错误：“使用不包含导航器的上下文请求导航器操作。”

痛了好久，不知道怎么解决。应用程序启动，但是理论上，当您单击 gridView 元素时，应该会显示一个带有图片的窗口，但是当您单击它时，它会显示错误异常捕获的手势“Navigator operation requested with a context that does not包括一个导航器。”

主要.dart

import 'package:flutter/material.dart';
import 'details.dart';
import 'services.dart';
import 'album.dart';
import 'cell.dart';
import 'dart:async';

void main()=>runApp(GridViewDemo());

class GridViewDemo extends StatefulWidget {

  final String title = "Photos";

  @override
  GridViewDemoState createState() => GridViewDemoState();

}

class GridViewDemoState extends State<GridViewDemo> {
  //
  StreamController<int> streamController = new StreamController<int>();

  gridview(AsyncSnapshot<List<Album>> snapshot) {
      return Padding(
        padding: EdgeInsets.all(5.0),
        child: GridView.count(
          crossAxisCount: 2,
          childAspectRatio: 1.0,
          mainAxisSpacing: 4.0,
          crossAxisSpacing: 4.0,
          children: snapshot.data.map(
                (album) {
              return GestureDetector(
                child: GridTile(
                  child: AlbumCell(album),
                ),
                onTap: () {
                 goToDetailsPage(context, album);
                },
              );
            },
          ).toList(),
        ),

      );
  }

  goToDetailsPage(BuildContext context, Album album) {
    Navigator.push(
      context,
      MaterialPageRoute(
        fullscreenDialog: true,
        builder: (BuildContext context) => GridDetails(
          curAlbum: album,
        ),
      ),
    );

  }


  circularProgress() {
    return Center(
      child: const CircularProgressIndicator(),
    );
  }


  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: StreamBuilder(
            initialData: 0,
            stream: streamController.stream,
            builder: (BuildContext context, AsyncSnapshot snapshot) {
              return Text('${widget.title} ${snapshot.data}');
            },
          )),
       body: Column(
        mainAxisAlignment: MainAxisAlignment.start,
        crossAxisAlignment: CrossAxisAlignment.start,
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          Flexible(
            child: FutureBuilder<List<Album>>(
              future: Services.getPhotos(),
              builder: (context, snapshot) {
                // not setstate here
                //
                if (snapshot.hasError) {
                  return Text('Error ${snapshot.error}');
                }
                //
                if (snapshot.hasData) {
                  streamController.sink.add(snapshot.data.length);
                  // gridview
                  return gridview(snapshot);
                }

                return circularProgress();
              },
            ),
          ),
        ],
      ),
    ),
    );
  }

  @override
  void dispose() {
    streamController.close();
    super.dispose();
  }
}

细胞飞镖

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

class AlbumCell extends StatelessWidget {
  const AlbumCell(this.album);
  @required
  final Album album;

  @override
  Widget build(BuildContext context) {
    return Card(
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(10.0),
      ),
      color: Colors.white,
      child: Padding(
        padding: EdgeInsets.all(10.0),
        child: Container(
          alignment: Alignment.center,
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              Flexible(
                child: ClipRRect(
                  borderRadius: BorderRadius.circular(10.0),
                  child: Hero(
                    tag: "image${album.id}",
                    child: FadeInImage.assetNetwork(
                      placeholder: "images/no_image.png",
                      image: album.thumbnailUrl,
                      width: 100,
                      height: 100,
                    ),
                  ),
                ),
              ),
              Padding(
                padding: EdgeInsets.all(10.0),
                child: Text(
                  album.title,
                  maxLines: 1,
                  softWrap: true,
                  textAlign: TextAlign.center,
                  style: TextStyle(
                    fontSize: 20.0,
                    fontWeight: FontWeight.w500,
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

专辑.dart

class Album {


int albumId;
  int id;
  String title;
  String url;
  String thumbnailUrl;

  Album({this.albumId, this.id, this.title, this.url, this.thumbnailUrl});

  factory Album.fromJson(Map<String, dynamic> json) {
    return Album(
      albumId: json['albumId'] as int,
      id: json['id'] as int,
      title: json['title'] as String,
      url: json['url'] as String,
      thumbnailUrl: json['thumbnailUrl'] as String,
    );
  }
}

服务.dart

    import 'dart:convert';
import 'package:http/http.dart' as http;
import 'album.dart';

class Services {
  static const String url = "https://jsonplaceholder.typicode.com/photos";

  static Future<List<Album>> getPhotos() async {
    try {
      http.Response response = await http.get(
        Uri.encodeFull(url)
      );
      if (response.statusCode == 200) {
        List<Album> list = parsePhotos(response.body);
        return list;
      } else {
        throw Exception("Error");
      }
    } catch (e) {
      throw Exception(e.toString());
    }
  }

  static List<Album> parsePhotos(String responseBody) {
    final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();
    return parsed.map<Album>((json) => Album.fromJson(json)).toList();
  }
}

细节.dart

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

class GridDetails extends StatefulWidget {
  final Album curAlbum;
  GridDetails({@required this.curAlbum});

  @override
  GridDetailsState createState() => GridDetailsState();
}

class GridDetailsState extends State<GridDetails> {
  //
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        alignment: Alignment.center,
        margin: EdgeInsets.all(30.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.center,
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Hero(
              tag: "image${widget.curAlbum.id}",
              child: FadeInImage.assetNetwork(
                placeholder: "images/no_image.png",
                image: widget.curAlbum.url,
              ),
            ),
            SizedBox(
              height: 30.0,
            ),
            OutlineButton(
              child: Icon(Icons.close),
              onPressed: () => Navigator.of(context).pop(),
            ),
          ],
        ),
      ),
    );
  }
}