如何在flutter中调用之前已有的main.dart中的changeNotifier？
How to call changeNotifier in the main.dart that already have one before in flutter?
我使用提供程序在一页中显示来自 firestore 的数据，然后我将数据传递到第二页，然后我在 main.dart 中调用了 changenotifier 。
但是每当我尝试导航到第二页时，它都会显示此错误：
"I/flutter ( 1763): Another exception was thrown: setState() or markNeedsBuild() called during build."
我不知道该怎么办。
- 注意：在
main.dart之前我已经有一个changenotifier了。
首页代码：
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shopping/pages/product_details.dart';
import 'package:shopping/provider/app_provider.dart';
import 'package:shopping/models/product.dart';
class Products extends StatefulWidget {
@override
ProductsState createState() => ProductsState();
}
class ProductsState extends State<Products> {
List<Product> products;
String img;
@override
Widget build(BuildContext context) {
final productProvider = Provider.of<CRUDModel>(context);
// productProvider.changeProductPage(PAGESTATUS.PRODUCTS);
return StreamBuilder<QuerySnapshot>(
stream: productProvider.fetchProductsAsStream(),
builder: (context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasData) {
products = snapshot.data.documents
.map((doc) => Product.fromMap(doc.data, doc.documentID))
.toList();
return GridView.builder(
itemCount: products.length,
gridDelegate:new SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount:2),
itemBuilder: (BuildContext context, index){
return Padding(
padding:const EdgeInsets.all(4.0),
child:SingleProd(
product:products[index]
// prodPicture: productList[index]['picture'],
//prodOldPrice: productList[index]['oldPrice'],
//prodPrice: productList[index]['price'],
),
);
}
);
}
else {
return Text('fetching');
}
}
);
}
}
class SingleProd extends StatelessWidget {
//final prodName;
//final prodPicture;
//final prodOldPrice;
//final prodPrice;
final Product product;
SingleProd({ @required this.product});
//SingleProd({product.picture});
@override
Widget build(BuildContext context) {
//final appProvider=Provider.of<CRUDModel>(context);
return Card(
child: Hero(tag: product.id,
child:
Material( child: InkWell(
onTap: (){
// if(appProvider.selectedPage==PAGESTATUS.PRODUCTDETAILS){
// appProvider.changeProductPage(PAGESTATUS.PRODUCTDETAILS);
Navigator.of(context).push(new MaterialPageRoute(builder: (context)=>ProductDetails(
//here we are passing the value of the products to Product detail page
productDetailName:product.name,
productDetailNewPrice:product.price,
productDetailPicture:product.picture,
//productDetailOldPrice:prodOldPrice,
//productDetailNewPrice:prodPrice,
//productDetailPicture: prodPicture,
)
)
);
//}
},
child:GridTile(
footer: Container(
color: Colors.white,
child: new Row(
children: <Widget>[
new Expanded(
child: new Text(product.name, style: TextStyle(fontWeight: FontWeight.bold, fontSize:16.0),),
),
new Text(
'$${product.price} ', style: TextStyle(color: Colors.red, fontWeight: FontWeight.bold),)
],
)
),
child:Image.network('${product.picture}.jpg', //Image.asset('assets/${product.picture}.jpg',
fit: BoxFit.cover,),
),
),
),
),
);
}
}
Future<Widget>_displayImages(){
}
第二页代码：
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shopping/provider/app_provider.dart';
//import 'package:shopping/main.dart';
import './home.dart';
class ProductDetails extends StatefulWidget {
final productDetailName;
final productDetailNewPrice;
final productDetailOldPrice;
final productDetailPicture;
ProductDetails(
{
this.productDetailName,
this.productDetailNewPrice,
this.productDetailOldPrice,
this.productDetailPicture,
