概要

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。

スクリーンショット

Swing/AnalogClock.png

サンプルコード

class AnalogClock extends JPanel {
  protected LocalTime time = LocalTime.now(ZoneId.systemDefault());
  protected Timer timer = new Timer(200, e -> {
    time = LocalTime.now(ZoneId.systemDefault());
    repaint();
  });
  private transient HierarchyListener listener;

  @Override public void updateUI() {
    removeHierarchyListener(listener);
    super.updateUI();
    listener = e -> {
      if ((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0) {
        if (e.getComponent().isShowing()) {
          // System.out.println("start");
          timer.start();
        } else {
          // System.out.println("stop");
          timer.stop();
        }
      }
    };
    addHierarchyListener(listener);
  }

  @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);
    float radius = Math.min(rect.width, rect.height) / 2f - 10f;
    g2.translate(rect.getCenterX(), rect.getCenterY());

    // Drawing the hour and minute markers
    float hourMarkerLen = radius / 6f - 10f;
    Shape hourMarker = new Line2D.Float(0f, hourMarkerLen - radius, 0f, -radius);
    Shape minuteMarker = new Line2D.Float(0f, hourMarkerLen / 2f - radius, 0f, -radius);
    AffineTransform at = AffineTransform.getRotateInstance(0d);
    g2.setStroke(new BasicStroke(2f));
    g2.setColor(Color.WHITE);
    for (int i = 0; i < 60; i++) {
      if (i % 5 == 0) {
        g2.draw(at.createTransformedShape(hourMarker));
      } else {
        g2.draw(at.createTransformedShape(minuteMarker));
      }
      at.rotate(Math.PI / 30d);
    }

    // Drawing the hour hand
    float hourHandLen = radius / 2f;
    Shape hourHand = new Line2D.Float(0f, 0f, 0f, -hourHandLen);
    double minuteRot = time.getMinute() * Math.PI / 30d;
    double hourRot = time.getHour() * Math.PI / 6d + minuteRot / 12d;
    g2.setStroke(new BasicStroke(8f));
    g2.setPaint(Color.LIGHT_GRAY);
    g2.draw(AffineTransform.getRotateInstance(hourRot).createTransformedShape(hourHand));

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

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

    g2.dispose();
  }
}
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解説

  • 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JPanelrepaint()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4fLine2Dを使用
    • この図形をLocalTime#getMinute() * 2d * Math.PI / 60分だけ回転して描画
  • 短針(hour hand)
    • 時計盤の半径の1/2の長さで太さ8fLine2Dを使用
    • この図形をLocalTime#getHour() * 2d * Math.PI / 12時間LocalTime#getMinute() * 2d * Math.PI / (12時間 * 60分)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1fLine2Dを使用
    • この図形をLocalTime#getSecond() * 2d * Math.PI / 60秒だけ回転して描画

参考リンク

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