---
category: swing
folder: AnalogClock
title: Timerを使用してJPanelにアナログ時計の針を描画する
tags: [AffineTransform, JPanel, Animation]
author: aterai
pubdate: 2021-05-10T02:47:21+09:00
description: javax.swing.Timerを使用して現在時刻の取得し、JPanel上にアナログ時計の針の描画します。
image: https://drive.google.com/uc?id=1w1gUIi7WDcTNi9JItoyXPOorketpHDJW
---
* 概要 [#summary]
`javax.swing.Timer`を使用して現在時刻の取得し、`JPanel`上にアナログ時計の針の描画します。

#download(https://drive.google.com/uc?id=1w1gUIi7WDcTNi9JItoyXPOorketpHDJW)

* サンプルコード [#sourcecode]
#code(link){{
JPanel clock = new JPanel() {
  @Override protected void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
    Rectangle rect = SwingUtilities.calculateInnerArea(this, null);
    g2.setColor(Color.BLACK);
    g2.fill(rect);
    g2.setColor(Color.WHITE);
    g2.translate(rect.getCenterX(), rect.getCenterY());
    float radius = Math.min(rect.width, rect.height) / 2f - 10f;

    // Drawing the hour markers
    float hourMarkerLen = radius / 6f - 10f;
    Shape hourMarker = new Line2D.Float(0f, hourMarkerLen - radius, 0f, -radius);
    AffineTransform at = AffineTransform.getRotateInstance(0d);
    for (int i = 0; i < 12; i++) {
      at.rotate(Math.PI / 6d);
      g2.draw(at.createTransformedShape(hourMarker));
    }

    // Drawing the minute hand
    float minuteHandLen = 5f * radius / 6f;
    Shape minuteHand = new Line2D.Float(0f, 0f, 0f, -minuteHandLen);
    AffineTransform at2 = AffineTransform.getRotateInstance(
        time.getMinute() * Math.PI / 30d);
    g2.setStroke(new BasicStroke(4f));
    g2.setPaint(Color.WHITE);
    g2.draw(at2.createTransformedShape(minuteHand));

    // Drawing the hour hand
    float hourHandLen = radius / 3f;
    Shape hourHand = new Line2D.Float(0f, 0f, 0f, -hourHandLen);
    AffineTransform at3 = AffineTransform.getRotateInstance(
        time.getHour() * Math.PI / 6d);
    g2.setStroke(new BasicStroke(8f));
    g2.draw(at3.createTransformedShape(hourHand));

    // Drawing the second hand
    float r = radius / 6f;
    float secondHandLen = radius - r;
    Shape secondHand = new Line2D.Float(0f, r, 0f, -secondHandLen);
    AffineTransform at1 = AffineTransform.getRotateInstance(
        time.getSecond() * Math.PI / 30d);
    g2.setPaint(Color.RED);
    g2.setStroke(new BasicStroke(1f));
    g2.draw(at1.createTransformedShape(secondHand));
    g2.fill(new Ellipse2D.Float(-r / 4f, -r / 4f, r / 2f, r / 2f));

    g2.dispose();
  }
};

new Timer(200, e -> {
  time = LocalTime.now(ZoneId.systemDefault());
  clock.repaint();
}).start();
}}

* 解説 [#explanation]
- `javax.swing.Timer`
-- `200`ミリ秒ごとに`LocalTime.now(ZoneId.systemDefault())`で現在時刻を取得し、アナログ時計を描画する`JPanel`を`repaint()`メソッドで再描画
- 長針(`minute hand`)
-- 時計盤の半径の`5/6`の長さで太さ`4f`の`Line2D`を使用
-- この図形を`AffineTransform.getRotateInstance(...).createTransformedShape(Shape)`で`LocalTime#getMinute() * 2d * Math.PI / 60d`だけ回転して描画
- 短針(`hour hand`)
-- 時計盤の半径の`1/3`の長さで太さ`8f`の`Line2D`を使用
-- この図形を`AffineTransform.getRotateInstance(...).createTransformedShape(Shape)`で`LocalTime#getHour() * 2d * Math.PI / 12d`だけ回転して描画
- 秒針(`second hand`)
-- 時計盤の半径より少し短く太さ`1f`の`Line2D`を使用
-- この図形を`AffineTransform.getRotateInstance(...).createTransformedShape(Shape)`で`LocalTime#getSecond() * 2d * Math.PI / 60d`だけ回転して描画

* 参考リンク [#reference]
- [https://stackoverflow.com/questions/26211683/analog-clock-working-but-seconds-repainting java - Analog Clock working but seconds repainting - Stack Overflow]
- [https://stackoverflow.com/questions/49740199/java-analogue-clock swing - Java analogue clock - Stack Overflow]
- [https://stackoverflow.com/questions/58217509/how-to-fix-the-clock-from-flickering java - How to fix the clock from flickering? - Stack Overflow]
- [[Fontを回転する>Swing/TransformedShape]]

* コメント [#comment]
#comment
#comment