}
);
@override
_ProductDetailsState createState() => _ProductDetailsState();
}
class _ProductDetailsState extends State<ProductDetails> {
@override
Widget build(BuildContext context) {
ChangeNotifierProvider<CRUDModel>(create: (context) => CRUDModel());
return Scaffold(
appBar: new AppBar(
elevation: 0.1 ,
backgroundColor: Colors.red,
title: InkWell(
onTap: (){Navigator.push(context, MaterialPageRoute(builder:(context)=>new HomePage()));},
child: Text("MyShop")),
actions: <Widget>[
new IconButton(icon: Icon(Icons.search, color: Colors.white,), onPressed:(){},),
],
),
body: new ListView(
children: <Widget>[
new Container(
height: 300.0,
child: GridTile(
child: Container(
color: Colors.white,
child: Image.network(widget.productDetailPicture),
),
footer: Container(
color: Colors.white70,
child: ListTile(
leading: Text(widget.productDetailName, style: TextStyle(
fontWeight: FontWeight.bold, fontSize: 15.00,
),
),
title: new Row(
children: <Widget>[
Expanded(
child: new Text("$${widget.productDetailOldPrice}",style: TextStyle(
color: Colors.grey, decoration: TextDecoration.lineThrough,
),
)
),
Expanded(
child: new Text("$${widget.productDetailNewPrice}",style: TextStyle(
fontWeight: FontWeight.bold, color: Colors.red
),
)
)
],
),
),
),
),
),
//The First button
Row(
children: <Widget>[
//The Size Button
Expanded(
child: MaterialButton(
onPressed: (){
showDialog(context:context,
builder:(context){
return new AlertDialog(
title: new Text("Size"),
content: new Text("Choose the Size"),
actions: <Widget>[
new MaterialButton(onPressed: (){
Navigator.of(context).pop();
},
child: new Text("Close"),
),
],
);
}
);
},
color: Colors.white,
textColor: Colors.grey,
elevation: 0.2,
child: Row(
children: <Widget>[
Expanded(
child: new Text("Size")
),
Expanded(
child:new Icon(Icons.arrow_drop_down),
),
],
),
),
),
Expanded(
child: MaterialButton(
onPressed: (){
showDialog(context:context,
builder:(context){
return new AlertDialog(
title: new Text("Colors"),
content: new Text("Choose a Color"),
actions: <Widget>[
new MaterialButton(onPressed: (){
Navigator.of(context).pop();
},
child: new Text("Close"),
),
],
);
}
);
},
color: Colors.white,
textColor: Colors.grey,
elevation: 0.2,
child: Row(
children: <Widget>[
Expanded(
child: new Text("Color")
),
Expanded(
child:new Icon(Icons.arrow_drop_down),
),
],
),
),
),
Expanded(
child: MaterialButton(
onPressed: (){
showDialog(context:context,
builder:(context){
return new AlertDialog(
title: new Text("Quantity"),
content: new Text("Choose the Quantity"),
actions: <Widget>[
new MaterialButton(onPressed: (){
Navigator.of(context).pop();
},
child: new Text("Close"),
),
],
);
}
);
},
color: Colors.white,
textColor: Colors.grey,
elevation: 0.2,
child: Row(
children: <Widget>[
Expanded(
child: new Text("QTY")
),
Expanded(
child:new Icon(Icons.arrow_drop_down),
),
],
),
),
),
],
),
//The Second button
Row(
children: <Widget>[
//The Size Button
Expanded(
child: MaterialButton(
onPressed: (){},
color: Colors.red,
textColor: Colors.white,
elevation: 0.2,
child: new Text("Buy Now"),
),
),
new IconButton(icon: Icon(Icons.add_shopping_cart, color: Colors.red,), onPressed: null,),
new IconButton(icon: Icon(Icons.favorite_border, color: Colors. red,), onPressed: null,),
],
),
new Divider(),
new ListTile(
title: Text("Product Description", style: TextStyle(fontWeight: FontWeight.bold),),
subtitle: new Text("Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets",),
),
new Divider(),
new Row(
