聚合标注

TIP

聚合标注是在不同地图分辨率下，通过聚合方式展现标注点的一种方法。

代码如下:

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<template>
  <div id="top">
    <el-button type="primary" @click="handleAdd">添加聚合标注</el-button>
    <el-button type="danger" @click="handleDelete">移除聚合标注</el-button>
  </div>
  <div id="map"></div>
</template>

<script lang="ts" setup>
import { onMounted, onBeforeUnmount } from "vue";
import { Map, View } from "ol";
import { Tile as TileLayer } from "ol/layer";
import { defaults, FullScreen } from "ol/control";
import { XYZ } from "ol/source";
import { ATTRIBUTIONS, MAPURL } from "../../../constants";
import { addClusterLabels, removeClusterLabels, clusters } from "./clusters";
let map: Map | null = null;
const raster = new TileLayer({
  source: new XYZ({
    attributions: ATTRIBUTIONS,
    url: MAPURL,
    maxZoom: 20,
  }),
});
const initMap = () => {
  map = new Map({
    //初始化map
    target: "map",
    //地图容器中加载的图层
    layers: [
      //加载瓦片图层数据
      raster,
      clusters, // 聚合标注图层
    ],
    view: new View({
      center: [0, 0],
      minZoom: 2,
      zoom: 2,
    }),
    //加载控件到地图容器中
    controls: defaults().extend([
      new FullScreen(), //加载全屏显示控件（目前支持非IE内核浏览器）
    ]),
  });
};
// 添加聚合要素
const handleAdd = () => {
  if (map) {
    addClusterLabels(map);
  }
};

// 移除聚合要素
const handleDelete = () => {
  if (map) {
    removeClusterLabels(map);
  }
};

onMounted(() => {
  initMap();
  if (map) {
    removeClusterLabels(map);
  }
});

onBeforeUnmount(() => {
  if (map) {
    map.dispose();
    map = null;
  }
});
</script>

<!-- Add "scoped" attribute to limit CSS to this component only -->
<style scoped>
#map {
  height: 650px;
}
#top {
  text-align: center;
  height: 50px;
  line-height: 50px;
}
</style>

clusters 代码如下：

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import { Feature, Map } from 'ol'
import { Point } from 'ol/geom'
import { Vector as VectorSource, Cluster } from 'ol/source'
import { Vector as VectorLayer } from 'ol/layer'
import { Style, Circle, Stroke, Fill, Text } from 'ol/style'

//此示例创建10000个要素
const count = 10000
const features: Feature<Point>[] = new Array(count)
const e = 4500000
for (let i = 0; i < count; ++i) {
  const coordinates = [2 * e * Math.random() - e, 2 * e * Math.random() - e]
  features[i] = new Feature(new Point(coordinates))
}
//矢量要素数据源
const source = new VectorSource({
  features: features,
})
//聚合标注数据源
const clusterSource = new Cluster({
  distance: 40,
  source: source,
})
//加载聚合标注的矢量图层
const styleCache = {}
export const clusters = new VectorLayer({
  source: clusterSource,
  style: (feature): Style[] => {
    const size: number = feature.get('features').length
    let style: Style[] = styleCache[size]
    if (!style) {
      style = [
        new Style({
          image: new Circle({
            radius: 10,
            stroke: new Stroke({
              color: '#fff',
            }),
            fill: new Fill({
              color: '#3399CC',
            }),
          }),
          text: new Text({
            text: size.toString(),
            fill: new Fill({
              color: '#fff',
            }),
          }),
        }),
      ]
      styleCache[size] = style
    }
    return style
  },
})

/**
 * 添加聚合要素
 * @param {ol.Map} map 地图实例
 */
export const addClusterLabels = (map: Map) => {
  //当前聚合标注数据源中的要素
  const currentFeatrues = clusterSource?.getSource()?.getFeatures()
  //如果聚合标注数据源中没有要素，则重新添加要素
  if (currentFeatrues && currentFeatrues.length == 0) {
    clusterSource?.getSource()?.addFeatures(features)
    clusters.setSource(clusterSource)
    map.addLayer(clusters)
  }
}

/**
 * 移除聚合要素
 * @param {ol.Map} map 地图实例
 */
export const removeClusterLabels = (map: Map) => {
  //当前聚合标注数据源中的要素
  const currentFeatrues = clusterSource?.getSource()?.getFeatures()
  //如果聚合标注数据源中没有要素，则重新添加要素
  if (currentFeatrues && currentFeatrues.length != 0) {
    //移除聚合标注数据源中的所有要素
    clusterSource?.getSource()?.clear()
    //移除标注图层
    map.removeLayer(clusters)
  }
}