javascript - 在 Leaflet 中绘制一条跟随移动标记的折线

Question

我有一个问题，我正在使用 Leaflet 并每 2 秒获取一次 GPS 坐标，与 map 上的移动对象有关，我成功地每 2 秒基于 gps 坐标创建了一个移动标记，但后来我无法绘制多段线在标记之后。

你有什么想法吗？谢谢

     var redraw = function(p3DMessage){

            lat = parseFloat(p3DMessage.lat);
            lng = parseFloat(p3DMessage.lon);
            console.log(lat)
            console.log(lng)


            if (theMarker != undefined) {
                  mymap.removeLayer(theMarker);
            };


            var polylinePoints = [[lat, lng]];

            //failed to draw polyline...
            //L.polyline([[lat, lng]]).addTo(mymap);      

            theMarker = L.marker([lat,lng]).addTo(mymap);  
        };

Answer 1

Polyline.addLatLng允许您向现有多段线添加一个点。

因此构建您的 map ，添加一条多段线并在您的绘图函数的每个刻度处添加一个点。请注意，您也可以重复使用您的标记。有点像

var map = L.map(document.getElementById('map')).setView([48.8583736, 2.2922926], 15);

L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
    attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
}).addTo(map);

var marker = null;
var line = L.polyline([]).addTo(map);

function redraw (p3DMessage) {
    var lat = parseFloat(p3DMessage.lat),
        lng = parseFloat(p3DMessage.lon),
        point = {lat: lat, lng: lng};

    if (!marker) {
        marker = L.marker(point).addTo(map)
    }

    line.addLatLng(point);
    marker.setLatLng(point);
}

还有一个演示

var map = L.map(document.getElementById('map')).setView([48.8583736, 2.2922926], 15);

    L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
        attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
    }).addTo(map);

    var points = [
        {lat: 48.857, lon:2.2922926},
        {lat: 48.858, lon:2.291},
        {lat: 48.859, lon:2.293},
        {lat: 48.860, lon:2.294},
        {lat: 48.862, lon:2.294},
    ];

    var marker = null;
    var line = L.polyline([]).addTo(map);

    function redraw(point) {
        if (!marker) {
            marker = L.marker(point).addTo(map)
        }
        line.addLatLng(point);
        marker.setLatLng(point);
    }

    function update() {
        if (points.length) {
            redraw(points.shift());
            setTimeout(update, 1000);
        }
    }
    setTimeout(update, 1000);

html, body {
  height: 100%;
  margin: 0;
}
#map {
  width: 100%;
  height: 100%;
}

<link rel="stylesheet" href="https://unpkg.com/leaflet@1.2.0/dist/leaflet.css" integrity="sha512-M2wvCLH6DSRazYeZRIm1JnYyh22purTM+FDB5CsyxtQJYeKq83arPe5wgbNmcFXGqiSH2XR8dT/fJISVA1r/zQ==" crossorigin=""/>
    <script src="https://unpkg.com/leaflet@1.2.0/dist/leaflet.js" integrity="sha512-lInM/apFSqyy1o6s89K4iQUKg6ppXEgsVxT35HbzUupEVRh2Eu9Wdl4tHj7dZO0s1uvplcYGmt3498TtHq+log==" crossorigin=""></script>
    
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet.draw/0.4.12/leaflet.draw.css" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet.draw/0.4.12/leaflet.draw.js"></script>

<div id='map'></div>