children: <Widget>[
new Padding(padding: const EdgeInsets.fromLTRB(12.0, 5.0, 5.0, 5.0),
child: new Text("Product Name", style: TextStyle(color: Colors.grey),),),
new Padding(padding: EdgeInsets.all(5.0),
child: new Text(widget.productDetailName),)
],
),
new Row(
children: <Widget>[
//remember to create product brand
new Padding(padding: const EdgeInsets.fromLTRB(12.0, 5.0, 5.0, 5.0),
child: new Text("Product Brand", style: TextStyle(color: Colors.grey),),),
new Padding(padding: EdgeInsets.all(5.0),
child: new Text("Brand X"),),
],
),
new Row(
children: <Widget>[
//Add the product condition
new Padding(padding: const EdgeInsets.fromLTRB(12.0, 5.0, 5.0, 5.0),
child: new Text("Product Condition", style: TextStyle(color: Colors.grey),),),
new Padding(padding: EdgeInsets.all(5.0),
child: new Text("New"),)
],
),
new Divider(),
Padding(padding: const EdgeInsets.all(8.0),
child: new Text("Similar Products"),),
//Similar Products
new Container(
height: 360.0,
child: SimilarProducts(),
)
],
),
);
}
}
class SimilarProducts extends StatefulWidget {
@override
_SimilarProductsState createState() => _SimilarProductsState();
}
class _SimilarProductsState extends State<SimilarProducts> {
var productList=[
{
"name":"Black Dress",
"picture":"images/products/dress2.jpeg",
"oldPrice":150,
"price": 80,
},
{
"name":" M Pant1",
"picture":"images/products/pants1.jpg",
"oldPrice":120,
"price": 50,
},
{
"name":"Hill",
"picture":"images/products/hills1.jpeg",
"oldPrice":130,
"price": 80,
},
{
"name":"W Skirt",
"picture":"images/products/skt1.jpeg",
"oldPrice":150,
"price": 100,
},
];
@override
Widget build(BuildContext context) {
return GridView.builder(
itemCount: productList.length,
gridDelegate:new SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount:2),
itemBuilder: (BuildContext context, int index){
return SimilarSingleProd(
prodName: productList[index]['name'],
prodPicture: productList[index]['picture'],
prodOldPrice: productList[index]['oldPrice'],
prodPrice: productList[index]['price'],
);
}
);
}
}
class SimilarSingleProd extends StatelessWidget {
final prodName;
final prodPicture;
final prodOldPrice;
final prodPrice;
SimilarSingleProd({this.prodName, this.prodPicture,this.prodOldPrice,this.prodPrice});
@override
Widget build(BuildContext context) {
return Card(
child: Hero(tag: new Text("hero 1"),
child:
Material( child: InkWell(
onTap: ()=>Navigator.of(context).push(new MaterialPageRoute(builder: (context)=>ProductDetails(
//here we are passing the value of the products to Product detail page
productDetailName:prodName,
productDetailOldPrice:prodOldPrice,
productDetailNewPrice:prodPrice,
productDetailPicture: prodPicture,
)
)
),
child:GridTile(
footer: Container(
color: Colors.white,
child: new Row(
children: <Widget>[
new Expanded(
child: new Text(prodName, style: TextStyle(fontWeight: FontWeight.bold, fontSize:16.0),),
),
new Text("$$prodPrice", style: TextStyle(color: Colors.red, fontWeight: FontWeight.bold),)
],
)
),
child: Image.asset(prodPicture,
fit: BoxFit.cover,),
),
),
),
),
);
}
}
main.dart代码：
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shopping/pages/home.dart';
import 'package:shopping/pages/splash.dart';
import 'package:shopping/provider/app_provider.dart';
import 'provider/user_provider.dart';
import './pages/login.dart';
//import 'package:path_provider/path_provider.dart';
/*void main() {
runApp(
new MaterialApp(
debugShowCheckedModeBanner: false,
theme: ThemeData(
primaryColor: Colors.blue.shade900
),
home: Login(),
