flutter - Flutter：如何从谷歌地图中清除折线

Question

我用下面的代码创建了一个带有标记和折线的谷歌地图小部件。

一切正常，除了当我在两个坐标之间绘制一条折线，然后尝试删除它时，折线不会被删除（至少不是永久删除）。当我使用以下方法尝试删除旧折线并添加新折线时，我得到两条折线：

_polyLine.clear()
_polyLine.remove("id")
polylines.removeWhere((m) => m.polylineId.value == 'polyId$_randPolyId')

除了新的之外，它被删除然后再次添加。结果如下图：

...

void showPinsOnMap() {        
      // _polylines.removeWhere(
      // (m) => m.polylineId.value == 'polyId$_randPolyId');
      // _polylines.clear()
      _polylines = {};
      print("\n\n\nPolyLines Lenght: ${_polylines.length}\n\n\n");

   var pinPosition = LatLng(_currentLocation.latitude,_currentLocation.longitude);

   var destPosition = LatLng(_destinationLocation.latitude,
   _destinationLocation.longitude);
   _markers.add(Marker(
      markerId: MarkerId('sourcePin'),
      position: pinPosition,
      icon: _sourceIcon
   ));
   _markers.add(Marker(
      markerId: MarkerId('destPin'),
      position: destPosition,
      icon: _destinationIcon,
   ));

   setPolylines();
   notifyListeners();
}

...

...
void setPolylines() async {
   List<PointLatLng> result = await _polylinePoints.getRouteBetweenCoordinates(
   _googleAPIKey,
   _currentLocation.latitude,
   _currentLocation.longitude,
   _destinationLocation.latitude,
   _destinationLocation.longitude).catchError((onError){
     print("\n\n\n An Error Occured Possibly dure to network issues\n\n\n");
   });

  if(result != null){
    print("Results not null");
   if(result.isNotEmpty){
      result.forEach((PointLatLng point){
         _polylineCoordinates.add(
            LatLng(point.latitude,point.longitude)
         );
      });
       _isLoadingData = false;
      _polylines.add(Polyline(
        width: 5, 
        polylineId: PolylineId('polyId$_randPolyId'),
        color:
        Color.fromARGB(255, 40, 122, 198), 
        points: _polylineCoordinates
        ));
  }
  }
  notifyListeners();
}
...

Answer 1

您需要在绘制新路径之前清除 polylineCoordinates。

polylineCoordinates.clear(); // 在检查结果值之前调用它。

polylineCoordinates.clear();
    if(result != null){
    print("Results not null");
   if(result.isNotEmpty){
      result.forEach((PointLatLng point){
         _polylineCoordinates.add(
            LatLng(point.latitude,point.longitude)
         );
      });

  }
}