Google map polyLine not clearing

问题:

I have a sample google map here where I can draw a polyline and drag the marker to redraw the polyline. When I'm dragging the marker, I'm usingPath.setMap(null) to redraw the Polyline as,

  google.maps.event.addListener(marker, 'dragend', function(event) {

                    var newLatLng = event.latLng;

                    var index = Latlngs.map(function(element) {
                        return element[0];
                    }).indexOf(marker.id);
                    if (index !== -1) {
                        Latlngs[index] = [marker.id, newLatLng];
                    }

                    console.log(Latlngs);
                    var changedLine=[];
                    for (var i = 0; i < Latlngs.length; i++) {
                        changedLine.push(Latlngs[i][1]);
                    }
                    console.log(changedLine);
                     Path.setMap(null);
                     draw(changedLine, map);
                });

But the polyline is not clearing as required. How can I clear old path and redraw the same?

回答1:

The issue is the creation of the markers. When you create a new Marker you call draw without removing the existing Polyline(Path)

This would fix it:

        function placeMarkerAndPanTo(latLng, map) {

            var marker = new google.maps.Marker({
                position: latLng,
                map: map,
                draggable: true
            });
            markers.push(marker);
            marker.id = uniqueId;
            Latlngs.push([uniqueId, latLng]);
            uniqueId++;
            console.log(Latlngs);

          //draw(Line, map);

            google.maps.event.addListener(marker, 'dragend', function(event) {
                if(Path)Path.setMap(null);
                var newLatLng = event.latLng;

                var index = Latlngs.map(function(element) {
                    return element[0];
                }).indexOf(marker.id);
                if (index !== -1) {
                    Latlngs[index] = [marker.id, newLatLng];
                }


                var changedLine=[];
                for (var i = 0; i < Latlngs.length; i++) {
                    changedLine.push(Latlngs[i][1]);
                }


                 draw(changedLine, map);
            });
            google.maps.event.trigger(marker,'dragend',
                                      {latLng:marker.getPosition()})

        }

But there is no need to draw a new Polyline, polylines-pathes may be modified directly:

function initMap() {
    var goo     = google.maps,
        map     = new goo.Map(document.getElementById('map'), {
                    zoom: 10,
                    center: new goo.LatLng(12.8799313333, 77.5991386667)
                  }),
        line    = new goo.Polyline({
                                      path:[],
                                      geodesic: true,
                                      strokeColor: '#FF0000',
                                      strokeOpacity: 1.0,
                                      strokeWeight: 2 ,
                                      map:map
                                   }),
        markers = new goo.MVCArray;
        
        goo.event.addListener(map, 'click', function(e) {
          var marker = new goo.Marker({ position:e.latLng,
                                        map:map,
                                        draggable:true});
          markers.push(marker);
          //push new point to the path
          line.getPath().push(marker.getPosition());
          
          goo.event.addListener(marker,'dragend',function(){
            //simply update the path
            line.getPath().setAt(markers.indexOf(this),
                                 this.getPosition());
          });
          goo.event.addListener(marker,'dblclick',function(){
            //remove marker and path-point
            line.getPath().removeAt(markers.indexOf(this));
            markers.removeAt(markers.indexOf(this));
            this.setMap(null)
          });
        });


  }

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

<div id="map"></div>
<script src="https://maps.googleapis.com/maps/api/js?v=3&callback=initMap"></script>