Realtime Stream

<!--
  示例：实时数据流
  核心逻辑：定时把新点位并入数组，setData 全量替换，只保留最近 40 条
  依赖：MapLibre GL JS 4 · jsDelivr CDN · demotiles 样式
-->
<!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>实时数据流</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/maplibre-gl@4/dist/maplibre-gl.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;color:#16181d}
  .bar{flex:0 0 auto;display:flex;gap:12px;align-items:center;padding:8px 12px;
       background:#f6f7f9;border-bottom:1px solid #e3e6ea;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar b{color:#16181d;font-weight:600}
  .btn{border:1px solid #cdd3db;background:#fff;border-radius:4px;padding:3px 9px;
       font:12px/1.5 inherit;color:#16181d;cursor:pointer}
  #map{flex:1 1 auto;min-height:0}
</style>
</head>
<body>
<div class="bar">
  <button class="btn" id="toggle">暂停</button>
  <span>缓冲 <b id="n">0</b> 条</span>
  <span>最新 <b id="last">—</b></span>
  <span>每 0.9 秒推入一条</span>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/maplibre-gl@4/dist/maplibre-gl.js"></script>
<script>
(function () {
  'use strict';

  if (typeof maplibregl === 'undefined') {
    document.body.innerHTML =
      '<div style="padding:24px;color:#b42318">MapLibre 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var MAX = 40;
  var points = [];
  var seq = 1;

  var map = new maplibregl.Map({
    container: 'map',
    style: 'https://demotiles.maplibre.org/style.json',
    center: [120.2, 30.25],
    zoom: 8.6,
    attributionControl: { compact: true, customAttribution: 'MapLibre demo tiles' }
  });

  map.addControl(new maplibregl.NavigationControl(), 'top-right');

  function collection() {
    return {
      type: 'FeatureCollection',
      features: points.map(function (p) {
        return {
          type: 'Feature',
          properties: { seq: p.seq, value: p.value },
          geometry: { type: 'Point', coordinates: [p.lng, p.lat] }
        };
      })
    };
  }

  map.on('load', function () {
    map.addSource('live', { type: 'geojson', data: collection() });

    map.addLayer({
      id: 'live-halo',
      type: 'circle',
      source: 'live',
      paint: {
        'circle-radius': 13,
        'circle-color': '#e8590c',
        'circle-opacity': 0.16
      }
    });

    map.addLayer({
      id: 'live',
      type: 'circle',
      source: 'live',
      paint: {
        'circle-radius': ['step', ['get', 'value'], 4, 40, 6, 70, 8],
        'circle-color': [
          'step', ['get', 'value'],
          '#4a90c9', 40, '#e8590c', 70, '#b42318'
        ],
        'circle-stroke-color': '#ffffff',
        'circle-stroke-width': 1.2
      }
    });
  });

  function push() {
    points.push({
      lng: 120.05 + Math.random() * 0.32,
      lat: 30.12 + Math.random() * 0.28,
      value: Math.round(15 + Math.random() * 85),
      seq: seq++
    });
    if (points.length > MAX) points.shift();

    var src = map.getSource('live');
    if (src) src.setData(collection());

    var last = points[points.length - 1];
    document.getElementById('n').textContent = points.length;
    document.getElementById('last').textContent =
      last.value + ' · #' + last.seq;
  }

  var timer = setInterval(push, 900);
  push();

  document.getElementById('toggle').addEventListener('click', function () {
    if (timer) {
      clearInterval(timer);
      timer = null;
      this.textContent = '继续';
    } else {
      timer = setInterval(push, 900);
      this.textContent = '暂停';
    }
  });

  map.on('error', function (e) {
    if (e.error) console.warn('地图错误：' + e.error.message);
  });
})();
</script>
</body>
</html>