View 最小等级

本示例演示改变 view 的最大最小等级.

view 的 minZoom 选项参数限制地图等级。此属性可以通过调用 view.setMinZoom(newMinZoom) 来改变。在本示例中，已经设置最小地图等级，因此可以一个看到一个世界。改变浏览器的窗口来改变阈值。

main.js

import Map from 'ol/Map.js';
import OSM from 'ol/source/OSM.js';
import TileLayer from 'ol/layer/Tile.js';
import View from 'ol/View.js';

const viewport = document.getElementById('map');

function getMinZoom() {
  const width = viewport.clientWidth;
  return Math.ceil(Math.LOG2E * Math.log(width / 256));
}

const initialZoom = getMinZoom();

const view = new View({
  center: [0, 0],
  minZoom: initialZoom,
  zoom: initialZoom,
});

const map = new Map({
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
  ],
  target: 'map',
  view: view,
});

window.addEventListener('resize', function () {
  const minZoom = getMinZoom();
  if (minZoom !== view.getMinZoom()) {
    view.setMinZoom(minZoom);
  }
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>View Min-Zoom</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <!-- 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": "min-zoom",
  "dependencies": {
    "ol": "7.3.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}