{
// Not used
}
}
EDIT in response to the comment:
原始代码计算了 Line2D 个对象。从一条线创建一个箭头，在最简单的情况下，基本上是用一点三角学来完成的，网络上有很多这方面的资源。
为了回应评论，我扩展了示例以显示简单的箭头，如上图所示。
然而，当仔细观察时，可能会注意到这种箭头有几个自由度：
- 头部长度应该是绝对长度还是相对于箭头？
- 头部宽度应该是绝对的还是相对于箭头的？
- (或者：箭头的角度应该是多少？)
- 箭头是填充还是由线条组成？
- 箭头的"trunk"应该是单线，还是轮廓形状？
- 后备箱的宽度应该是多少？
- ...
为了涵盖其中的一些自由度，我创建了一个 ArrowCreator class a while ago, and there's also a sample 展示如何使用它。
我希望它看起来像什么：
圆圈随着箭头围绕中心圆移动。
目前的情况：
我想在两个圆之间画两条线。然而，这些圆圈在屏幕上四处移动，我不知道如何在它们之间画线。例如，我总是在两个圆圈的左上角之间画一条线，但仅此而已。我需要帮助在 java 中绘制一条线，该线将根据其位置进行调整，以便随着圆圈的移动使线围绕边缘移动
for (int z = 0; z < lines.size(); z++) {
if (lines.get(z).getfState().equals(states.get(a).getText()) && !lines.get(z).getfState().equals(lines.get(z).getnState())) {
transition.get(z).setIcon(null);
for (int x = 0; x < states.size(); x++) {
if (states.get(x).getText().equals(lines.get(z).getnState()) && states.get(a).getText().equals(lines.get(z).getfState())) {
int xbegin = (int) states.get(a).getBounds().getX();
int ybegin = (int) states.get(a).getBounds().getY();
int xend = (int) states.get(x).getBounds().getX();
int yend = (int) states.get(x).getBounds().getY();
if (xbegin > xend) {
Path2D.Double rect = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend + 30, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect.getBounds().x, rect.getBounds().y, rect.getBounds().width + 20, rect.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
} else {
if (xend - xbegin < 75) {
xbegin = xbegin - 20;
xend = xend - 20;
}
xbegin = xbegin + 5;
ybegin = ybegin + 25;
xend = xend + 5;
yend = yend + 25;
Path2D.Double rect = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect.getBounds().x, rect.getBounds().y, rect.getBounds().width + 20, rect.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
}
}
}
} else if (lines.get(z).getnState().equals(states.get(a).getText()) && !lines.get(z).getfState().equals(lines.get(z).getnState())) {
transition.get(z).setIcon(null);
for (int x = 0; x < states.size(); x++) {
if (states.get(x).getText().equals(lines.get(z).getfState()) && states.get(a).getText().equals(lines.get(z).getnState())) {
int xend = (int) states.get(a).getBounds().getX();
int yend = (int) states.get(a).getBounds().getY();
int xbegin = (int) states.get(x).getBounds().getX();
int ybegin = (int) states.get(x).getBounds().getY();
if (xbegin > xend) {
Path2D.Double rect2 = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend + 30, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect2.getBounds().x, rect2.getBounds().y, rect2.getBounds().width + 20, rect2.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
} else {
if (xend - xbegin < 75) {
xbegin = xbegin + 20;
xend = xend + 20;
}
xbegin = xbegin + 5;
ybegin = ybegin + 25;
xend = xend + 5;
yend = yend + 25;
Path2D.Double rect2 = new Path2D.Double(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7));
OutlineIcon transit = new OutlineIcon(drawArrowLine(xbegin, ybegin, xend - 10, yend, 10, 7), Color.BLACK);
transition.get(z).setIcon(transit);
transition.get(z).setBounds(rect2.getBounds().x, rect2.getBounds().y, rect2.getBounds().width + 20, rect2.getBounds().height + 20);
jPanel2.revalidate();
jPanel2.repaint();
}
}
}
public static Path2D.Double createArrowForLine(
int fromPointx,
int fromPointy,
double rotationDeg,
double length,
double wingsAngleDeg) {
double ax = fromPointx;
double ay = fromPointy;
double radB = Math.toRadians(-rotationDeg + wingsAngleDeg);
double radC = Math.toRadians(-rotationDeg - wingsAngleDeg);
Path2D resultPath = new Path2D.Double();
resultPath.moveTo(length * Math.cos(radB) + ax, length * Math.sin(radB) + ay);
resultPath.lineTo(ax, ay);
resultPath.lineTo(length * Math.cos(radC) + ax, length * Math.sin(radC) + ay);
return (Path2D.Double) resultPath;
}
虽然问题中出现了一些问题，而且目前提供的代码看起来有问题，但现在的问题核心非常有趣...
