HarmonyOS NEXT 使用Canvas实现模拟时钟案例

// 初始化表盘和表针对应的变量，并首次绘制。
private init() {
  let clockBgSource = image.createImageSource(this.resourceDir + '/' + CLOCK_BG_PATH);
  let hourSource = image.createImageSource(this.resourceDir + '/' + CLOCK_HOUR_PATH);
  let minuteSource = image.createImageSource(this.resourceDir + '/' + CLOCK_MINUTE_PATH);
  let secondSource = image.createImageSource(this.resourceDir + '/' + CLOCK_SECOND_PATH);

  const now = new Date();
  const currentHour = now.getHours();
  const currentMinute = now.getMinutes();
  const currentSecond = now.getSeconds();
  this.time = this.getTime(currentHour, currentMinute, currentSecond);

  // 创建表盘对应的PixelMap并绘制。
  let paintDial = clockBgSource.createPixelMap().then((pixelMap: image.PixelMap) => {
    this.clockPixelMap = pixelMap;
    this.paintDial();
  }).catch((err: BusinessError) => {
    logger.error(`[error]error at clockBgSource.createPixelMap:${err.message}`);
  });

  // 创建时针对应的PixelMap并绘制。
  hourSource.createPixelMap().then(async (pixelMap: image.PixelMap) => {
    await paintDial;
    const hourOffset = currentMinute / 2;
    this.paintPin(ANGLE_PRE_HOUR * currentHour + hourOffset, pixelMap);
    this.hourPixelMap = pixelMap;
  }).catch((err: BusinessError) => {
    logger.error(`[error]error at hourSource.createPixelMap:${err.message}`);
  });

  ...
}

// 2.监听时间变化，每秒重新绘制一次
this.timeListener = new TimeChangeListener(
  (hour: number, minute: number, second: number) => {
    this.renderContext.clearRect(-this.clockRadius, -this.clockRadius, this.canvasSize, this.canvasSize);
    this.paintDial();
    this.timeChanged(hour, minute, second);
    this.time = this.getTime(hour, minute, second);
  },
);

// 绘制表针
private paintPin(degree: number, pinImgRes: image.PixelMap | null) {
  // TODO：知识点：先将当前绘制上下文保存再旋转画布，先保存旋转前的状态，避免状态混乱。
  this.renderContext.save();
  const angleToRadian = Math.PI / 180;
  let theta = degree * angleToRadian;
  this.renderContext.rotate(theta);
  this.renderContext.beginPath();
  if (pinImgRes) {
    this.renderContext.drawImage(
      pinImgRes,
      -IMAGE_WIDTH / 2,
      -this.clockRadius,
      IMAGE_WIDTH,
      this.canvasSize);
  } else {
    logger.error('PixelMap is null!');
  }
  this.renderContext.restore();
}

analogclock                             // har类型
|---src/main/ets/pages
|   |---AnalogClock.ets                 // 页面及时钟绘制的主要逻辑
|   |---TimeChangeListener.ets          // 时间变化监听文件