高级地图定位

(最佳适应，使用extent定位).
(限制最小分辨率),

This example demonstrates how a map's view can be adjusted so a geometry or coordinate is positioned at a specific pixel location.

本示例演示，通过调整地图视野（view），使 geometry 或者 coordinate 定位在明确的像素位置。

示例中，在 map 容器中，增加了五个 div （四个用来 padding，一个用来 centerOn ），使用 css 设置相对于 viewport 的 padding ，使地图看起来位置是偏移的。而 map 的定位方法，比如 fit 和 centerOn ，也可以通过传入相同的 padding 值来确保定位是精准的。

view 对象的 fit 方法可以传入相同的 padding 参数来进行准确定位。

view 对象的 centerOn 方法用来定位一个 coordinate 到明确的像素位置（即第五个div-地图中的小黑框）。

使用 Alt+Shift+Drag 来旋转地图。

注意: 本示例不改变 view 的中心点。因此缩放控制和旋转地图仍然会使用 viewport 作为锚点。如果想基于 padding 改变整个 view 位置，可以在创建 view 时候使用 padding 参数，就像 view-padding.html示例中一样。

main.js

import GeoJSON from 'ol/format/GeoJSON.js';
import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {OSM, Vector as VectorSource} from 'ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';

const source = new VectorSource({
  url: 'data/geojson/switzerland.geojson',
  format: new GeoJSON(),
});

const vectorLayer = new VectorLayer({
  source: source,
  style: {
    'fill-color': 'rgba(255, 255, 255, 0.6)',
    'stroke-width': 1,
    'stroke-color': '#319FD3',
    'circle-radius': 5,
    'circle-fill-color': 'rgba(255, 255, 255, 0.6)',
    'circle-stroke-width': 1,
    'circle-stroke-color': '#319FD3',
  },
});

const view = new View({
  center: [0, 0],
  zoom: 1,
});
const map = new Map({
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
    vectorLayer,
  ],
  target: 'map',
  view: view,
});

const zoomtoswitzerland = document.getElementById('zoomtoswitzerland');
zoomtoswitzerland.addEventListener(
  'click',
  function () {
    const feature = source.getFeatures()[0];
    const polygon = feature.getGeometry();
    view.fit(polygon, {padding: [170, 50, 30, 150]});
  },
  false
);

const zoomtolausanne = document.getElementById('zoomtolausanne');
zoomtolausanne.addEventListener(
  'click',
  function () {
    const feature = source.getFeatures()[1];
    const point = feature.getGeometry();
    view.fit(point, {padding: [170, 50, 30, 150], minResolution: 50});
  },
  false
);

const centerlausanne = document.getElementById('centerlausanne');
centerlausanne.addEventListener(
  'click',
  function () {
    const feature = source.getFeatures()[1];
    const point = feature.getGeometry();
    const size = map.getSize();
    view.centerOn(point.getCoordinates(), size, [570, 500]);
  },
  false
);

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Advanced View Positioning</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
      .mapcontainer {
        position: relative;
        margin-bottom: 20px;
      }
      .map {
        width: 1000px;
        height: 600px;
      }
      .map .ol-zoom {
        top: 178px;
        left: 158px;
      }
      .map .ol-rotate {
        top: 178px;
        right: 58px;
      }
      .map .ol-attribution,
      .map .ol-attribution.ol-uncollapsible {
        bottom: 30px;
        right: 50px;
      }
      .padding-top {
        position: absolute;
        top: 0;
        left: 0px;
        width: 1000px;
        height: 170px;
        background: rgba(255, 255, 255, 0.5);
      }
      .padding-left {
        position: absolute;
        top: 170px;
        left: 0;
        width: 150px;
        height: 400px;
        background: rgba(255, 255, 255, 0.5);
      }
      .padding-right {
        position: absolute;
        top: 170px;
        left: 950px;
        width: 50px;
        height: 400px;
        background: rgba(255, 255, 255, 0.5);
      }
      .padding-bottom {
        position: absolute;
        top: 570px;
        left: 0px;
        width: 1000px;
        height: 30px;
        background: rgba(255, 255, 255, 0.5);
      }
      .center {
        position: absolute;
        border: solid 1px black;
        top: 490px;
        left: 560px;
        width: 20px;
        height: 20px;
      }
    </style>
  </head>
  <body>
    <div class="mapcontainer">
      <div id="map" class="map"></div>
      <div class="padding-top"></div>
      <div class="padding-left"></div>
      <div class="padding-right"></div>
      <div class="padding-bottom"></div>
      <div class="center"></div>
    </div>
    <button id="zoomtoswitzerland">Zoom to Switzerland</button> (best fit).<br/>
    <button id="zoomtolausanne">Zoom to Lausanne</button> (with min resolution),<br/>
    <button id="centerlausanne">Center on Lausanne</button>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="./resources/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "center",
  "dependencies": {
    "ol": "7.3.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}