firebase - flutter 错误 : type 'Future' is not a subtype of type 'List'

Question

我正在尝试构建一个包含不同游戏列表的应用。作为后端，我使用 Firebase 并且连接工作正常，我对其进行了测试。无论如何，我在用来自 firebase 的真实数据替换模拟数据时遇到了问题。我总是收到此错误:

type 'Future < dynamic>' is not a subtype of type 'List < Game>'

我有以下功能:

getGames() async{
 List newGamesList = [];

  QuerySnapshot result = awaitFirestore.instance.collection('products').getDocuments();
  List<DocumentSnapshot> documents = result.documents;
  documents.forEach((DocumentSnapshot doc) {
  Game game = new Game.fromDocument(doc);
  newGamesList.add(game);

});
}

“游戏”看起来像这样:

factory Game.fromDocument(DocumentSnapshot document) {

return new Game(
  name: document['name'],
  box: document['box'],
  cover: document['cover'],
  description: document['description'],

);
}

在我的构建小部件中，我调用“getGames”:

new HorizontalGameController(getGames()),

知道为什么会出现此错误以及如何解决吗？

编辑:

为了更好地理解这里是我的 Horizo​​ntalGameController:

class HorizontalGameController extends StatelessWidget {
HorizontalGameController(this.gameItems);
final List<Game> gameItems;

@override
Widget build(BuildContext context) {
return new SizedBox.fromSize(
  size: const Size.fromHeight(240.0),
  child: new ListView.builder(
      itemCount: 1,
      scrollDirection: Axis.horizontal,
      padding: const EdgeInsets.only(left: 12.0, top: 4.0),
      itemBuilder: (BuildContext context, int position) {
        return GameContainerItem(context, gameItems[position]);
      }),
);
}
}

Answer 1

getGames 不会返回您创建的游戏列表。使函数返回游戏列表。我无法测试，但请尝试一下

Future<List<Game>> getGames() async{
 List<Game> newGamesList = [];

  QuerySnapshot result = await Firestore.instance.collection('products').getDocuments();
  List<DocumentSnapshot> documents = result.documents;
  documents.forEach((DocumentSnapshot doc) {
  Game game = new Game.fromDocument(doc);
  newGamesList.add(game);

});

return newGamesList;
}

//then this
//new HorizontalGameController(await getGames()) //change this 

编辑 将 new Horizo​​ntalGameController(await getGames()) 更改为以下代码(用 futureBuilder 包装)。这将使小部件能够使用 future 的值(value)。

FutureBuilder<List<Game>>(
                            future: getGames(),
                            builder: (context, AsyncSnapshot<List<Game>> gamelistSnapshot){
                                  return (gamelistSnapshot.hasData)? HorizontalGameController(gamelistSnapshot.data) : Container();
                            },
                        )