如何将列表转换为 Map 以获得必要的值？

Question

我正在使用一个 geocoding: ^2.0.4 插件，它根据坐标给我一个地址列表，我想要的只是街道名称和分区

这是打印结果的代码

List<Placemark> placemarks = await placemarkFromCoordinates(
              pointManual2!.latitude, pointManual2!.longitude);
          print(placemarks);

这是输出

I/flutter ( 4451): [      Name: Kathmandu,
I/flutter ( 4451):       Street: BHIMSENGOLA 32,
I/flutter ( 4451):       ISO Country Code: NP,
I/flutter ( 4451):       Country: Nepal,
I/flutter ( 4451):       Postal code: 44600,
I/flutter ( 4451):       Administrative area: Bagmati Province,
I/flutter ( 4451):       Subadministrative area: Kathmandu,
I/flutter ( 4451):       Locality: Kathmandu,
I/flutter ( 4451):       Sublocality: New Baneshwor,
I/flutter ( 4451):       Thoroughfare: ,
I/flutter ( 4451):       Subthoroughfare: ,       Name: Sinamangal Road,
I/flutter ( 4451):       Street: Sinamangal Rd,
I/flutter ( 4451):       ISO Country Code: NP,
I/flutter ( 4451):       Country: Nepal,
I/flutter ( 4451):       Postal code: 44600,
I/flutter ( 4451):       Administrative area: Bagmati Province,
I/flutter ( 4451):       Subadministrative area: Kathmandu,
I/flutter ( 4451):       Locality: Kathmandu,
I/flutter ( 4451):       Sublocality: New Baneshwor,
I/flutter ( 4451):       Thoroughfare: Sinamangal Road,
I/flutter ( 4451):       Subthoroughfare: ,       Name: Bhimsengola,
I/flutter ( 4451):       Street: Bhimsengola,
I/flutter ( 4451):       ISO Country Code: NP,
I/flutter ( 4451):       Country: Nepal,
I/flutter ( 4451):       Postal code: 44600,
I/flutter ( 4451):       Administrative area: Bagmati Province,
I/flutter ( 4451):       Subadministrative area: Kathmandu,
I/flutter ( 4451):       Locality: Kathmandu,
I/flutter ( 4451):       Sublocality: New Baneshwor,
I/flutter ( 4451):       Thoroughfare: ,
I/flutter ( 4451):       Subthoroughfare: ,       Name: New

我试过的

List<Placemark> placemarks = await placemarkFromCoordinates(
              pointManual2!.latitude, pointManual2!.longitude);
          print(placemarks);
var data = placemarks as Map?;
          String name = data?["Sublocality"];
          print("sublocality " + name);

错误

[ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: type 'List<Placemark>' is not a subtype of type 'Map<dynamic, dynamic>?' in type cast

我需要将其转换为地图吗？如果要我怎么办？

Answer 1

尽管我发现您的数据不正确，因为它不是声明变量时给出的 List<Placemark> 类型。

但是，要获得像 Sublocality 这样的 Placemark 的属性，您应该在列表的索引中访问该地标。

所以，对于第0项，如你的情况，感觉只有一项，用这个：

List<Placemark> placemarks = await placemarkFromCoordinates(
              pointManual2!.latitude, pointManual2!.longitude);
          print(placemarks);
Placemark placemark = placemarks[0];
//Because Placemark is a model class, properties like sublocality should be accessible
//using Dot (.) operator, you can check by erasing this .sublocality 
//and then type . to see the suggestions
String name = placemark.sublocality;

如何将列表转换为 Map 以获得必要的值？

How to convert a list to Map to get the necessary values?

dart

flutter