未处理的异常:即使给定了double,类型'String'也不是类型'double'的子类型

时间:2019-05-22 09:11:30

标签: dart flutter google-cloud-firestore

我正在从Firestore中获取坐标,以使用商店位置填充地图。 Google Map Marker需要一个LatLng对象(以两个double作为参数),该对象具有一个点的纬度和经度。但是,对于每个增量,我都会收到以下异常:type 'String' is not a subtype of type 'double'(在下面进行详细说明)。

但是,这些点确实出现在地图上,这意味着值的类型为double ...

我使用以下代码来识别纬度和经度类型:

if (store['latitude'] is double) {
  print('double!');
} else if (store['latitude'] is String) {
  print('string!');
}
print('');
if (store['longitude'] is double) {
  print('double!');
} else if (store['longitude'] is String) {
  print('string!');
}
print('');

它说“加倍!”每次。

代码如下:

Firestore.instance
        .collection('points-of-sale')
        .snapshots()
        .listen((data) => data.documents.forEach((store) {
              LatLng pos = LatLng(
                 store['latitude'], // Here
                 store['longitude'] // and here
              );
              /* Adding a marker to the map */
            }));

这是完整的错误:

[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: type 'String' is not a subtype of type 'double'
#0      _StoreLocatorState._addMarker (package:leonor_greyl_app_2019_41820/pages/StoreLocatorWidget.dart:21:30)
#1      _StoreLocatorState.build.<anonymous closure>.<anonymous closure> (package:leonor_greyl_app_2019_41820/pages/StoreLocatorWidget.dart:48:15)
#2      List.forEach (dart:core-patch/growable_array.dart:278:8)
#3      _StoreLocatorState.build.<anonymous closure> (package:leonor_greyl_app_2019_41820/pages/StoreLocatorWidget.dart:47:42)
#4      _rootRunUnary (dart:async/zone.dart:1132:38)
#5      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#6      _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#7      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#8      _DelayedData.perform (dart:async/stream_impl.dart:591:14)
#9      _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
#10     _PendingEvents.schedule.<anonymous closure> (dart:a<…>

编辑: 这是parseDouble(store['latitude'])的完整详细输出:

[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: FormatException: Invalid double
x
#0      double.parse (dart:core-patch/double_patch.dart:110:28)
#1      _StoreLocatorState._addMarker (package:leonor_greyl_app_2019_41820/pages/StoreLocatorWidget.dart:22:66)
#2      _StoreLocatorState.build.<anonymous closure>.<anonymous closure> (package:leonor_greyl_app_2019_41820/pages/StoreLocatorWidget.dart:51:15)
#3      List.forEach (dart:core-patch/growable_array.dart:278:8)
#4      _StoreLocatorState.build.<anonymous closure> (package:leonor_greyl_app_2019_41820/pages/StoreLocatorWidget.dart:50:42)
#5      _rootRunUnary (dart:async/zone.dart:1132:38)
#6      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#7      _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#8      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#9      _DelayedData.perform (dart:async/stream_impl.dart:591:14)
#10     _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
#11     _<…>

1 个答案:

答案 0 :(得分:0)

使用parseDouble函数,如果提供的Object无法解析为double,则该函数返回null。然后,您可以在创建标记之前检查经度和纬度的值是否为空。

  Firestore.instance
      .collection('points-of-sale')
      .snapshots()
      .listen((data) => data.documents.forEach((store) {
            double latitude = parseDouble(store['latitude']);
            double longitude = parseDouble(store['longitude']);

                // Check if parser returns null for non-parsable string
            if (latitude != null && longitude != null) {
              LatLng pos = LatLng(latitude, longitude);
              /* Adding a marker to the map */
            }
          }));

解析功能

double parseDouble(dynamic value) {
  try {
    if (value is String) {
      return double.parse(value);
    } else if (value is double) {
      return value;
    } else {
      return 0.0;
    }
  } catch (e) {
    // return null if double.parse fails
    return null;
  }
}