Question

我希望它看起来像：

https://stackoverflow.com/a/25058091/1393766

圆圈沿着中心圆圈的箭头移动。

目前的情况如何：

我想在两个圆圈之间绘制2条线。然而，这些圆圈在屏幕周围移动，我不知道有条不紊地在它们之间画线。例如，我总是有两个圆圈的左上角我想画一条线但是就是这样。我需要帮助在java中绘制一条线，它将根据其位置进行调整，以便在圆圈移动时线条围绕边缘移动

      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;
}

Answer 1

_{虽然问题中有一些小问题，而且到目前为止提供的代码看起来有问题，但现在问题的核心是非常有趣的......}

解决这个问题有不同的选择。从您目前提供的图像来看，它们看起来总是具有相同的大小，这使得事情变得更加简单。对于具有不同大小的圆，您必须在所需方向上计算圆的切线，相互考虑另一个圆的半径。当然，这是可能的，但有点不那么重要。

如果你有同样大小的圈子，你可以

计算两个圆心的差异
除以距离，以获得（标准化的）方向
将此方向旋转90°
将旋转的方向矢量按半径
将缩放和旋转的矢量添加到圆心

这将产生这样一条线的一个端点。大约90°的旋转可以在顺时针方向上进行一次，在逆时针方向上进行一次，以分别获得该线的“上”和“下”端点。

^{图像已使用EDIT更新，请参阅下文}

实际计算是在以下MCVE的computeLine方法中完成的。请注意，此示例使用“简单”方法，虽然它使用的是大小略有不同的圆圈。效果是，当两个圆的大小之间的差异太大时（基本上与圆之间的距离相比），那么这些线可能与圆相交。但解决方案应该是简单性和普遍适用性之间的合理权衡。特别是对于大小相等的圆圈，根本就没有交叉点。

^{使用EDIT更新了代码，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 } }

编辑回应评论：

原始代码计算Line2D个对象。在最简单的情况下，从一条线创建箭头基本上是通过一些三角函数完成的，并且在Web上存在许多资源。

在回应评论时，我将示例扩展为显示简单的箭头，如上图所示。

然而，当仔细研究这个时，可能会注意到这样一个箭头的几个自由度：

头部长度应该是绝对的还是相对于箭头？

头部宽度应该是绝对的还是相对于箭头？

（或者：箭头的角度应该是多少？）

箭头应该填充还是由线组成？

箭头的“主干”应该是单线还是轮廓形状？

行李箱的宽度应该是多少？

...

为了涵盖其中一些自由度，我前段时间创建了一个ArrowCreator课程，并且还有一个sample显示了如何使用它。

根据角度在圆周上绘制一条线

1 个答案: