Question

试图回到AppBar上的后退按钮以返回Main.dart，但出现错误。有什么线索让我错过了吗？

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:material_design_icons_flutter/material_design_icons_flutter.dart';

class ProductPage extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Stuff',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

var bannerItems = ["Building Material", "Vehicles", "Clothes", "Food and Drink","Outdoor Items"];
var bannerImage = [
  "images/buildingmaterial.png",
  "images/car.jpg",
  "images/clothing.jpg",
  "images/food.jpg",
  "images/outdooritems.jpg"
];

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var screenHeight = MediaQuery.of(context).size.height;
    var screenWidth = MediaQuery.of(context).size.width;

    Future<List<Widget>> createList() async {
      List<Widget> items = new List<Widget>();
      String dataString =
          await DefaultAssetBundle.of(context).loadString("assets/data.json");
      List<dynamic> dataJSON = jsonDecode(dataString);


      dataJSON.forEach((object) {

        String finalString= "";
        List<dynamic> dataList = object["placeItems"];
        dataList.forEach((item){
          finalString = finalString + item + " | ";
        });

        items.add(Padding(padding: EdgeInsets.all(2.0),
        child: Container(
          decoration: BoxDecoration(
              color: Colors.white,
            borderRadius: BorderRadius.all(Radius.circular(10.0)),
            boxShadow: [
              BoxShadow(
                color: Colors.black12,
                spreadRadius: 2.0,
                blurRadius: 5.0
              ),
            ]
          ),
          margin: EdgeInsets.all(5.0),
          child: Row(
            mainAxisSize: MainAxisSize.max,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: <Widget>[
              ClipRRect(
                borderRadius: BorderRadius.only(topLeft: Radius.circular(10.0),bottomLeft: Radius.circular(10.0)),
                child: Image.asset(object["placeImage"],width: 80,height: 80,fit: BoxFit.cover,),
              ),
              SizedBox(
                width: 250,
                child: Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: <Widget>[
                      Text(object["placeName"]),
                      Padding(
                        padding: const EdgeInsets.only(top: 2.0,bottom: 2.0),
                        child: Text(finalString,overflow: TextOverflow.ellipsis,style: TextStyle(fontSize: 12.0,color: Colors.black54,),maxLines: 1,),
                      ),
                      Text("Min. Order: ${object["minOrder"]}",style: TextStyle(fontSize: 12.0,color: Colors.black54),)
                    ],
                  ),
                ),
              )
            ],
          ),
        ),));
      });

      return items;
    }

    return Scaffold(
      appBar: AppBar(
      leading: IconButton(
      icon: Icon(Icons.arrow_back, color: Colors.black),
      onPressed: () => Navigator.push(
        context,
        MaterialPageRoute(
          builder: (_) => Main(),
           )),
  ),
        title: Text('Product Page'),
        backgroundColor: Colors.deepOrange,
      ),
      body: Container(
        height: screenHeight,
        width: screenWidth,
        child: SafeArea(
            child: SingleChildScrollView(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              Padding(
                padding: const EdgeInsets.fromLTRB(10, 5, 10, 5),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: <Widget>[
                   // IconButton(icon: Icon(Icons.arrow_back), onPressed: () {}),
                    //Text("Categories",
                   //   style: TextStyle(fontSize: 50, fontFamily: "Samantha"),),
                   // IconButton(icon: Icon(Icons.person), onPressed: () {})
                  ],
                ),
              ),
              BannerWidgetArea(),
              Container(
                child: FutureBuilder(
                    initialData: <Widget>[Text("")],
                    future: createList(),
                    builder: (context,snapshot){
                      if(snapshot.hasData){
                        return Padding(
                          padding: EdgeInsets.all(8.0),
                          child: ListView(
                            primary: false,
                            shrinkWrap: true,
                            children: snapshot.data,
                          ),
                        );
                      } else {
                        return CircularProgressIndicator();
                      }
                    }),
              )
            ],
          ),
        )),
      ),
      floatingActionButton: FloatingActionButton(onPressed: (){},
          backgroundColor: Colors.black,
      child: Icon(MdiIcons.food,color: Colors.white,)),
    );
  }
}



class BannerWidgetArea extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var screenWidth = MediaQuery.of(context).size.width;

