dart - Flutter 如何将数据列表保存到本地存储

Question

我正在 flutter 上开发电影发现应用程序，我需要将正在播放的电影列表保存在本地存储中以供离线使用，那么我该怎么做 future > getNowPlayingMovies() 异步{ 最终字符串 nowPlaying = ' https://api.themoviedb.org/3/tv/airing_today?api_key= ' + '$myapikey' + '&page=' + '1';

var httpClient = new HttpClient();
try {
  // Make the call
  var request = await httpClient.getUrl(Uri.parse(nowPlaying));
  var response = await request.close();
  if (response.statusCode == HttpStatus.OK) {
    var jsonResponse = await response.transform(utf8.decoder).join();
    // Decode the json response
    var data = jsonDecode(jsonResponse);
    // Get the result list
    List results = data["results"];
    print(results);
    // Get the Movie list
    List<moviemodel> movieList = createNowPlayingMovieList(results);
    // Print the results.
    return movieList;
  } else {
    print("Failed http call.");
  }
} catch (exception) {
  print(exception.toString());
}
return null;}



  List<moviemodel> createNowPlayingMovieList(List data) {
List<Searchmodel> list = new List();
for (int i = 0; i < data.length; i++) {
  var id = data[i]["id"];
  String title = data[i]["name"];
  String posterPath = data[i]["poster_path"];
  String mediatype = data[i]["media_type"];

  moviemodel movie = new moviemodel(id, title, posterPath, mediatype);
  list.add(movie);
}
return list; }



List<Widget> createNowPlayingMovieCardItem(
  List<moviemodel> movies, BuildContext context) {
// Children list for the list.
List<Widget> listElementWidgetList = new List<Widget>();
if (movies != null) {
  var lengthOfList = movies.length;
  for (int i = 0; i < lengthOfList; i++) {
    Searchmodel movie = movies[i];
    // Image URL
    var imageURL = "https://image.tmdb.org/t/p/w500/" + movie.posterPath;
    // List item created with an image of the poster
    var listItem = new Padding(
      padding: const EdgeInsets.all(8.0),
      child: new Container(
        width: 105.0,
        height: 155.0,
        child: new Column(
          children: <Widget>[
            new GestureDetector(
              onTap: () {
                Navigator.push(
                  context,
                  new MaterialPageRoute(
                      builder: (_) => new Detail(movie.id)),
                );
              },
              child: new Container(
                width: 105.0,
                height: 155.0,
                child: new ClipRRect(
                  borderRadius: new BorderRadius.circular(7.0),
                  child: new Hero(
                    tag: movie.title,
                    child: new FadeInImage.memoryNetwork(
                      placeholder: kTransparentImage,
                      image: imageURL,
                      fit: BoxFit.cover,
                    ),
                  ),
                ),
                decoration: new BoxDecoration(boxShadow: [
                  new BoxShadow(
                      color: Colors.black12,
                      blurRadius: 10.0,
                      offset: new Offset(0.0, 10.0)),
                ]),
              ),
            ),
            new Padding(
              padding: const EdgeInsets.only(top: 18.0),
              child: new Text(
                movie.title,
                maxLines: 2,
              ),
            )
          ],
        ),
      ),
    );
    ;
    listElementWidgetList.add(listItem);
  }
} else {
  print("no movie search");
}
return listElementWidgetList;}

谢谢!

Answer 1

使用 path_provider :

1. 找到正确的本地路径:

    Future get _localPath async {      final directory = await getApplicationDocumentsDirectory();      return directory.path;    }

1. 创建对文件位置的引用

    Future get _localFile async {      final path = await _localPath;      return File('$path/yourfile.txt');    }

1. 向文件写入数据:

    Future writeCounter(int counter) async {      final file = await _localFile;      // Write the file      return file.writeAsString('blah bla blah');    }

1. 从文件中读取数据:

    Future readCounter() async {      try {        final file = await _localFile;        // Read the file        String contents = await file.readAsString();        return int.parse(contents);      } catch (e) {        // If we encounter an error, return 0        return 0;      }    }

如果你打印 contents = "blah blah blah"

文档:https://flutter.io/cookbook/persistence/reading-writing-files/

而且File有很多方法可以帮到你，结帐:

https://docs.flutter.io/flutter/dart-io/File-class.html