等待后的代码没有运行颤振

Question

我正在尝试调用一个函数，该函数将通过读取流来填充列表。意思是，它将读取一个流并将值添加到一个列表中，最后，该列表将由函数返回。

问题是，当我使用 await for 读取流时，await for 之后的代码没有被执行。而且我尝试使用听，然后它不会等待完成阅读流。甚至在流被完全读取之前，监听之后的代码就已经被执行了。

按照我的代码-

Future<List<Map<String, dynamic>>> getNearestDriver(Stream<List<DocumentSnapshot>> driverWithinRangeStream, GeoPoint source) async {
    print("Get Nearest Driver Called");
    List<Map<String, dynamic>> driverAvailableList = [];
    await for (List<DocumentSnapshot> documentList in driverWithinRangeStream){
      documentList.forEach((DocumentSnapshot document) async {
        String driverIDVar = document.data['driverid'];
        GeoPoint pos = document.data['position']['geopoint'];
        var point = geo.point(latitude: pos.latitude, longitude: pos.longitude);
        double distanceVar = point.distance(lat: source.latitude, lng: source.longitude);
        int distanceInMeter = (distanceVar*1000).round();
        Map<String, dynamic> newDriverAvailable = {"driverId": driverIDVar, "distance" : distanceInMeter};
        driverAvailableList.add(newDriverAvailable);
      });
      print(driverAvailableList); /* <- I get the data here */
    }
    print(driverAvailableList); /* <- But I don't get the data here. This code is not even being executed. */
  }

请告诉我这里出了什么问题。

Answer 1

你想试试

try{
    await for (List<DocumentSnapshot> documentList in driverWithinRangeStream){
        await Future.forEach(documentList, (DocumentSnapshot document) async {
           try{     
                String driverIDVar = document.data['driverid'];
                GeoPoint pos = document.data['position']['geopoint'];
                var point = geo.point(latitude: pos.latitude, longitude: pos.longitude);
                double distanceVar = point.distance(lat: source.latitude, lng: source.longitude);
                int distanceInMeter = (distanceVar*1000).round();
                Map<String, dynamic> newDriverAvailable = {"driverId": driverIDVar, "distance" : distanceInMeter};
                driverAvailableList.add(newDriverAvailable);
           }catch(error){
                throw "throw from documentList, Error:$error";}
        });
    }
 }catch(error){
     print ("catch in driverWithinRangeStream, Error:$error");}