loops - 无法在 Flutter 中过滤位置

Question

我正在尝试过滤掉我的 flutter 应用程序中的位置。我可以过滤我的标记，但我不确定按名称详细信息提取位置的最佳方法是什么。以下是我创建标记的方式:

  Map<MarkerId, Marker> markers = <MarkerId, Marker>{};


  Future filterMarker(_userlat, _userlong) async {
    int filterCounter = 0;

    for (int i = 0; i < venues.length; ++i) {
      Geolocator()
          .distanceBetween(
              _userLat, _userlong, venues[i].latitude, venues[i].longitude)
          .then((calcDist) {
        if (calcDist / 1000 < 1) {
          filterCounter++;
          placeFilteredMarker(filterCounter, calcDist / 1000, venues[i].name,
              venues[i].latitude, venues[i].longitude);

          filtervenues(filterCounter, venues[i].name, venues[i].address,
              venues[i].rating, calcDist / 1000);
        }
      });
    }
  }


  placeFilteredMarker(counter, distance, name, lat, lng) {
    final int markerCount = counter;

    for (int i = 0; i < markerCount; i++) {
      final String markerIdVal = 'marker_id_$markerCount';

      final MarkerId markerId = MarkerId(markerIdVal);

      // creating a new MARKER
      final Marker marker = Marker(
        markerId: markerId,
        position: LatLng(lat, lng),
        infoWindow: InfoWindow(title: name, snippet: '$distance'),
        icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueBlue),
      );

      setState(() {
        markers[markerId] = marker;
        // adding a new marker to map
      });

      return;
    }
  }

我正在尝试使用详细信息列表进行类似操作。按位置过滤并显示详细信息，但我不明白我做错了什么。这是我正在尝试的

问题是:我不确定我应该怎么做才能提取姓名、地址和评级。

List<Venue>venue;  
  
  Future filterMarker(_userlat, _userlong) async {
    int filterCounter = 0;

    for (int i = 0; i < venues.length; ++i) {
      Geolocator()
          .distanceBetween(
              _userLat, _userlong, venues[i].latitude, venues[i].longitude)
          .then((calcDist) {
        if (calcDist / 1000 < 1) {
          filterCounter++;
          placeFilteredMarker(filterCounter, calcDist / 1000, venues[i].name,
              venues[i].latitude, venues[i].longitude);

          filtervenues(filterCounter, venues[i].name, venues[i].address,
              venues[i].rating, calcDist / 1000);
        }
      });
    }
  }
  
  
  filtervenues(counter, name, addres, rating, distance) {
    final int venueCounter = counter;
    
    for (int i = 0; i < venueCounter; i++) {
      setState(() {


      });
      return;
    }
  }

那应该迭代然后添加到下面的容器中:

  Widget _buildList(BuildContext context, _name, _address, _rating) {
  
    return Container(
      height: 425,
      child: Column(
              children: <Widget>[
                SizedBox(
                  height: 2,
                ),
                SizedBox(
                  height: 2,
                ),
                _locations(venues[index].name, venues[index].address,
                    venues[index].rating),
                Divider(
                  height: 2,
                )
              ],
            );
          ),
    );
  }

照片更新。我正在尝试将标记的数据放入此底页。

Answer 1

首先:这整个逻辑似乎表现不佳。您在 for 循环的每次迭代中设置 State，这会导致 MapsWidget 重建每次迭代。你为什么不创建一个标记项列表，然后最后像下面的代码那样做呢？另外我会做类似于 field 的事情:

class Location {
   final Venue venue;
   final double dist;
   final int index;
   Location({this.venue, this.dist, this.index});
}

  Set<Marker> markers = Set(); //Google Maps Markers are normally a Set
  List<Location> location = List();


  Future filterMarker(_userlat, _userlong) async {
    Set<Marker> _tmpMarkers = Set();
    int filterCounter = 0;
    List<Location> _tmpLocation = List();
    for (int i = 0; i < venues.length; ++i) {
      Geolocator()
          .distanceBetween(
              _userLat, _userlong, venues[i].latitude, venues[i].longitude)
          .then((calcDist) {
        if (calcDist / 1000 < 1) {
          filterCounter++;
          final String markerIdVal = 'marker_id_$filterCounter';

          final MarkerId markerId = MarkerId(markerIdVal);

         // creating a new MARKER
         tmpMarkers.add(Marker(
           markerId: markerId,
           position: LatLng(venues[i].latitude, venues[i].longitude),
           infoWindow: InfoWindow(title: venues[i].name, snippet: '$calcDist / 1000'),
           icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueBlue),
          ));
          _tmpLocation.add(Location(index: i, Venue: venue[i], dist: calcDist / 1000));
        }
      });
    }
    setState((){
     markers = _tmpMarkers;
     location = _tmpLocation;
    });
  }

然后您在底部工作表中使用您的位置对象。此外，我无法测试此代码，因为我没有您的完整代码，可能缺少一些括号。

然后您可以在 bottomSheet 的 ListView.builder 中使用位置列表。在那里，您可以自己设置每个列表磁贴的样式。

// As you didn't provide any code of your bottom sheet i just call it DraggableBottomSheet
bottomSheet: DraggableBottomSheet(
   child: Column(
    children : [
      Row(
        children: [
           Text('bla'),
           Text(location.length.toString(),
             ]
        ),
      ListView.builder(
          itemCount: location.length,
          itemBuilder: (context, index) {
             return Container(
                 child Column(
                     children : [
                          Text(location[index].venue.name),
                          Text(location[index].dist.toString()),
                       ]
                 )
              );
            }
        )
     ]
   )
)