自定义拖拽上传展示数据（KMZ）

本示例演示使用自定义格式拖拽交互加载处理 KMZ 文件.

本示例演示使用自定义格式拖拽交互加载处理 KMZ 文件。除了在 Drag-and-Drop 示例中的格式之外，还支持自定义格式（subclassing KML）来处理 KMZ 文件。 KML and 图标（icons）必须从 KMZ 数组缓存中同步提取。使用JSZip 2.x 的原因是，JSZip 2.x 有更好的浏览器兼容性，并且比较新的 JSZip-sync. 更容易上手编码。此方法不支持投影坐标系转换，因此仅支持渲染 EPSG:4326 和 EPSG:3857 投影坐标系数据。

main.js

import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {
  DragAndDrop,
  defaults as defaultInteractions,
} from 'ol/interaction.js';
import {GPX, GeoJSON, IGC, KML, TopoJSON} from 'ol/format.js';
import {OSM, Vector as VectorSource} from 'ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';

// Create functions to extract KML and icons from KMZ array buffer,
// which must be done synchronously.

const zip = new JSZip();

function getKMLData(buffer) {
  let kmlData;
  zip.load(buffer);
  const kmlFile = zip.file(/\.kml$/i)[0];
  if (kmlFile) {
    kmlData = kmlFile.asText();
  }
  return kmlData;
}

function getKMLImage(href) {
  const index = window.location.href.lastIndexOf('/');
  if (index !== -1) {
    const kmlFile = zip.file(href.slice(index + 1));
    if (kmlFile) {
      return URL.createObjectURL(new Blob([kmlFile.asArrayBuffer()]));
    }
  }
  return href;
}

// Define a KMZ format class by subclassing ol/format/KML

class KMZ extends KML {
  constructor(opt_options) {
    const options = opt_options || {};
    options.iconUrlFunction = getKMLImage;
    super(options);
  }

  getType() {
    return 'arraybuffer';
  }

  readFeature(source, options) {
    const kmlData = getKMLData(source);
    return super.readFeature(kmlData, options);
  }

  readFeatures(source, options) {
    const kmlData = getKMLData(source);
    return super.readFeatures(kmlData, options);
  }
}

// Set up map with Drag and Drop interaction

const dragAndDropInteraction = new DragAndDrop({
  formatConstructors: [KMZ, GPX, GeoJSON, IGC, KML, TopoJSON],
});

const map = new Map({
  interactions: defaultInteractions().extend([dragAndDropInteraction]),
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
  ],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});

dragAndDropInteraction.on('addfeatures', function (event) {
  const vectorSource = new VectorSource({
    features: event.features,
  });
  map.addLayer(
    new VectorLayer({
      source: vectorSource,
    })
  );
  map.getView().fit(vectorSource.getExtent());
});

const displayFeatureInfo = function (pixel) {
  const features = [];
  map.forEachFeatureAtPixel(pixel, function (feature) {
    features.push(feature);
  });
  if (features.length > 0) {
    const info = [];
    let i, ii;
    for (i = 0, ii = features.length; i < ii; ++i) {
      const description =
        features[i].get('description') ||
        features[i].get('name') ||
        features[i].get('_name') ||
        features[i].get('layer');
      if (description) {
        info.push(description);
      }
    }
    document.getElementById('info').innerHTML = info.join('<br/>') || '&nbsp';
  } else {
    document.getElementById('info').innerHTML = '&nbsp;';
  }
};

map.on('pointermove', function (evt) {
  if (evt.dragging) {
    return;
  }
  const pixel = map.getEventPixel(evt.originalEvent);
  displayFeatureInfo(pixel);
});

map.on('click', function (evt) {
  displayFeatureInfo(evt.pixel);
});

// Sample data download

const link = document.getElementById('download');

function download(fullpath, filename) {
  fetch(fullpath)
    .then(function (response) {
      return response.blob();
    })
    .then(function (blob) {
      link.href = URL.createObjectURL(blob);
      link.download = filename;
      link.click();
    });
}

document.getElementById('download-kmz').addEventListener('click', function () {
  download('data/kmz/iceland.kmz', 'iceland.kmz');
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Custom Drag-and-Drop (KMZ)</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
      #info {
        width: 100%;
        height: 24rem;
        overflow: scroll;
        display: flex;
        align-items: baseline;
        border: 1px solid black;
        justify-content: flex-start;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <br />
    <div>
      <a id="download" download></a>
      <button id="download-kmz">Download sample</button>
    </div>
    <br />
    <div id="info">&nbsp;</div>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="./resources/elm-pep.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jszip/2.6.1/jszip.min.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "drag-and-drop-custom-kmz",
  "dependencies": {
    "ol": "7.3.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}