问题描述
我有一个应用程序，该应用程序从firebase读取停车数据并在地图上显示的一些图钉。现在，该应用程序仅显示用于停车的图钉，但我还想在地图上添加保存在“停车”集合的“批次”子集合中的每个停车场的图钉。我该怎么办？
maps.dart：
class StoreMap extends StatelessWidget {
StoreMap({
Key key,@required this.documents,@required this.initialPosition,}) : super(key: key);
final List<DocumentSnapshot> documents;
final LatLng initialPosition;
final Completer<GoogleMapController> _controller = Completer();
static final CameraPosition _initialPosition = CameraPosition(
target: LatLng(45.791789,24.150390),zoom: 16,);
@override
Widget build(BuildContext context) {
return Scaffold(
body: GoogleMap(
mapType: MapType.hybrid,initialCameraPosition: _initialPosition,onMapCreated: (GoogleMapController controller) {
_controller.complete(controller);
},myLocationEnabled: true,markers:documents.map((document) => new Marker(
markerId: MarkerId(document.get('name')),position: LatLng(
document.get('location').latitude,document.get('location').longitude,),onTap: () => _changeMap(LatLng(
document.get('location').latitude,)),infoWindow: InfoWindow(
title: document.get('name'),snippet: document.get('numberOfLots')),icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueViolet)),)
.toSet()
),floatingActionButton: FloatingActionButton(
onpressed: _currentLocation,child: Icon(Icons.location_searching),backgroundColor: Colors.deepPurple[400],);
}
解决方法
document.collection("lots").document("DocumentId").get('location').latitude不起作用的原因是，您不应该传递字段名称来获取方法。同样在您的代码中，文档只是文档快照，因此您要做的就是获取该文档的ID，然后访问其子集合和子文档。
您可以执行以下操作：
//The code below gets the document ids of the parking collection
//gets access the sub collection "lots" and gets all the documents inside it.
//and for every sub document,gets the data and prints the latitude of the location field
for (DocumentSnapshot document in documents){
String documentId = document.documentId;
DocumentReference parkingDocReference =
Firestore.instance.collection("Parkings").document(documentId);
parkingDocReference.collection("lots")
.get((QuerySnapshot subDocuments){
List<DocumentSnapshot> subDocumentsSnapshots = subDocuments.documents;
for (DocumentSnapshot subDoc in subDocumentsSnapshots){
String subDocId = subDoc.documentId;
parkingDocReference.collection("lots")
.document(subDocId).get().then((DocumentSnapshot snapshot){
print(snapshot.data["location"].latitude); //prints the latitude;
}
}
});
}
get（）将返回Future<DocumentSnapshot>，这就是我们在get（）之后使用.then（）的原因，以便该函数仅在检索到数据时运行
更新：
为了查看地图上的标记，我们将上面的代码放在返回Future<List<Marker>>的函数中。返回结果后，可以调用setState并使用小部件树中的更新列表。
最好使用async/await而不是then，因为它会强制程序首先从将来获取结果。
Future<List<Marker>> _createMarkersForLotsAndParkings() async{
List<Marker> markersList = [];
int markerId = 0;
for (DocumentSnapshot document in widget.documents){
// ignore: deprecated_member_use
String documentId = document.documentID;
DocumentReference parkingDocReference =
// ignore: deprecated_member_use
Firestore.instance.collection("Parkings").document(documentId);
DocumentSnapshot parkingDocRef = await parkingDocReference.get();
markersList.add(Marker(
markerId: MarkerId(markerId.toString()),position: LatLng(parkingDocRef.get('location').latitude,parkingDocRef.get('location').longitude),onTap: () => _changeMap(LatLng(
parkingDocRef.get('location').latitude,parkingDocRef.get('location').longitude)),infoWindow: InfoWindow(
title: document.get('name'),snippet: document.get('numberOfLots')),icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueYellow)),);
markerId++;
QuerySnapshot subDocuments = await parkingDocReference.collection("lots").get();
// ignore: deprecated_member_use
// ignore: deprecated_member_use
