我想做一条有向线并使其移动。我可以画一条有方向的线并移动线，但是在移动线时箭头会移位
这是我的绘画方法
Line2D.Double line = new Line2D.Double(startX, startY, endX, endY);
g2d.draw(line);
tx.setToIdentity();
double angle = Math.atan2(line.y2 - line.y1, line.x2 - line.x1);
tx.translate(line.x2, line.y2);
tx.rotate((angle - Math.PI / 2d));
Graphics2D gClone = (Graphics2D) g2d.create();
gClone.setTransform(tx);
Polygon arrowHead = new Polygon();
arrowHead.addPoint(0, 15);
arrowHead.addPoint(-15, -15);
arrowHead.addPoint(15, -15);
Area area = new Arear(arrowHead );
Area lineArea = new Area(line);
lineArea.subtract(area);
gClone.fill(area);
gClone.dispose();
我已经更改了startx和y的值，在按下鼠标时
和endx和enny在鼠标拖动
最佳答案
这是一个基本示例，演示了如何使用Path2D定义自定义形状，并使用AffineTransformation来转换形状。
此示例将导致箭头在面板上移动时指向鼠标
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class RotateArrow {
public static void main(String[] args) {
new RotateArrow();
}
public RotateArrow() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new RotatePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class RotatePane extends javax.swing.JPanel {
private Point mousePoint;
private PointyThing pointyThing;
public RotatePane() {
pointyThing = new PointyThing();
addMouseMotionListener(new MouseAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
mousePoint = e.getPoint();
repaint();
}
});
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
double rotation = 0f;
int width = getWidth() - 1;
int height = getHeight() - 1;
if (mousePoint != null) {
int x = width / 2;
int y = height / 2;
int deltaX = mousePoint.x - x;
int deltaY = mousePoint.y - y;
rotation = -Math.atan2(deltaX, deltaY);
rotation = Math.toDegrees(rotation) + 180;
}
Rectangle bounds = pointyThing.getBounds();
AffineTransform at = new AffineTransform();
at.translate((width - bounds.width) / 2, (height - bounds.height) / 2);
at.rotate(Math.toRadians(rotation), bounds.width / 2, bounds.height / 2);
Shape shape = new Path2D.Float(pointyThing, at);
g2d.setStroke(new BasicStroke(3));
g2d.setColor(Color.RED);
g2d.fill(shape);
g2d.draw(shape);
g2d.dispose();
}
}
public class PointyThing extends Path2D.Float {
public PointyThing() {
moveTo(15, 0);
lineTo(30, 15);
lineTo(0, 15);
lineTo(15, 0);
moveTo(15, 15);
lineTo(15, 60);
}
}
}
用示例二进行更新
基本上，这仅将
PointyThing用作箭头，并分别绘制线条。箭头已定向，因此它将指向直线下方（朝着鼠标）
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class RotateArrow {
public static void main(String[] args) {
new RotateArrow();
}
public RotateArrow() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new RotatePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class RotatePane extends javax.swing.JPanel {
private PointyThing pointyThing;
private Point mouseStart;
private Point mouseEnd;
public RotatePane() {
pointyThing = new PointyThing();
MouseAdapter ma = new MouseAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
mouseEnd = e.getPoint();
repaint();
}
@Override
public void mouseClicked(MouseEvent e) {
mouseStart = e.getPoint();
repaint();
}
};
addMouseListener(ma);
addMouseMotionListener(ma);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
if (mouseStart != null && mouseEnd != null) {
double rotation = 0f;
int width = getWidth() - 1;
int height = getHeight() - 1;
if (mouseEnd != null) {
int x = mouseStart.x;
int y = mouseStart.y;
int deltaX = mouseEnd.x - x;
int deltaY = mouseEnd.y - y;
rotation = -Math.atan2(deltaX, deltaY);
rotation = Math.toDegrees(rotation) + 180;
}
Rectangle bounds = pointyThing.getBounds();
g2d.setStroke(new BasicStroke(3));
g2d.setColor(Color.RED);
g2d.draw(new Line2D.Float(mouseStart, mouseEnd));
AffineTransform at = new AffineTransform();
at.translate(mouseEnd.x - (bounds.width / 2), mouseEnd.y - (bounds.height / 2));
at.rotate(Math.toRadians(rotation), bounds.width / 2, bounds.height / 2);
Shape shape = new Path2D.Float(pointyThing, at);
g2d.fill(shape);
g2d.draw(shape);
}
g2d.dispose();
}
}
public class PointyThing extends Path2D.Float {
public PointyThing() {
moveTo(15, 0);
lineTo(30, 15);
lineTo(0, 15);
lineTo(15, 0);
}
}
}