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javascriptgoogle-mapsgoogle-maps-api-3polyline

Google Maps Polyline click between points

Using Google Maps api 3, I have a polyline with a click event. I need to find out between which two points in the path the user has clicked. Ideally the index of the points.

Below is a sample page mostly taken direct from google docs, but added the click event. The actual app has much more complex polylines.

Is there are way to do this?

Many thanks

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no">
<meta charset="utf-8">
<title>Polylines</title>
<style>    
  #map {
    height: 100%;
  }
  /* Optional: Makes the sample page fill the window. */
  html, body {
    height: 100%;
    margin: 0;
    padding: 0;
  }
  </style>
 </head>
 <body>
      <div id="map"></div>
      <script>
      function initMap() {
          var map = new google.maps.Map(document.getElementById('map'), {
          zoom: 3,
          center: {lat: 0, lng: -180},
          mapTypeId: 'terrain'
      });

      var flightPlanCoordinates = [
         {lat: 37.772, lng: -122.214},
         {lat: 21.291, lng: -157.821},
         {lat: -18.142, lng: 178.431},
         {lat: -27.467, lng: 153.027}
      ];

      var poly = new google.maps.Polyline({
         path: flightPlanCoordinates,
         geodesic: true,
         strokeColor: '#FF0000',
         strokeOpacity: 1.0,
         strokeWeight: 2
       });

       poly.setMap(map);


       google.maps.event.addListener(poly, 'click', function(e) {            
         alert(JSON.stringify(e));
       });

     }
</script>
<script async defer
src="https://maps.googleapis.com/maps/api/js?key=MYAPIKEY&callback=initMap">
</script>

Solution

  • The following quick and dirty code may not be the best and can surly be optimized, but I work since year with it.

    This code i have in the poly click event:

        rc = getNearestVertex(poly, event.latLng);
    x = rc.split(":");  //rc = "index:minDiff"
    vertIndex = x[0] *1;
    markerIndexes = vertIndex + ',' +(vertIndex + 1);

    I use it to mark the point before and the point after the marker on the polyline. Following the function:

    function getNearestVertex(poly, pLatLng) {
    // test to get nearest point on poly to the pLatLng point
    // click is on poly, so the nearest vertex is the smallest diff between
    var minDist = 9999999999;
    var minDiff = 9999999999;
    var path = poly.getPath();
    var count = path.length || 0;

    for (var n = 0; n < count - 1; n++) {
        if (n == 0) {
            point = path.getAt(n); 
            dist = g.geometry.spherical.computeDistanceBetween(pLatLng, point);
        }
        //g.geometry.spherical.computeDistanceBetween(aLatLng, bLatLng)
        var pointb = path.getAt(n + 1);
        distb =  g.geometry.spherical.computeDistanceBetween(pLatLng, pointb);
        distp2p = g.geometry.spherical.computeDistanceBetween(point, pointb);
        var pdiff = dist + distb - distp2p;

        //alert(n + " / " +dist +" + " +distb +" - " +distp2p +" = " +pdiff);
        if (pdiff < minDiff) {
            minDiff = pdiff.toFixed(3);
            index = n;
        }
        point = pointb;
        dist = distb;
    } //-> end for
    //alert(index +":" + minDiff);
    return index +":" + minDiff;
} //-> end of getNearestVertex

    Perhaps someone with better js and math. knowledge can jump in and improve the code. However as said it works for me, whereby my track-points for my bicycle tours are very seldom over 2-3-tsd. points