在flutter中为手机和网络使用谷歌地图

Question

我正在开发一个颤动应用程序，它应该有一个通用的Web和移动设备代码库。

我的应用程序将有一个谷歌地图，据我所知，没有一个软件包可以满足所有平台。

google_maps_flutter - seems to work only for mobile (IOS / Android)
google_maps_flutter_web - seems to work only for web

所以很可能我必须使用这些独立的包创建两个独立的MapWidgets，一个用于web，一个用于移动。

对于移动设备:

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

class MapSample extends StatefulWidget {
  MapSample({Key? key}) : super(key: key);

  @override
  State<MapSample> createState() => MapSampleState();
}

class MapSampleState extends State<MapSample> {
  final Completer<GoogleMapController> _controller = Completer();

  static const CameraPosition _kGooglePlex = CameraPosition(
    target: LatLng(37.42796133580664, -122.085749655962),
    zoom: 14.4746,
  );

  @override
  Widget build(BuildContext context) {
    return GoogleMap(
      mapType: MapType.hybrid,
      initialCameraPosition: _kGooglePlex,
      onMapCreated: (GoogleMapController controller) {
        _controller.complete(controller);
      },
    );
  }
}

对于web来说，它有点复杂，看起来google_maps_flutter_web实际上不是一个可用的版本，据我所知，（如果我错了请纠正我），它实际上使用了另一个不是由flutter团队开发的包google_maps6.0.0。

google_maps_flutter_web的目标可能是拥有与google_maps_flutter（google_maps_flutter_platform_interface）相同的api并无缝使用它，但我真的找不到如何使用它的示例...

我应该怎么做？我对google_maps_flutter_web的任何改变都是错误的，它实际上是有效的？或者我应该尝试使用实际上适用于Web的google_maps，然后根据kIsWeb切换小部件？

Answer 1

编辑：一个新的官方插件已经发布：https://pub.dev/packages/google_maps_flutter_web。它已经可以与现有的google_maps_flutter插件一起使用，只需在 web/index.html 中添加您的api脚本即可。

正如用户exilonX建议的那样，目前(2012年4月)在Flutter web和移动设备上使用谷歌地图的方式是基于设备动态加载库。然而，他的回答缺少一些重要的细节。我花了将近一个小时来完成他的工作，因此我在这里分享了一个更清晰、更有条理的解决方案，希望能节省你一些时间(由于编辑队列太长，我无法编辑他的答案)。

文件夹结构：

\widget
   \map_widget.dart
   \web_map_widget.dart
   \mob_map_widget.dart
   \map_widget_stub.dart

地图小部件:

在文件map_widget.dart中，您将拥有抽象的MapWidget：

import 'package:flutter/material.dart';

import 'map_widget_stub.dart'
    if (dart.library.html) 'web_map_widget.dart'
    if (dart.library.io) 'mob_map_widget.dart';

abstract class MapWidget extends StatefulWidget {
  factory MapWidget() => getMapWidget();
}

注意:您在条件导入中唯一需要的半列在第二个if的末尾。

Web MapWidget：

该文件将包含web上显示的谷歌地图：

import 'dart:html';
import 'dart:ui' as ui;

import 'package:flutter/material.dart';
import 'package:google_maps/google_maps.dart';

import 'map_widget.dart';

MapWidget getMapWidget() => WebMap();

class WebMap extends StatefulWidget implements MapWidget {
  WebMap({Key? key}) : super(key: key);

  @override
  State<WebMap> createState() => WebMapState();
}

class WebMapState extends State<WebMap> {
  @override
  Widget build(BuildContext context) {
    final String htmlId = "map";

    // ignore: undefined_prefixed_name
    ui.platformViewRegistry.registerViewFactory(htmlId, (int viewId) {
      final mapOptions = MapOptions()
        ..zoom = 15.0
        ..center = LatLng(35.7560423, 139.7803552);

      final elem = DivElement()..id = htmlId;
      final map = GMap(elem, mapOptions);

      map.onCenterChanged.listen((event) {});
      map.onDragstart.listen((event) {});
      map.onDragend.listen((event) {});

      Marker(MarkerOptions()
        ..position = map.center
        ..map = map);

      return elem;
    });
    return HtmlElementView(viewType: htmlId);
  }
}

在这里您可以找到有关web实现的更多详细信息。

移动地图小工具：

此文件包含移动设备(android/ios)的实现:

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

import 'map_widget.dart';

MapWidget getMapWidget() => MobileMap();

class MobileMap extends StatefulWidget implements MapWidget {
  MobileMap({Key? key}) : super(key: key);