)
);
}*/
void main() {
WidgetsFlutterBinding.ensureInitialized();
runApp(MultiProvider(providers: [
ChangeNotifierProvider.value(value: UserProvider.initialize()),
//second notifier that is given me problem
ChangeNotifierProvider.value(value: CRUDModel()),
],
child:new MaterialApp(
debugShowCheckedModeBanner: false,
theme: ThemeData(
primaryColor: Colors.blue.shade900
),
home:ScreenController(),
),
),
);
}
class ScreenController extends StatelessWidget {
@override
Widget build(BuildContext context) {
final user=Provider.of<UserProvider>(context);
switch(user.status){
case Status.Uninitialized:
return Splash();
case Status.UnAuthenticated:
case Status.Authenticating:
return Login();
case Status.Authenticated:
return HomePage();
default:
return Login();
}
}
}
提供商本身
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:shopping/db/Api.dart';
import 'package:shopping/models/product.dart';
enum PAGESTATUS { INITIAL, PRODUCTS, PRODUCTDETAILS, PRODUCTFETCHFAIL }
class CRUDModel extends ChangeNotifier {
PAGESTATUS _pageStatus = PAGESTATUS.INITIAL;
PAGESTATUS get pageStatus => _pageStatus;
//Api _api = locator<Api>();
String path = "Products";
Api _api = Api();
List<Product> products;
Future<List<Product>> fetchProducts() async {
try {
//notifyListeners();
var result = await _api.getDataCollection();
products = result.documents
.map((doc) => Product.fromMap(doc.data, doc.documentID))
.toList();
} catch (e) {
notifyListeners();
print(e.toString());
}
return products;
}
Stream<QuerySnapshot> fetchProductsAsStream() {
notifyListeners();
return _api.streamDataCollection();
}
}
您的 fetchProductsAsStream 方法在调用后立即调用 notifyListeners()，这可能是导致问题的原因。在创建 StreamBuilder 时从 build 函数调用此方法，但 notifyListeners 将触发额外的 build，因此会出现错误。您应该能够简单地从 fetchProductsAsStream 中删除 notifyListeners，因为无论如何都没有要通知的更改。
我使用提供程序在一页中显示来自 firestore 的数据，然后我将数据传递到第二页，然后我在 main.dart 中调用了 changenotifier 。
但是每当我尝试导航到第二页时，它都会显示此错误：
"I/flutter ( 1763): Another exception was thrown: setState() or markNeedsBuild() called during build."
我不知道该怎么办。
- 注意：在
main.dart之前我已经有一个changenotifier了。
首页代码：
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shopping/pages/product_details.dart';
import 'package:shopping/provider/app_provider.dart';
import 'package:shopping/models/product.dart';
class Products extends StatefulWidget {
@override
ProductsState createState() => ProductsState();
}
class ProductsState extends State<Products> {
List<Product> products;
String img;
@override
Widget build(BuildContext context) {
final productProvider = Provider.of<CRUDModel>(context);
// productProvider.changeProductPage(PAGESTATUS.PRODUCTS);
return StreamBuilder<QuerySnapshot>(
stream: productProvider.fetchProductsAsStream(),
builder: (context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasData) {
products = snapshot.data.documents
.map((doc) => Product.fromMap(doc.data, doc.documentID))
.toList();
return GridView.builder(
itemCount: products.length,
gridDelegate:new SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount:2),
itemBuilder: (BuildContext context, index){
return Padding(
padding:const EdgeInsets.all(4.0),
child:SingleProd(
product:products[index]
// prodPicture: productList[index]['picture'],
//prodOldPrice: productList[index]['oldPrice'],
//prodPrice: productList[index]['price'],
),
);
}
);
}
else {
return Text('fetching');
}
}
);
}
}
class SingleProd extends StatelessWidget {
//final prodName;
//final prodPicture;
//final prodOldPrice;
//final prodPrice;
final Product product;
