如何在不刷新列表的情况下将多个小部件添加到列表

如何解决如何在不刷新列表的情况下将多个小部件添加到列表

所以从本质上讲，我正在尝试创建一个喜欢的购物车。我可以添加一个鞋子，也可以添加多个鞋子，但是一旦按下后退按钮并尝试添加另一个鞋子，我最终只会添加该鞋子，而以前尝试添加的其他鞋子不存在。

import 'package:flutter/material.dart';
import 'package:sample/model/products.dart';
import 'package:sample/pages/details_page.dart';
import 'package:sample/widgets/shoe_card.dart';

class Discover extends StatelessWidget {
  Discover();
  //padding: const EdgeInsets.all(8),@override
  Widget build(BuildContext context) {
    return Container(
      child: GridView.builder(
        padding: EdgeInsets.all(10),itemCount: products.length,gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
          crossAxisSpacing: 10,mainAxisSpacing: 10,crossAxisCount: 2,),itemBuilder: (context,index) => ShoeCard(
            product: products[index],press: () {
              Navigator.push(
                  context,MaterialPageRoute(
                      builder: (context) => Details(index)));
            }),);
  }
}

Details（）

import 'package:flutter/material.dart';
import 'package:sample/model/products.dart';
import 'package:sample/widgets/cart.dart';

class Details extends StatefulWidget {
  int newIndex;

  Details(this.newIndex);

  @override
  _DetailsState createState() => _DetailsState();
}

class _DetailsState extends State<Details> {
  List<Product> _list = new List<Product>();
  void _addList() {
    setState(() {
      print(widget.newIndex);
      var item = products[widget.newIndex];
      _list.add(item);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        actions: <Widget>[
          IconButton(
              onPressed: () {
                for (int i = 0; i < _list.length; i++) {
                  print(_list[widget.newIndex].name);
                }
                Navigator.push(context,MaterialPageRoute(builder: (context) => Cart(_list)));
              },icon: Icon(Icons.shopping_cart)),],elevation: 0,body: Container(
        margin: const EdgeInsets.fromLTRB(10,10,0),color: Colors.white,child: Padding(
          padding: const EdgeInsets.fromLTRB(2,2,child: Column(
            children: <Widget>[
              Column(
                mainAxisAlignment: MainAxisAlignment.start,children: <Widget>[
                  Divider(
                    color: Colors.black,indent: 50,endIndent: 40,Container(
                    child: Text(products[widget.newIndex].name),Divider(
                    color: Colors.black,Container(
                    height: 190,child: Image(
                      image: AssetImage(products[widget.newIndex].assetName),Container(
                    child: Text('Product Detail'),alignment: Alignment.topLeft,Container(
                    child: Divider(
                      endIndent: 240,Container(
                    height: 110,child: Text(
                      products[widget.newIndex].descript,style: TextStyle(fontSize: 10),textAlign: TextAlign.start,Container(
                    padding: const EdgeInsets.only(top: 58),alignment: Alignment.center,child: Stack(
                      children: <Widget>[
                        Container(
                          height: 50,decoration: BoxDecoration(
                              color: Colors.black,borderRadius: BorderRadius.only(
                                  topLeft: Radius.circular(24),topRight: Radius.circular(24))),Container(
                          alignment: Alignment.center,child: Row(
                            children: <Widget>[
                              Container(
                                child: IconButton(
                                  onPressed: () {
                                    print('tapped');
                                  },icon: Icon(Icons.favorite),Flexible(
                                fit: FlexFit.tight,child: Container(
                                  padding: EdgeInsets.only(left: 100),child: Text(
                                    products[widget.newIndex].price,style: TextStyle(
                                        color: Colors.white,letterSpacing: 2),Container(
                                padding: EdgeInsets.only(left: 70),child: IconButton(
                                  onPressed: _addList,icon: Icon(Icons.add_shopping_cart),)
                            ],)
                      ],);
  }
}

Cart
import 'package:flutter/material.dart';
import 'package:sample/model/products.dart';
import 'package:sample/widgets/shoe_card.dart';

// ignore: must_be_immutable
class Cart extends StatelessWidget {
  final List<Product> _cart;
  Cart(this._cart);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.white,body: Container(
          child: GridView.builder(
            padding: EdgeInsets.all(10),itemCount: _cart.length,gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisSpacing: 10,index) => ShoeCard(
              product: _cart[index],press: () {},));
  }
}

然后，当我尝试在购物车中添加多个鞋子时，在尝试添加第二个鞋子时出现此错误：

Exception caught by gesture ═══════════════════════════════════════════
The following RangeError was thrown while handling a gesture:
RangeError (index): Invalid value: Only valid value is 0: 1

When the exception was thrown,this was the stack
#0      List.[]  (dart:core-patch/growable_array.dart:146:60)
#1      _DetailsState.build.<anonymous closure> 
package:sample/pages/details_page.dart:32
#2      _InkResponseState._handleTap 
#3      _InkResponseState.build.<anonymous closure> 
package:flutter/…/material/ink_well.dart:862
#4      GestureRecognizer.invokeCallback 
package:flutter/…/gestures/recognizer.dart:182
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#a453e
    debugOwner: GestureDetector
    state: possible
    won arena
    finalPosition: Offset(332.3,51.7)
    finalLocalPosition: Offset(20.3,27.7)
    button: 1
    sent tap down