  @override
  State<MobileMap> createState() => MobileMapState();
}

class MobileMapState extends State<MobileMap> {
  final Completer<GoogleMapController> _controller = Completer();

  static const CameraPosition _kFalentexHouse =
      CameraPosition(target: LatLng(44.497858579692135, 11.336362079086408));

  @override
  Widget build(BuildContext context) {
    return GoogleMap(
      mapType: MapType.hybrid,
      initialCameraPosition: _kFalentexHouse,
      onMapCreated: (GoogleMapController controller) {
        _controller.complete(controller);
      },
    );
  }
}

烟蒂

最后，您需要一个存根：

import 'map_widget.dart';

//the error is shown in case of wrong version loaded on wrong platform
MapWidget getMapWidget() => throw UnsupportedError(
    'Cannot create a map without dart:html or google_maps_flutter');

用法

现在您可以将小部件MapWidget用作普通小部件：

Scaffold(
      body: Center(
        child: SizedBox(
          height: 300,
          width: 300,
          child: MapWidget(),
        ),
      ),
    );

注意：为了使地图工作，您需要使用键进行设置。请参阅移动和网络的官方图书馆文档。

Answer 2

最终，我使用< code>google_maps和这个答案作为灵感找到了一个变通方法:

1. 抽象MapWidget

    import 'package:client_ojp4danube/map/map_widget_stub.dart'
        if (dart.library.html) 'package:client_ojp4danube/map/map_web_widget.dart'
        if (dart.library.io) 'package:client_ojp4danube/map/map_widget.dart';
    
    import 'package:flutter/material.dart';
    
    abstract class MapWidget extends StatefulWidget {
      factory MapWidget() => getMapWidget();
    }

    import 'dart:html';
    
    import 'package:client_ojp4danube/map/abstract_map_widget.dart';
    import 'package:flutter/cupertino.dart';
    import 'package:google_maps/google_maps.dart';
    import 'dart:ui' as ui;
    
    Widget getMap() {
      String htmlId = "7";
    
      // ignore: undefined_prefixed_name
      ui.platformViewRegistry.registerViewFactory(htmlId, (int viewId) {
        final myLatlng = new LatLng(30.2669444, -97.7427778);
    
        final mapOptions = new MapOptions()
          ..zoom = 8
          ..center = new LatLng(30.2669444, -97.7427778);
    
        final elem = DivElement()
          ..id = htmlId
          ..style.width = "100%"
          ..style.height = "100%"
          ..style.border = 'none';
    
        final map = GMap(elem, mapOptions);
    
        Marker(MarkerOptions()
          ..position = myLatlng
          ..map = map
          ..title = 'Hello World!');
    
        return elem;
      });
    
      return HtmlElementView(viewType: htmlId);
    }
    
    class WebMap extends StatefulWidget implements MapWidget {
      WebMap({Key? key}) : super(key: key);
    
      @override
      State<WebMap> createState() => WebMapState();
    }
    
    class WebMapState extends State<WebMap> {
      @override
      Widget build(BuildContext context) {
        return getMap();
      }
    }
    
    MapWidget getMapWidget() {
      print("Intra in get map web ");
      return WebMap();
    }

    import 'dart:async';
    
    import 'package:client_ojp4danube/map/abstract_map_widget.dart';
    import 'package:flutter/material.dart';
    import 'package:google_maps_flutter/google_maps_flutter.dart';
    
    class MobileMap extends StatefulWidget implements MapWidget {
      MobileMap({Key? key}) : super(key: key);
    
      @override
      State<MobileMap> createState() => MobileMapState();
    }
    
    class MobileMapState extends State<MobileMap> {
      final Completer<GoogleMapController> _controller = Completer();
    
      static const CameraPosition _kGooglePlex = CameraPosition(
        target: LatLng(37.42796133580664, -122.085749655962),
        zoom: 14.4746,
      );
    
      @override
      Widget build(BuildContext context) {
        return GoogleMap(
          mapType: MapType.hybrid,
          initialCameraPosition: _kGooglePlex,
          onMapCreated: (GoogleMapController controller) {
            _controller.complete(controller);
          },
        );
      }
    }
    
    MapWidget getMapWidget() {
      return MobileMap();
    }

    import 'package:client_ojp4danube/map/abstract_map_widget.dart';
    
    // Created because importing dart.html on a mobile app breaks the build
    MapWidget getMapWidget() => throw UnsupportedError(
        'Cannot create a map without dart:html or google_maps_flutter');

import 'package:client_ojp4danube/map/abstract_map_widget.dart';


class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(child: MapWidget()),
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}