Flutter：将新值传递给 Stateful 小部件并更新视图 onTap

Question

我已经实现了google_maps_fltuter，每当用户点击边框内任意位置的不同路线时，我需要用新坐标更新地图上的路线（见下图）。最初渲染视图时，地图会安装第一条路线的坐标，但我还需要能够显示不同的路线。

我有一个 GestureDetector 小部件来允许这种情况发生，但它不会触发 RouteMap 类。

class _PlanJourney extends State<PlanJourney> {

...
  GestureDetector(
    onTap: () => RouteMap(from, to, routeCoordinates, i),
    child: Container(...)
  )
...

}

这是根据传递给类的坐标创建地图的类。

class RouteMap extends StatefulWidget {
  final fromCoordinate;
  final toCoordinate;
  final routeCoordinates;
  final routeIndex;

  RouteMap(this.fromCoordinate, this.toCoordinate, this.routeCoordinates, this.routeIndex);

  @override
  _RouteMap createState() => _RouteMap(fromCoordinate, toCoordinate, routeCoordinates, routeIndex);
}

class _RouteMap extends State<RouteMap> {
  final fromCoordinate;
  final toCoordinate;
  final routeCoordinates;
  final routeIndex;

  _RouteMap(this.fromCoordinate, this.toCoordinate, this.routeCoordinates, this.routeIndex);
  
  Completer<GoogleMapController> _controller = Completer();
  GoogleMapController mapController;

  LatLng _setCenter() {
    return LatLng(double.parse(this.toCoordinate.split(',').toList()[1]), 
    double.parse(this.toCoordinate.split(',').toList()[0]));
  }

  final Set<Marker> _markers = {};
  Map<PolylineId, Polyline> _mapPolylines = {};
  int _polylineIdCounter = 1;

  void _onMapCreated(GoogleMapController controller) {
    _setCenter();

    mapController = controller;
    _controller.complete(controller);
  
    // the coordinates coming from the API are in LonLat format
    // Google map only accepts LatLon format so we have to swap the around
    LatLng latLng_1 = LatLng(double.parse(this.fromCoordinate.split(',').toList()[1]), 
    double.parse(this.fromCoordinate.split(',').toList()[0]));
    LatLng latLng_2 = LatLng(double.parse(this.toCoordinate.split(',').toList()[1]), 
    double.parse(this.toCoordinate.split(',').toList()[0]));

    setState(() {
      _markers.clear();
      addMarker(latLng_1, "Title", "description");
      addMarker(latLng_2, "Title", "description");
    });
    
    _add(routeIndex);

  }
...

更新

我稍微更改了代码，但问题仍然存在。 SetState 更新了我需要发送到 RouteMap 类的值，但类本身没有更新。

class _PlanJourney extends State<PlanJourney> {

...
  GestureDetector(
    onTap: () {
      setState(() {
        routeIndex = i; // this is the value I need to send to RouteMap class
        // print(routeIndex) -> the routeIndex changes
      });
  },
    child: Container(...) // *note the map is not in this container
  )
...

}

...
// the map is initially created here
  Container(
    margin: EdgeInsets.only(bottom: 10),
    height: 400,
    child: RouteMap(widget.from, widget.to, routeCoordinates[routeIndex], journeyData['routes'][routeIndex])
  )
...

...
class RouteMap extends StatefulWidget {
  final fromCoordinate;
  final toCoordinate;
  final routeCoordinates;
  final routeIndex;

  RouteMap(this.fromCoordinate, this.toCoordinate, this.routeCoordinates, this.routeIndex);

  @override
  _RouteMap createState() => _RouteMap();
}

class _RouteMap extends State<RouteMap> {
  Completer<GoogleMapController> _controller = Completer();
  GoogleMapController mapController;
  final Set<Marker> _markers = {};
  Map<PolylineId, Polyline> _mapPolylines = {};
  int _polylineIdCounter = 1;

...
}
  
...

Answer 1

在 onTap() 中，您可以更新选定的值，如下所示：

GestureDetector(
    onTap: () => setState(() {
      selectedFrom = from;
      selectedTo = to;
      selectedRuteCoordinates = routeCoordinates;
    }),
    child: Container(
      child: RouteMap(from, to, routeCoordinates, i),
    )
)