Tile Load Progress

<!--
  示例：瓦片加载进度
  要点：监听 tileloadstart / tileloadend / tileloaderror，用计数器换算进度条
  依赖：OpenLayers 10.3.1 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>瓦片加载进度</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.css">
<style>
  html,body{height:100%;margin:0}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:10px;align-items:center;font-size:12px;color:#58606e}
  .bar button{padding:4px 10px;border:1px solid #cfd4dc;border-radius:4px;
              background:#fff;cursor:pointer;font-size:12px}
  .track{width:120px;height:6px;border-radius:3px;background:#e2e6ec;overflow:hidden}
  .fill{height:100%;width:0;background:#1f5fd0;transition:width .2s linear}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <div class="track"><div class="fill" id="fill"></div></div>
  <span id="info">—</span>
  <button id="reset">重置统计</button>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    document.getElementById('map').innerHTML =
      '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var base = new ol.layer.Tile({ source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'}) });
  var source = base.getSource();
  var pending = 0;
  var done = 0;
  var failed = 0;

  var fill = document.getElementById('fill');
  var info = document.getElementById('info');

  function report() {
    var total = done + failed + pending;
    var pct = total === 0 ? 100 : Math.round((done + failed) / total * 100);
    fill.style.width = pct + '%';
    info.textContent = '完成 ' + done + ' · 失败 ' + failed + ' · 进行中 ' + pending;
  }

  source.on('tileloadstart', function () {
    pending++;
    report();
  });

  source.on('tileloadend', function () {
    pending = Math.max(0, pending - 1);
    done++;
    report();
  });

  source.on('tileloaderror', function () {
    pending = Math.max(0, pending - 1);
    failed++;
    report();
  });

  /* 监听就绪后再建地图，首屏瓦片也能统计 */
  new ol.Map({
    target: 'map',
    layers: [base],
    view: new ol.View({
      center: ol.proj.fromLonLat([116.3974, 39.9093]),
      zoom: 13
    }),
    controls: ol.control.defaults.defaults({ attribution: false })
  });

  document.getElementById('reset').addEventListener('click', function () {
    pending = 0;
    done = 0;
    failed = 0;
    report();
  });

  report();
})();
</script>
</body>
</html>