值类型double不能分配给值类型Double，

Question

我的工作是逆向地理编码，试图用地址模型来存储用户数据。但是得到了这个错误。我试着加上"?“在model类中声明变量时签名，但它会引发异常。

地址类代码：

class Address{
  String? placeFormattedAddress; 
  String? placeName;
  String? placeId;
  Double lattitude;
  Double longitude;

  Address({this.placeFormattedAddress, this.lattitude, this.longitude, this.placeId, this.placeName});
}

出现问题的代码：

类placeSearcherMethods{静态未来searchCoodinateAddress(位置、上下文)异步{ String placeAddress = ""；

var response = await placeSearcher.getRequest(url);
if (response != "Failed!!"){
  placeAddress = response["results"][0]["formatted_address"];


  Address userPickUpAddress = new Address();
  userPickUpAddress.lattitude = position.latitude;
  userPickUpAddress.longitude = position.longitude;

  userPickUpAddress.placeName = placeAddress;


  Provider.of<carpool_data>(context, listen: false).update_pickup_location_address(userPickUpAddress);

  

}
return placeAddress;

}}

​

​

Answer 1

使用双类double? lattitude;

class Address {
  String? placeFormattedAddress;
  String? placeName;
  String? placeId;
  double? lattitude;
  double? longitude;

  Address(
      {this.placeFormattedAddress,
      this.lattitude,
      this.longitude,
      this.placeId,
      this.placeName});
}

并删除import 'dart:ffi';

Answer 2

双应小写

 double lattitude;
 double longitude;