google-maps - 修复中心的谷歌地图标记

Question

在我的 flutter 应用中。我正在使用 google_maps_plugin 。链接是https://github.com/flutter/plugins/tree/master/packages/google_maps_flutter . 我想在拖动 map 后将标记固定在 map 中心而不移动。 我想要它喜欢http://jsfiddle.net/UuDA6/ 在我的代码中，我使用 MarkerOption 来放置标记。

    MarkerOptions options = new MarkerOptions(   
        alpha: 1.0,
        anchor: Offset(0.5, 1.0),
        consumeTapEvents: false,
        draggable: false,
        flat: false,
        icon: BitmapDescriptor.defaultMarker,
        infoWindowAnchor: Offset(0.5, 0.0),
        infoWindowText: InfoWindowText.noText,
        position: LatLng(17.411439, 78.5486697),
        rotation: 0.0,
        visible: true,
        zIndex: 0.0,
    );

但是在位置我想知道如何给出 map 的中心。

如果有人对此有任何想法，请分享。

Answer 1

实际上随着 google_maps_flutter: ^0.4.0 的新更新我们可以轻松实现上述要求。

这是演示 link .

Map<MarkerId, Marker> _markers = <MarkerId, Marker>{};
int _markerIdCounter = 0;
Completer<GoogleMapController> _mapController = Completer();

Container(
    width: MediaQuery.of(context).size.width,
    height: MediaQuery.of(context).size.height,
    child: GoogleMap(
      markers: Set<Marker>.of(_markers.values),
      onMapCreated: _onMapCreated,
      initialCameraPosition: CameraPosition(
        target: Constants.LOCATION_SRI_LANKA,
        zoom: 12.0,
      ),
      myLocationEnabled: true,
      onCameraMove: (CameraPosition position) {
        if(_markers.length > 0) {
          MarkerId markerId = MarkerId(_markerIdVal());
          Marker marker = _markers[markerId];
          Marker updatedMarker = marker.copyWith(
            positionParam: position.target,
          );

          setState(() {
            _markers[markerId] = updatedMarker;
          });
        }
      },
    ),
  )

void _onMapCreated(GoogleMapController controller) async {
  _mapController.complete(controller);
  if ([INITIAL_LOCATION] != null) {
    MarkerId markerId = MarkerId(_markerIdVal());
    LatLng position = [INITIAL_LOCATION];
    Marker marker = Marker(
      markerId: markerId,
      position: position,
      draggable: false,
    );
    setState(() {
      _markers[markerId] = marker;
    });

    Future.delayed(Duration(seconds: 1), () async {
      GoogleMapController controller = await _mapController.future;
      controller.animateCamera(
        CameraUpdate.newCameraPosition(
          CameraPosition(
            target: position,
            zoom: 17.0,
          ),
        ),
      );
    });
  }
}

String _markerIdVal({bool increment = false}) {
  String val = 'marker_id_$_markerIdCounter';
  if (increment) _markerIdCounter++;
  return val;
}