SingleProd({ @required this.product});
//SingleProd({product.picture});
@override
Widget build(BuildContext context) {
//final appProvider=Provider.of<CRUDModel>(context);
return Card(
child: Hero(tag: product.id,
child:
Material( child: InkWell(
onTap: (){
// if(appProvider.selectedPage==PAGESTATUS.PRODUCTDETAILS){
// appProvider.changeProductPage(PAGESTATUS.PRODUCTDETAILS);
Navigator.of(context).push(new MaterialPageRoute(builder: (context)=>ProductDetails(
//here we are passing the value of the products to Product detail page
productDetailName:product.name,
productDetailNewPrice:product.price,
productDetailPicture:product.picture,
//productDetailOldPrice:prodOldPrice,
//productDetailNewPrice:prodPrice,
//productDetailPicture: prodPicture,
)
)
);
//}
},
child:GridTile(
footer: Container(
color: Colors.white,
child: new Row(
children: <Widget>[
new Expanded(
child: new Text(product.name, style: TextStyle(fontWeight: FontWeight.bold, fontSize:16.0),),
),
new Text(
'$${product.price} ', style: TextStyle(color: Colors.red, fontWeight: FontWeight.bold),)
],
)
),
child:Image.network('${product.picture}.jpg', //Image.asset('assets/${product.picture}.jpg',
fit: BoxFit.cover,),
),
),
),
),
);
}
}
Future<Widget>_displayImages(){
}
第二页代码：
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shopping/provider/app_provider.dart';
//import 'package:shopping/main.dart';
import './home.dart';
class ProductDetails extends StatefulWidget {
final productDetailName;
final productDetailNewPrice;
final productDetailOldPrice;
final productDetailPicture;
ProductDetails(
{
this.productDetailName,
this.productDetailNewPrice,
this.productDetailOldPrice,
this.productDetailPicture,
}
);
@override
_ProductDetailsState createState() => _ProductDetailsState();
}
class _ProductDetailsState extends State<ProductDetails> {
@override
Widget build(BuildContext context) {
ChangeNotifierProvider<CRUDModel>(create: (context) => CRUDModel());
return Scaffold(
appBar: new AppBar(
elevation: 0.1 ,
backgroundColor: Colors.red,
title: InkWell(
onTap: (){Navigator.push(context, MaterialPageRoute(builder:(context)=>new HomePage()));},
child: Text("MyShop")),
actions: <Widget>[
new IconButton(icon: Icon(Icons.search, color: Colors.white,), onPressed:(){},),
],
),
body: new ListView(
children: <Widget>[
new Container(
height: 300.0,
child: GridTile(
child: Container(
color: Colors.white,
child: Image.network(widget.productDetailPicture),
),
footer: Container(
color: Colors.white70,
child: ListTile(
leading: Text(widget.productDetailName, style: TextStyle(
fontWeight: FontWeight.bold, fontSize: 15.00,
),
),
title: new Row(
children: <Widget>[
Expanded(
child: new Text("$${widget.productDetailOldPrice}",style: TextStyle(
color: Colors.grey, decoration: TextDecoration.lineThrough,
),
)
),
Expanded(
child: new Text("$${widget.productDetailNewPrice}",style: TextStyle(
fontWeight: FontWeight.bold, color: Colors.red
),
)
)
],
),
),
),
),
),
//The First button
Row(
children: <Widget>[
//The Size Button
Expanded(
child: MaterialButton(
onPressed: (){
showDialog(context:context,
builder:(context){
return new AlertDialog(
title: new Text("Size"),
content: new Text("Choose the Size"),
actions: <Widget>[
new MaterialButton(onPressed: (){
Navigator.of(context).pop();
},
child: new Text("Close"),
),
],
);
}
);
},
color: Colors.white,
textColor: Colors.grey,
elevation: 0.2,
child: Row(
children: <Widget>[
Expanded(
child: new Text("Size")
),
Expanded(
child:new Icon(Icons.arrow_drop_down),
