基于时间的图层

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const trafficLayer = new MapImageLayer({
  url: "https://traffic.arcgis.com/arcgis/rest/services/World/Traffic/MapServer",
  dpi: 48,
  imageFormat: "png32",
  refreshInterval: 3, // refresh the layer every 3 minutes
  useViewTime: false // layer sets its time extent and will ignore view's timeExtent.
});

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var clock = new Clock({
  el: "clock", // container div
  skin: "clock.svg",
  time: Date.now() // number of milliseconds elapsed since January 1, 1970, 00:00:00 UTC.
});
clock.on("time-change", setDate);

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function setDate(time) {
  // reset the clock widget show the latest traffic data if the user
  // clicks on `live` button on the clock
  if (clock.mode === "live") {
    trafficLayer.timeExtent = null;
  }
  else { // otherwise shows the traffic data where
    // the clock handles move to
    trafficLayer.timeExtent = {
      start: time,
      end: time
    };
  }
}