视图动画【译】

原文链接及内容

原文链接：https://openlayers.org/en/latest/examples/animation.html

此示例演示如何使用view.animate()方法来运行一个或多个动画。

main.js代码如下：

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';
import {easeIn, easeOut} from 'ol/easing.js';
import {fromLonLat} from 'ol/proj.js';

const london = fromLonLat([-0.12755, 51.507222]);
const moscow = fromLonLat([37.6178, 55.7517]);
const istanbul = fromLonLat([28.9744, 41.0128]);
const rome = fromLonLat([12.5, 41.9]);
const bern = fromLonLat([7.4458, 46.95]);

const view = new View({
  center: istanbul,
  zoom: 6,
});

const map = new Map({
  target: 'map',
  layers: [
    new TileLayer({
      preload: 4,
      source: new OSM(),
    }),
  ],
  view: view,
});

// A bounce easing method (from https://github.com/DmitryBaranovskiy/raphael).
function bounce(t) {
  const s = 7.5625;
  const p = 2.75;
  let l;
  if (t < 1 / p) {
    l = s * t * t;
  } else {
    if (t < 2 / p) {
      t -= 1.5 / p;
      l = s * t * t + 0.75;
    } else {
      if (t < 2.5 / p) {
        t -= 2.25 / p;
        l = s * t * t + 0.9375;
      } else {
        t -= 2.625 / p;
        l = s * t * t + 0.984375;
      }
    }
  }
  return l;
}

// An elastic easing method (from https://github.com/DmitryBaranovskiy/raphael).
function elastic(t) {
  return (
    Math.pow(2, -10 * t) * Math.sin(((t - 0.075) * (2 * Math.PI)) / 0.3) + 1
  );
}

function onClick(id, callback) {
  document.getElementById(id).addEventListener('click', callback);
}

onClick('rotate-left', function () {
  view.animate({
    rotation: view.getRotation() + Math.PI / 2,
  });
});

onClick('rotate-right', function () {
  view.animate({
    rotation: view.getRotation() - Math.PI / 2,
  });
});

onClick('rotate-around-rome', function () {
  // Rotation animation takes the shortest arc, so animate in two parts
  const rotation = view.getRotation();
  view.animate(
    {
      rotation: rotation + Math.PI,
      anchor: rome,
      easing: easeIn,
    },
    {
      rotation: rotation + 2 * Math.PI,
      anchor: rome,
      easing: easeOut,
    }
  );
});

onClick('pan-to-london', function () {
  view.animate({
    center: london,
    duration: 2000,
  });
});

onClick('elastic-to-moscow', function () {
  view.animate({
    center: moscow,
    duration: 2000,
    easing: elastic,
  });
});

onClick('bounce-to-istanbul', function () {
  view.animate({
    center: istanbul,
    duration: 2000,
    easing: bounce,
  });
});

onClick('spin-to-rome', function () {
  // Rotation animation takes the shortest arc, so animate in two parts
  const center = view.getCenter();
  view.animate(
    {
      center: [
        center[0] + (rome[0] - center[0]) / 2,
        center[1] + (rome[1] - center[1]) / 2,
      ],
      rotation: Math.PI,
      easing: easeIn,
    },
    {
      center: rome,
      rotation: 2 * Math.PI,
      easing: easeOut,
    }
  );
});

function flyTo(location, done) {
  const duration = 2000;
  const zoom = view.getZoom();
  let parts = 2;
  let called = false;
  function callback(complete) {
    --parts;
    if (called) {
      return;
    }
    if (parts === 0 || !complete) {
      called = true;
      done(complete);
    }
  }
  view.animate(
    {
      center: location,
      duration: duration,
    },
    callback
  );
  view.animate(
    {
      zoom: zoom - 1,
      duration: duration / 2,
    },
    {
      zoom: zoom,
      duration: duration / 2,
    },
    callback
  );
}

onClick('fly-to-bern', function () {
  flyTo(bern, function () {});
});

function tour() {
  const locations = [london, bern, rome, moscow, istanbul];
  let index = -1;
  function next(more) {
    if (more) {
      ++index;
      if (index < locations.length) {
        const delay = index === 0 ? 0 : 750;
        setTimeout(function () {
          flyTo(locations[index], next);
        }, delay);
      } else {
        alert('Tour complete');
      }
    } else {
      alert('Tour cancelled');
    }
  }
  next(true);
}

onClick('tour', tour);

界面布局文件index.html代码如下：

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>View Animation</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>
    <button id="rotate-left" title="Rotate clockwise">↻</button>
    <button id="rotate-right" title="Rotate counterclockwise">↺</button>
    <button id="pan-to-london">Pan to London</button>
    <button id="elastic-to-moscow">Elastic to Moscow</button>
    <button id="bounce-to-istanbul">Bounce to Istanbul</button>
    <button id="spin-to-rome">Spin to Rome</button>
    <button id="fly-to-bern">Fly to Bern</button>
    <button id="rotate-around-rome">Rotate around Rome</button>
    <button id="tour">Take a tour</button>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>