),
],
),
),
),
Expanded(
child: MaterialButton(
onPressed: (){
showDialog(context:context,
builder:(context){
return new AlertDialog(
title: new Text("Colors"),
content: new Text("Choose a Color"),
actions: <Widget>[
new MaterialButton(onPressed: (){
Navigator.of(context).pop();
},
child: new Text("Close"),
),
],
);
}
);
},
color: Colors.white,
textColor: Colors.grey,
elevation: 0.2,
child: Row(
children: <Widget>[
Expanded(
child: new Text("Color")
),
Expanded(
child:new Icon(Icons.arrow_drop_down),
),
],
),
),
),
Expanded(
child: MaterialButton(
onPressed: (){
showDialog(context:context,
builder:(context){
return new AlertDialog(
title: new Text("Quantity"),
content: new Text("Choose the Quantity"),
actions: <Widget>[
new MaterialButton(onPressed: (){
Navigator.of(context).pop();
},
child: new Text("Close"),
),
],
);
}
);
},
color: Colors.white,
textColor: Colors.grey,
elevation: 0.2,
child: Row(
children: <Widget>[
Expanded(
child: new Text("QTY")
),
Expanded(
child:new Icon(Icons.arrow_drop_down),
),
],
),
),
),
],
),
//The Second button
Row(
children: <Widget>[
//The Size Button
Expanded(
child: MaterialButton(
onPressed: (){},
color: Colors.red,
textColor: Colors.white,
elevation: 0.2,
child: new Text("Buy Now"),
),
),
new IconButton(icon: Icon(Icons.add_shopping_cart, color: Colors.red,), onPressed: null,),
new IconButton(icon: Icon(Icons.favorite_border, color: Colors. red,), onPressed: null,),
],
),
new Divider(),
new ListTile(
title: Text("Product Description", style: TextStyle(fontWeight: FontWeight.bold),),
subtitle: new Text("Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets",),
),
new Divider(),
new Row(
children: <Widget>[
new Padding(padding: const EdgeInsets.fromLTRB(12.0, 5.0, 5.0, 5.0),
child: new Text("Product Name", style: TextStyle(color: Colors.grey),),),
new Padding(padding: EdgeInsets.all(5.0),
child: new Text(widget.productDetailName),)
],
),
new Row(
children: <Widget>[
//remember to create product brand
new Padding(padding: const EdgeInsets.fromLTRB(12.0, 5.0, 5.0, 5.0),
child: new Text("Product Brand", style: TextStyle(color: Colors.grey),),),
new Padding(padding: EdgeInsets.all(5.0),
child: new Text("Brand X"),),
],
),
new Row(
children: <Widget>[
//Add the product condition
new Padding(padding: const EdgeInsets.fromLTRB(12.0, 5.0, 5.0, 5.0),
child: new Text("Product Condition", style: TextStyle(color: Colors.grey),),),
new Padding(padding: EdgeInsets.all(5.0),
child: new Text("New"),)
],
),
new Divider(),
Padding(padding: const EdgeInsets.all(8.0),
child: new Text("Similar Products"),),
//Similar Products
new Container(
height: 360.0,
child: SimilarProducts(),
)
],
),
);
}
}
class SimilarProducts extends StatefulWidget {
@override
_SimilarProductsState createState() => _SimilarProductsState();
}
class _SimilarProductsState extends State<SimilarProducts> {
var productList=[
{
"name":"Black Dress",
"picture":"images/products/dress2.jpeg",
"oldPrice":150,
"price": 80,
},
{
"name":" M Pant1",
"picture":"images/products/pants1.jpg",
"oldPrice":120,
"price": 50,
},
{
"name":"Hill",
"picture":"images/products/hills1.jpeg",
"oldPrice":130,
"price": 80,
},
{
"name":"W Skirt",
"picture":"images/products/skt1.jpeg",
"oldPrice":150,
"price": 100,
},
];
@override
Widget build(BuildContext context) {
return GridView.builder(
itemCount: productList.length,
gridDelegate:new SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount:2),
itemBuilder: (BuildContext context, int index){
