如何解决Flutter StaggeredGridView.countBuilder 滚动控件我遇到了这个错误“String”类型不是“index”的“int”类型的子类型
我在使用滚动控制器控制网格视图时遇到问题。我遇到了错误（“String”类型不是“index”的“int”类型的子类型）。但是在使用滚动控制器之前它是完美的。我不需要更改以消除此错误。我还在 stackoverflow 中检查了与此相关的其他问题，但无法解决。任何人都可以检查并告诉我可以在此处进行哪些更改以消除错误并显示数据，以及我的条件是否适合在每个滚动端加载 10 个数据。
import 'dart:convert';
import 'package:Flutter_staggered_grid_view/Flutter_staggered_grid_view.dart';
import 'package:gridview_screoll/grid_content.dart';
import 'package:http/http.dart' as http;
import 'package:Flutter/material.dart';
import 'constant.dart';
class ScrollableGrid extends StatefulWidget {
@override
_ScrollableGridState createState() => _ScrollableGridState();
}
class _ScrollableGridState extends State<ScrollableGrid> {
List data = [];
bool isLoading = false;
ScrollController _scrollController;
int pageCount = 1;
@override
void initState() {
// Todo: implement initState
super.initState();
this.fetchTopProducts();
addItemIntoLisT(pageCount);
_scrollController = new ScrollController(initialScrollOffset: 5.0)
..addListener(_scrollListener);
}
_scrollListener() {
if (_scrollController.offset >=
_scrollController.position.maxScrollExtent &&
!_scrollController.position.outOfRange) {
setState(() {
isLoading = true;
if (isLoading) {
pageCount = pageCount + 1;
addItemIntoLisT(pageCount);
}
});
}
}
void addItemIntoLisT(var pageCount) {
for (int i = (pageCount * 10) - 10; i < pageCount * 10; i++) {
fetchTopProducts();
isLoading = false;
}
}
@override
void dispose() {
_scrollController.dispose();
super.dispose();
}
fetchTopProducts() async {
setState(() {
isLoading = true;
});
var url = base_api + "api_frontend/top_products";
var response = await http.get(url);
print(response.body);
if (response.statusCode == 200) {
setState(() {
data.add(json.decode(response.body)['top_products']);
isLoading = false;
});
} else {
setState(() {
data = [];
isLoading = false;
});
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
elevation: 0.1,backgroundColor: Colors.indigo,title: Text('GridControll'),//backgroundColor: Color.fromrGBO(244,246,249,1),),body: SingleChildScrollView(
child: Column(
children: [
Container(
height: MediaQuery.of(context).size.height * 88/100,color: Color.fromrGBO(244,margin: const EdgeInsets.only(
left: 0.0,bottom: 2.0,right: 0.0,top: 0),child: getBody2(),],);
}
Widget getBody2() {
if (isLoading || data.length == 0) {
return Center(
child: CircularProgressIndicator(
valueColor: new AlwaysstoppedAnimation<Color>(primary)));
}
return StaggeredGridView.countBuilder(
padding: const EdgeInsets.all(10.0),controller: _scrollController,shrinkWrap: true,// physics: NeverScrollableScrollPhysics(),crossAxisCount: 2,itemCount: data.length - 1,itemBuilder: (context,index) {
return GestureDetector(
onTap: () {
Navigator.push(
context,MaterialPageRoute(
//builder: (context) => ProductDetails(item: data2[index]),builder: (context) => productDetail(data[index]),);
},child: cardItem2(data[index]));
},staggeredTileBuilder: (int index) => StaggeredTile.fit(1),mainAxisspacing: 10.0,crossAxisspacing: 10.0,);
}
}
这是 grid_content.dart：
import 'package:html_unescape/html_unescape.dart';
import 'package:Flutter/material.dart';
Widget cardItem2(item) {
// var img = item['thumbnail'];
// var thumbnail = base_api+"uploads/product_thumbnails/"+img;
var productId = item['product_id'];
var thumbnail = item['thumbnail'];
var unescape = new HtmlUnescape();
var name = unescape.convert(item['name']);
var unit = item['unit'];
var discount = item['discount'];
var price = item['price'];
var discountPrice = item['discount_price'];
return discount != '0%' ? Card(
elevation: 6,shadowColor: Colors.white,shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(9.0)),child: Stack(
fit: StackFit.loose,alignment: Alignment.center,children: [
Column(
children: <Widget>[
Stack(
children: [
ClipRRect(
borderRadius: BorderRadius.only(topRight: Radius.circular(9),topLeft: Radius.circular(9)),child: FadeInImage.assetNetwork(
placeholder: 'assets/loading_animated.gif',image: thumbnail,height: 110,width: double.infinity,fit: BoxFit.cover,Padding(
padding: const EdgeInsets.only(left:6.0,right: 6.0),child: Row(
children: [
Expanded(
child: Padding(
padding: const EdgeInsets.all(4.0),child: Column(
crossAxisAlignment: CrossAxisAlignment.start,children: [
Text(
name,style: TextStyle(
fontSize: 16.0,color: Colors.black87,fontWeight: FontWeight.w100,Text(
unit,style: TextStyle(
fontSize: 12.0,color: Colors.black45,Row(
children: [
Expanded(
flex: 2,child: Text(
discountPrice,style: TextStyle(
fontSize: 16.0,color: Colors.green,fontWeight: FontWeight.w500,Expanded(
flex: 2,child: Text(
price,style: TextStyle(
fontSize: 12.0,color: Colors.black38,decoration: Textdecoration.lineThrough,ButtonTheme(
padding: EdgeInsets.symmetric(vertical: 4.0,horizontal: 6.0),//adds padding inside the button
materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,//limits the touch area to the button area
minWidth: 0,//wraps child's width
height: 25,child: FlatButton(
minWidth: 5,height: 40,color: Color.fromrGBO(100,186,2,onpressed: () {
},child: Icon(Icons.shopping_cart,color: Colors.white,shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10.0),side: BorderSide(color: Color.fromrGBO(100,)),) : Card(
elevation: 6,Row(
children: [
Expanded(
flex: 1,style: TextStyle(
fontSize: 15.0,materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,minWidth: 0,child: FlatButton(
minWidth: 10,//height: 40,);
}
productDetail(item) {
// var img = item['thumbnail'];
// var thumbnail = base_api+"uploads/product_thumbnails/"+img;
var productId = item['product_id'];
var thumbnail = item['thumbnail'];
var unescape = new HtmlUnescape();
var name = unescape.convert(item['name']);
var discount = item['discount'];
var price = item['price'];
var disPrice= item['discount_price'];
var unit = item['unit'];
return Scaffold(
appBar: AppBar(
elevation: 0.1,iconTheme: IconThemeData(color: Colors.white),backgroundColor: Colors.red,title: Center(
child: Padding(
padding: const EdgeInsets.only(right: 50),child: Text(
'Product Details',style: TextStyle(color: Colors.white),actions: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 15,right: 25.0),child: GestureDetector(
child: Stack(
alignment: Alignment.topCenter,children: <Widget>[
Icon(
Icons.favorite,onTap: () {},)
],body: SingleChildScrollView(
child: Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,crossAxisAlignment: CrossAxisAlignment.start,children: [
Padding(
padding: const EdgeInsets.all(8.0),child: Container(
child: FadeInImage.assetNetwork(
placeholder: 'assets/black_circle.gif',height: 210,width: 360,Center(
child: Card(
color: Colors.white38,child: Padding(
padding: const EdgeInsets.only(left: 12.0,right: 12,top: 4,bottom: 4),child: Text(
unit,style: TextStyle(
fontSize: 11,Padding(
padding: const EdgeInsets.only(top: 8.0),child: Center(
child: discount != '0%' ? Row(
mainAxisAlignment: MainAxisAlignment.center,children: [
Text(
disPrice,style: TextStyle(
fontSize: 22,fontWeight: FontWeight.bold),Padding(
padding: const EdgeInsets.only(left: 8.0),child: Text(
price,style: TextStyle(
fontSize: 18,color: Colors.black54,): Text(
price,style: TextStyle(
fontSize: 22,Padding(
padding: const EdgeInsets.only(top: 4.0),child: Center(
child: Text(
name,style: TextStyle(
fontSize: 18,Padding(
padding: const EdgeInsets.all(8.0),child: Divider(),Container(
child: Center(
child: Text(
'Quantity',style: TextStyle(color: Colors.black45,fontSize: 15),Container(
child: Center(
child: Text(
'1',style: TextStyle(
color: Colors.black,fontSize: 22,//child: Text(store.activeProduct.qty.toString()),Padding(
padding: const EdgeInsets.only(
left: 100.0,right: 100.0,bottom: 10.0),child: FlatButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(4)),side: BorderSide(color: Color.fromrGBO(41,193,126,1)),color: Color.fromrGBO(41,padding: EdgeInsets.only(top: 8,bottom: 8),child: Center(
child: Text(
'BUY Now',style: TextStyle(color: Colors.white,fontSize: 16),onpressed: () {
}),child: FlatButton(
padding: EdgeInsets.only(top: 8,child: Center(
child: Text(
'ADD TO CART',style: TextStyle(color: Color.fromrGBO(41,onpressed: () {
}),);
}
这里是json文件：
{
"top_products": [
{
"product_id": "63","category_id": "59","name": "Ice Cream","price": "$9","discount_price": "$8.91","discount": "1%","unit": "3 kg","thumbnail": "http://192.168.0.105/uploads/product_thumbnails/72908baa78a2db38f678283a2e483903.jpg"
},{
"product_id": "65","category_id": "47","name": "Malta","price": "$5","discount_price": "$4.5","discount": "10%","unit": "1 kg","thumbnail": "http://192.168.0.105/uploads/product_thumbnails/a63dcb5e4f883eb946585d287d25c397.jpg"
},{},...
],"message": "Top hundred products","status": 200,"validity": true
}
======== Exception caught by widgets library =======================================================
The following _TypeError was thrown building:
type 'String' is not a subtype of type 'int' of 'index'
When the exception was thrown,this was the stack:
#0 cardItem2 (package:gridview_screoll/grid_content.dart:7:23)
#1 _ScrollableGridState.getBody2.<anonymous closure> (package:gridview_screoll/scroll_grid.dart:130:20)
#2 SliverChildBuilderDelegate.build (package:Flutter/src/widgets/sliver.dart:449:22)
#3 SliverVariableSizeBoxAdaptorElement._build.<anonymous closure> (package:Flutter_staggered_grid_view/src/widgets/sliver.dart:144:38)
#4 _HashMap.putIfAbsent (dart:collection-patch/collection_patch.dart:140:29)
...
====================================================================================================
解决方法
itemCount: data.length - 1,
改成这样：
itemCount: data.length;
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