List<DocumentSnapshot> subDocumentsSnapshots = subDocuments.documents;
for (DocumentSnapshot subDoc in subDocumentsSnapshots){
// ignore: deprecated_member_use
String subDocId = subDoc.documentID;
DocumentSnapshot snapshot = await parkingDocReference.collection("lots")
// ignore: deprecated_member_use
.document(subDocId).get();
print(snapshot.get('location').latitude);
markersList.add(
Marker(
markerId:MarkerId(markerId.toString()),position: LatLng(snapshot.get('location').latitude,snapshot.get('location').longitude),onTap: () => _changeMap(LatLng(
snapshot.get('location').latitude,snapshot.get('location').longitude)),icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueViolet)),);
markerId++;
}
}
return Future.value(markersList);
}
我们在initState()中调用此函数。您需要将StoreMap转换为StatefullWidget才能调用setState并使用initState：
@override
void initState() {
super.initState();
_createMarkersForLots().then((List<Marker> lotsMarkers){
setState((){
markers = lotsMarkers; //rebuilds the screen with the lotsMarkers. make sure to use the markers in your widget tree to see the markers
});
});
}
您的完整代码必须看起来像这样：
import 'dart:async';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';
class StoreMap extends StatefulWidget {
StoreMap({
Key key,@required this.documents,@required this.initialPosition,}) : super(key: key);
final List<DocumentSnapshot> documents;
final LatLng initialPosition;
static final CameraPosition _initialPosition = CameraPosition(
target: LatLng(45.791789,24.150390),zoom: 16,);
@override
_StoreMapState createState() => _StoreMapState();
}
class _StoreMapState extends State<StoreMap> {
final Completer<GoogleMapController> _controller = Completer();
List<Marker> markers = [];
Future<List<Marker>> _createMarkersForLotsAndParkings() async{
List<Marker> markersList = [];
int markerId = 0;
for (DocumentSnapshot document in widget.documents){
// ignore: deprecated_member_use
String documentId = document.documentID;
DocumentReference parkingDocReference =
// ignore: deprecated_member_use
Firestore.instance.collection("Parkings").document(documentId);
DocumentSnapshot parkingDocRef = await parkingDocReference.get();
markersList.add(Marker(
markerId: MarkerId(markerId.toString()),);
markerId++;
}
}
return Future.value(markersList);
}
@override
void initState() {
super.initState();
_createMarkersForLotsAndParkings().then((List<Marker> lotsMarkers){
setState((){
markers = lotsMarkers;
});
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: GoogleMap(
zoomGesturesEnabled: true,mapType: MapType.hybrid,initialCameraPosition: StoreMap._initialPosition,onMapCreated: (GoogleMapController controller) {
_controller.complete(controller);
},myLocationEnabled: true,markers: markers.toSet(),),floatingActionButton: FloatingActionButton(
onPressed: _currentLocation,child: Icon(Icons.location_searching),backgroundColor: Colors.deepPurple[400],);
}
void _currentLocation() async {
final GoogleMapController controller = await _controller.future;
LocationData currentLocation;
var location = new Location();
try {
currentLocation = await location.getLocation();
} on Exception {
currentLocation = null;
}
controller.animateCamera(CameraUpdate.newCameraPosition(
CameraPosition(
bearing: 0,target: LatLng(currentLocation.latitude,currentLocation.longitude),zoom: 18.0,));
}
_changeMap(LatLng position) async {
final GoogleMapController controller = await _controller.future;
controller.animateCamera(CameraUpdate.newCameraPosition(
CameraPosition(
bearing: 0,target: LatLng(position.latitude,position.longitude),zoom: 19.4,));
}
}
Google地图为具有相同ID的标记显示一个标记，这就是为什么我们使用markerId为每个标记赋予唯一的ID并查看所有标记的原因。