大家好，當我在顫抖中創建搜索代表時遇到這個問題我嘗試從 Firebase 呼叫資料并將其添加到串列類中，但它向我顯示了這個錯誤
List<dynamic> is not a subtype fo type List<Itemshop> of function result
問題在這里
List<ItemShop> ItemShopList = [];
CollectionReference ItemShopRef =
FirebaseFirestore.instance.collection('ItemShop');
List filterItemShop = [];
int counter = 0;
Future getData() async {
var responsce = await ItemShopRef.get();
responsce.docs.forEach((element) {
ItemShop itemShop = ItemShop(element["ItemCatgore"], element["ItemImage"],
element["ItemKG"], element['ItemName'], element["ItemPrice"]);
if (counter == 0) {
ItemShopList.add(itemShop);
}
});
print(ItemShopList);
return ItemShopList;
}
ItemShop 類
class ItemShop {
final String ItemCatgore, ItemImage, ItemKG, ItemName;
int ItemPrice;
ItemShop(this.ItemCatgore, this.ItemImage, this.ItemKG, this.ItemName,
this.ItemPrice);
}
完整代碼：
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
class SearchPage extends StatefulWidget {
const SearchPage({Key? key}) : super(key: key);
@override
State<SearchPage> createState() => _SearchPageState();
}
class _SearchPageState extends State<SearchPage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Color.fromARGB(255, 184, 132, 132),
actions: [
IconButton(
onPressed: () {
showSearch(context: context, delegate: mySearch());
},
icon: Icon(Icons.search))
],
),
);
}
}
class mySearch extends SearchDelegate {
List<ItemShop> ItemShopList = [];
CollectionReference ItemShopRef =
FirebaseFirestore.instance.collection('ItemShop');
List filterItemShop = [];
int counter = 0;
Future getData() async {
var responsce = await ItemShopRef.get();
responsce.docs.forEach((element) {
ItemShop itemShop = ItemShop(element["ItemCatgore"], element["ItemImage"],
element["ItemKG"], element['ItemName'], element["ItemPrice"]);
if (counter == 0) {
ItemShopList.add(itemShop);
}
});
print(ItemShopList);
return ItemShopList;
}
////////////////////////////////////////////////
@override
List<Widget>? buildActions(BuildContext context) {
return [
IconButton(
onPressed: () {
query = "";
},
icon: Icon(Icons.close))
];
}
@override
Widget? buildLeading(BuildContext context) {
return IconButton(
onPressed: () {
close(context, null);
},
icon: Icon(Icons.arrow_back));
}
@override
Widget buildResults(BuildContext context) {
return FutureBuilder(
future: getData(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data == null) {
return Center(
child: CircularProgressIndicator(),
);
} else {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, int i) {
return snapshot.data[i].ItemName == query
? Card(
child: Column(
children: [
Container(
color: Colors.grey[200],
height: 150,
width: double.infinity,
child: Text(
snapshot.data[i].ItemName,
textAlign: TextAlign.center,
style: TextStyle(fontSize: 35),
),
),
Container(
child: Text(snapshot.data[i].ItemName),
)
],
),
)
: Container();
});
}
});
}
@override
Widget buildSuggestions(BuildContext context) {
filterItemShop = ItemShopList.where((element) =>
element.ItemName.toLowerCase().contains(query.toLowerCase())).toList();
return FutureBuilder(
future: getData(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.data == null) {
return Center(
child: CircularProgressIndicator(),
);
} else {
return ListView.builder(
itemCount:
query == "" ? snapshot.data.length : filterItemShop.length,
itemBuilder: (BuildContext context, int i) {
return InkWell(
onTap: () {
query = query == ""
? ItemShopList[i].ItemName
: filterItemShop[i].ItemName;
showResults(context);
},
child: Card(
child: query == ""
? ListTile(
leading: Text(snapshot.data[i].ItemName),
title: Text(snapshot.data[i].ItemName),
subtitle: Text(snapshot.data[i].ItemName),
)
: ListTile(
leading: Text(filterItemShop[i].ItemName),
title: Text(filterItemShop[i].ItemName),
subtitle: Text(filterItemShop[i].ItemName),
),
),
);
});
}
});
}
}
class ItemShop {
final String ItemCatgore, ItemImage, ItemKG, ItemName;
int ItemPrice;
ItemShop(this.ItemCatgore, this.ItemImage, this.ItemKG, this.ItemName,
this.ItemPrice);
}
uj5u.com熱心網友回復：
在那里，我認為更好的方法不是針對每個人，而是針對地圖。并使用型別定義變數，因此只要不使用強制轉換方法就不會出現型別錯誤。final List<Itemshop> x = responsce.docs.map((e)=>Itemshop.fromMap(e.data()..docId = e.id)).toList(); return x;
ypu 也可以像return responsce.docs.map((e)=> ....
Itemshop 應該是 ItemShop，標準 dart 格式。
Itemshop.fromMap 是您在 Itemshop calss 中構建的函式。資料類總是有這種幫手。從地圖，到地圖，從Json，到Json。如果您不想自己撰寫，則在 dart for thius 中生成大量代碼。
uj5u.com熱心網友回復：
在futurebuilder中指定future的型別，這里是list itemshop，如下圖。
return FutureBuilder<List<ItemShop>>(
//TODO: YOUR CODE
);
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