解决这个问题有不同的选择。从您目前提供的图像来看，圆圈似乎始终具有相同的大小，这使事情变得简单得多。对于不同大小的圆，你真的必须计算圆的 切线 在所需的方向上，同时考虑另一个圆的半径。当然，这是可能的，但有点不那么琐碎。
如果你有同样大小的圆圈，你可以
- 计算两个圆心的差值
- 将其除以距离，得到（标准化的）方向
- 将这个方向旋转90°
- 按半径缩放旋转方向矢量
- 将缩放和旋转后的矢量添加到圆心
这将产生这样一条直线的一个端点。可以顺时针旋转一次，逆时针旋转一次约90°，分别得到直线的"upper"和"lower"端点。
图像已通过编辑更新，见下文
实际的计算是在下面MCVE的computeLine方法中完成的。请注意，此示例使用 "simple" 方法， 尽管 它使用的圆圈大小略有不同。效果是，当两个圆的大小差异太大时（基本上与圆之间的距离相比），那么线可能会稍微 与圆相交 。但解决方案应该是简单性和普遍适用性之间的合理权衡。特别是，对于同样大小的圆，根本不会有交集。
代码已通过编辑更新，见下文
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Path2D;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class LinesAtCirclesTest
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
@Override
public void run()
{
createAndShowGUI();
}
});
}
private static void createAndShowGUI()
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel linesAtCirclesTestPanel = new LinesAtCirclesTestPanel();
f.getContentPane().add(linesAtCirclesTestPanel);
f.setSize(400,400);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}
class LinesAtCirclesTestPanel extends JPanel
implements MouseListener, MouseMotionListener
{
private Point2D draggedCenter;
private List<Point2D> centers = new ArrayList<Point2D>();
private List<Double> radii = new ArrayList<Double>();
public LinesAtCirclesTestPanel()
{
addMouseListener(this);
addMouseMotionListener(this);
addCircle(100, 100, 30);
addCircle(200, 300, 50);
addCircle(300, 200, 40);
}
private void addCircle(double x, double y, double radius)
{
centers.add(new Point2D.Double(x,y));
radii.add(radius);
}
@Override
protected void paintComponent(Graphics gr)
{
super.paintComponent(gr);
Graphics2D g = (Graphics2D)gr;
g.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
for (int i=0; i<centers.size(); i++)
{
Point2D center0 = centers.get(i);
double radius0 = radii.get(i);
Shape ellipse = new Ellipse2D.Double(
center0.getX() - radius0, center0.getY() - radius0,
radius0 + radius0, radius0 + radius0);
g.setColor(Color.LIGHT_GRAY);
g.fill(ellipse);
g.setColor(Color.BLACK);
g.draw(ellipse);
}
g.setColor(Color.RED);
for (int i=0; i<centers.size() - 1; i++)
{
Point2D center0 = centers.get(i);
double radius0 = radii.get(i);
Point2D center1 = centers.get(i+1);
double radius1 = radii.get(i+1);
g.draw(createArrow(computeLine(center0, radius0, center1, radius1, true)));
g.draw(createArrow(computeLine(center0, radius0, center1, radius1, false)));
}
}
private static Shape createArrow(Line2D line)
{
double dx = line.getX2() - line.getX1();
double dy = line.getY2() - line.getY1();
double angleToX = Math.atan2(dy, dx);
final double angleRad = Math.toRadians(30);
final double headLength = 20.0f;
double dxL = Math.cos(Math.PI + angleToX + angleRad) * headLength;
double dyL = Math.sin(Math.PI + angleToX + angleRad) * headLength;
double dxR = Math.cos(Math.PI + angleToX - angleRad) * headLength;
double dyR = Math.sin(Math.PI + angleToX - angleRad) * headLength;
Path2D arrow = new Path2D.Double();
arrow.moveTo(line.getX1(), line.getY1());
arrow.lineTo(line.getX2(), line.getY2());
arrow.lineTo(line.getX2() + dxL, line.getY2() + dyL);
arrow.moveTo(line.getX2(), line.getY2());
arrow.lineTo(line.getX2() + dxR, line.getY2() + dyR);
return arrow;
}
private static Line2D computeLine(
Point2D center0, double radius0,
Point2D center1, double radius1,
boolean upper)
{
double dx = center1.getX() - center0.getX();
double dy = center1.getY() - center0.getY();
double invLength = 1.0 / Math.hypot(dx, dy);
double dirX = dx * invLength;
double dirY = dy * invLength;
double rotDirX = dirY;
double rotDirY = -dirX;
if (upper)
{
rotDirX = -dirY;
rotDirY = dirX;
}
double x0 = center0.getX() + rotDirX * radius0;
double y0 = center0.getY() + rotDirY * radius0;
double x1 = center1.getX() + rotDirX * radius1;
double y1 = center1.getY() + rotDirY * radius1;
if (upper)
{
return new Line2D.Double(x1, y1, x0, y0);
}
return new Line2D.Double(x0, y0, x1, y1);
}
@Override
public void mousePressed(MouseEvent e)
{
draggedCenter = null;
for (int i=0; i<centers.size(); i++)
{
Point2D center = centers.get(i);
double radius = radii.get(i);
if (e.getPoint().distance(center) < radius)
{
draggedCenter = center;
}
}
}
@Override
public void mouseReleased(MouseEvent e)
{
draggedCenter = null;
}
@Override
public void mouseDragged(MouseEvent e)
{
if (draggedCenter == null)
{
return;
}
draggedCenter.setLocation(e.getPoint());
repaint();
}
@Override
public void mouseMoved(MouseEvent e)
{
// Not used
}
@Override
public void mouseClicked(MouseEvent e)
{
// Not used
}
@Override
public void mouseEntered(MouseEvent e)
{
// Not used
}
@Override
public void mouseExited(MouseEvent e)
{
// Not used
}
}
EDIT in response to the comment:
原始代码计算了 Line2D 个对象。从一条线创建一个箭头，在最简单的情况下，基本上是用一点三角学来完成的，网络上有很多这方面的资源。
为了回应评论，我扩展了示例以显示简单的箭头，如上图所示。
然而，当仔细观察时，可能会注意到这种箭头有几个自由度：
- 头部长度应该是绝对长度还是相对于箭头？
- 头部宽度应该是绝对的还是相对于箭头的？
- (或者：箭头的角度应该是多少？)
- 箭头是填充还是由线条组成？
- 箭头的"trunk"应该是单线，还是轮廓形状？
- 后备箱的宽度应该是多少？
- ...
为了涵盖其中的一些自由度，我创建了一个 ArrowCreator class a while ago, and there's also a sample 展示如何使用它。