dart - 导航到另一个屏幕时总是空白

Question

我正在尝试使用Navigator.push()从一个屏幕导航到另一个屏幕。我有一个GridView和任何GridTile的onTap我正在打开另一个屏幕。但是，即使有Scaffold，第二个屏幕也始终是空白的。联网 call 没有问题，因为来自网络的所有数据都已正确加载。我通过打印进行了验证。这是两个屏幕:

第一个画面:

import 'package:flutter/material.dart';
import '../models/item_model.dart';
import '../blocs/movies_bloc.dart';
import 'movie_detail.dart';

class MovieList extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return MovieListState();
  }
}

class MovieListState extends State<MovieList> {
  @override
  void initState() {
    super.initState();
    print("initState called");
    bloc.fetchAllMovies();
  }

  @override
  void dispose() {
    // TODO: implement dispose
    bloc.dispose();
    print("dispose called");
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text('Popular Movies'),
      ),
      body: StreamBuilder(
        stream: bloc.allMovies,
        builder: (context, AsyncSnapshot<ItemModel> snapshot) {
          if (snapshot.hasData) {
            return buildList(snapshot);
          } else if (snapshot.hasError) {
            return Text(snapshot.error.toString());
          }
          return Center(child: CircularProgressIndicator());
        },
      ),
    );
  }

  Widget buildList(AsyncSnapshot<ItemModel> snapshot) {
    return GridView.builder(
        itemCount: snapshot.data.results.length,
        gridDelegate:
            new SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
        itemBuilder: (BuildContext context, int index) {
          return GridTile(
            child: InkResponse(
              enableFeedback: true,
              child: Image.network(
                'https://image.tmdb.org/t/p/w185${snapshot.data
                    .results[index].poster_path}',
                fit: BoxFit.cover,
              ),
              onTap: () => openDetailPage(snapshot.data, index),
            ),
          );
        });
  }

  openDetailPage(ItemModel data, int index) {
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) {
        MovieDetail(
          title: data.results[index].title,
          posterUrl: data.results[index].poster_path,
          description: data.results[index].overview,
          releaseDate: data.results[index].release_date,
        );
      }),
    );
  }
}

第二屏:

import 'package:flutter/material.dart';

class MovieDetail extends StatelessWidget {
  final posterUrl;
  final description;
  final releaseDate;
  final String title;

  MovieDetail({Key key, this.title, this.posterUrl, this.description, this.releaseDate}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text('Movie Details'),
      ),
      body: Text(
        "Sample text",
        style: TextStyle(color: Colors.white),
      ),
    );
  }
}

这是怎么了？

Answer 1

MaterialPageRoute的生成器存在问题:它不返回任何内容。

添加一个return语句，应该没问题:

  MaterialPageRoute(builder: (context) {
    return MovieDetail(
      title: data.results[index].title,
      posterUrl: data.results[index].poster_path,
      description: data.results[index].overview,
      releaseDate: data.results[index].release_date,
    );
  }),