---
category: swing
folder: ArrowLines
title: JPanelに矢印付きの直線を描画する
tags: [JPanel, Path2D, AffineTransform]
author: aterai
pubdate: 2020-09-14T01:14:39+09:00
description: JPanel上にPath2Dを使用して作成した矢印付きの直線を描画します。
image: https://drive.google.com/uc?id=1VDPfzAYOCu-8IfK1RdpFDm7SLdSrGH-E
---
* Summary [#summary]
`JPanel`上に`Path2D`を使用して作成した矢印付きの直線を描画します。
#download(https://drive.google.com/uc?id=1VDPfzAYOCu-8IfK1RdpFDm7SLdSrGH-E)
* Source Code Examples [#sourcecode]
#code(link){{
class Arrow {
private final Point start = new Point();
private final Point end = new Point();
private final Path2D arrowHead;
protected Arrow(Point start, Point end) {
this.start.setLocation(start);
this.end.setLocation(end);
arrowHead = makeArrowHead(new Dimension(8, 8));
}
protected Path2D makeArrowHead(Dimension size) {
Path2D path = new Path2D.Double();
double t = size.height;
double w = size.width * .5;
path.moveTo(0d, -w);
path.lineTo(t, 0d);
path.lineTo(0d, w);
path.closePath();
return path;
}
public void draw(Graphics2D g2) {
g2.drawLine(start.x, start.y, end.x, end.y);
arrowHead.transform(AffineTransform.getRotateInstance(
end.getX() - start.getX(), end.getY() - start.getY()));
arrowHead.transform(AffineTransform.getTranslateInstance(
end.getX(), end.getY()));
g2.fill(arrowHead);
g2.draw(arrowHead);
}
}
}}
* Description [#explanation]
* Description [#description]
- 矢印として座標原点上に底辺の中央が配置される二等辺三角形を`Path2D`で作成
- 直線の始点と終点から回転ベクトルを計算して`AffineTransform.getRotateInstance(double vecx, double vecy)`メソッドで`AffineTransform`オブジェクトを作成し、`Path2D#transform(AffineTransform)`メソッドで矢印を座標原点を中心に回転
- `AffineTransform.getTranslateInstance(end.getX(), end.getY())`メソッドで`AffineTransform`オブジェクトを作成し、`Path2D#transform(AffineTransform)`メソッドで直線の終点まで矢印を移動
* Reference [#reference]
- [https://stackoverflow.com/questions/2027613/how-to-draw-a-directed-arrow-line-in-java drawing - How to draw a directed arrow line in Java? - Stack Overflow]
* Comment [#comment]
#comment
#comment