return SimilarSingleProd(
prodName: productList[index]['name'],
prodPicture: productList[index]['picture'],
prodOldPrice: productList[index]['oldPrice'],
prodPrice: productList[index]['price'],
);
}
);
}
}
class SimilarSingleProd extends StatelessWidget {
final prodName;
final prodPicture;
final prodOldPrice;
final prodPrice;
SimilarSingleProd({this.prodName, this.prodPicture,this.prodOldPrice,this.prodPrice});
@override
Widget build(BuildContext context) {
return Card(
child: Hero(tag: new Text("hero 1"),
child:
Material( child: InkWell(
onTap: ()=>Navigator.of(context).push(new MaterialPageRoute(builder: (context)=>ProductDetails(
//here we are passing the value of the products to Product detail page
productDetailName:prodName,
productDetailOldPrice:prodOldPrice,
productDetailNewPrice:prodPrice,
productDetailPicture: prodPicture,
)
)
),
child:GridTile(
footer: Container(
color: Colors.white,
child: new Row(
children: <Widget>[
new Expanded(
child: new Text(prodName, style: TextStyle(fontWeight: FontWeight.bold, fontSize:16.0),),
),
new Text("$$prodPrice", style: TextStyle(color: Colors.red, fontWeight: FontWeight.bold),)
],
)
),
child: Image.asset(prodPicture,
fit: BoxFit.cover,),
),
),
),
),
);
}
}
main.dart代码：
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shopping/pages/home.dart';
import 'package:shopping/pages/splash.dart';
import 'package:shopping/provider/app_provider.dart';
import 'provider/user_provider.dart';
import './pages/login.dart';
//import 'package:path_provider/path_provider.dart';
/*void main() {
runApp(
new MaterialApp(
debugShowCheckedModeBanner: false,
theme: ThemeData(
primaryColor: Colors.blue.shade900
),
home: Login(),
)
);
}*/
void main() {
WidgetsFlutterBinding.ensureInitialized();
runApp(MultiProvider(providers: [
ChangeNotifierProvider.value(value: UserProvider.initialize()),
//second notifier that is given me problem
ChangeNotifierProvider.value(value: CRUDModel()),
],
child:new MaterialApp(
debugShowCheckedModeBanner: false,
theme: ThemeData(
primaryColor: Colors.blue.shade900
),
home:ScreenController(),
),
),
);
}
class ScreenController extends StatelessWidget {
@override
Widget build(BuildContext context) {
final user=Provider.of<UserProvider>(context);
switch(user.status){
case Status.Uninitialized:
return Splash();
case Status.UnAuthenticated:
case Status.Authenticating:
return Login();
case Status.Authenticated:
return HomePage();
default:
return Login();
}
}
}
提供商本身
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:shopping/db/Api.dart';
import 'package:shopping/models/product.dart';
enum PAGESTATUS { INITIAL, PRODUCTS, PRODUCTDETAILS, PRODUCTFETCHFAIL }
class CRUDModel extends ChangeNotifier {
PAGESTATUS _pageStatus = PAGESTATUS.INITIAL;
PAGESTATUS get pageStatus => _pageStatus;
//Api _api = locator<Api>();
String path = "Products";
Api _api = Api();
List<Product> products;
Future<List<Product>> fetchProducts() async {
try {
//notifyListeners();
var result = await _api.getDataCollection();
products = result.documents
.map((doc) => Product.fromMap(doc.data, doc.documentID))
.toList();
} catch (e) {
notifyListeners();
print(e.toString());
}
return products;
}
Stream<QuerySnapshot> fetchProductsAsStream() {
notifyListeners();
return _api.streamDataCollection();
}
}
您的 fetchProductsAsStream 方法在调用后立即调用 notifyListeners()，这可能是导致问题的原因。在创建 StreamBuilder 时从 build 函数调用此方法，但 notifyListeners 将触发额外的 build，因此会出现错误。您应该能够简单地从 fetchProductsAsStream 中删除 notifyListeners，因为无论如何都没有要通知的更改。