    PageController controller =
        PageController(viewportFraction: 0.8, initialPage: 1);

    List<Widget> banners = new List<Widget>();

    for (int x = 0; x < bannerItems.length; x++) {
      var bannerView = Padding(
        padding: EdgeInsets.all(10.0),
        child: Container(
          child: Stack(
            fit: StackFit.expand,
            children: <Widget>[
              Container(
                decoration: BoxDecoration(
                    borderRadius: BorderRadius.all(Radius.circular(20.0)),
                    boxShadow: [
                      BoxShadow(
                          color: Colors.black38,
                          offset: Offset(2.0, 2.0),
                          blurRadius: 5.0,
                          spreadRadius: 1.0)
                    ]),
              ),
              ClipRRect(
                borderRadius: BorderRadius.all(Radius.circular(20.0)),
                child: Image.asset(
                  bannerImage[x],
                  fit: BoxFit.cover,
                ),
              ),
              Container(
                decoration: BoxDecoration(
                    borderRadius: BorderRadius.all(Radius.circular(20.0)),
                    gradient: LinearGradient(
                        begin: Alignment.topCenter,
                        end: Alignment.bottomCenter,
                        colors: [Colors.transparent, Colors.black])),
              ),
              Padding(
                padding: EdgeInsets.all(10.0),
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.end,
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(
                      bannerItems[x],
                      style: TextStyle(fontSize: 25.0, color: Colors.white),
                    ),

                  ],
                ),
              )
            ],
          ),
        ),
      );
      banners.add(bannerView);
    }

    return Container(
      width: screenWidth,
      height: screenWidth * 9 / 16,
      child: PageView(
        controller: controller,
        scrollDirection: Axis.horizontal,
        children: banners,
      ),
    );
  }
}

Main.dart

import 'package:flutter/material.dart';
import 'package:mics_delta/privacypage.dart';
import 'package:mics_delta/productpage.dart';
import 'package:mics_delta/searchpage.dart';
import 'package:mics_delta/aboutus.dart';


void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Stuff',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomeScreen(),
    );
  }
}

class HomeScreen extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Stuff'),
        backgroundColor: Colors.blue,
      ),
      drawer: Drawer(
        child: ListView(
          children: <Widget>[
            DrawerHeader(
              decoration: BoxDecoration(
                gradient: LinearGradient(colors: <Color>[
                  Colors.red[300],
                  Colors.red[100],
                ])
              ),
              child: Container(
                child: Column(
                  children: <Widget>[
                    Material(
                      borderRadius: BorderRadius.all(Radius.circular(40.0)),
                      child: Image.asset('images/Canada_flag.png', width: 100,height: 100,),
                      ),
                      Text('Thats one good looking Flag', style: TextStyle(color: Colors.white, fontSize: 16.0),)
                  ],
                ),
                )),
            Column(
              children: <Widget>[
                CustomListTile(Icons.search,'Search', () {
                  Navigator.push(context, MaterialPageRoute(builder: (context) => SearchPage())); 
                  }),
              ],
            ),

            Column(
              children: <Widget>[
                CustomListTile(Icons.fastfood,'Products', () {
                  Navigator.push(context, MaterialPageRoute(builder: (context) => ProductPage())); 
                  }),
              ],
            ),
            CustomListTile(Icons.add,'Add Products',()=>{}),
            Column(
              children: <Widget>[
                CustomListTile(Icons.people,'About Us', () {
                  Navigator.push(context, MaterialPageRoute(builder: (context) => AboutUsPage())); 
                  }),
              ],
            ),
            Column(
              children: <Widget>[
                CustomListTile(Icons.vpn_lock,'Privacy', () {
                  Navigator.push(context, MaterialPageRoute(builder: (context) => PrivacyPage())); 
                  }),
              ],
            ),
          ],
        ),)
    );
  }
}

class CustomListTile extends StatelessWidget{

  IconData icon;
  String text;
  Function onTap;

  CustomListTile(this.icon, this.text, this.onTap,);

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(8.0, 0, 8.0, 0),
      child: Container(
        decoration: BoxDecoration(
          border: Border(bottom: BorderSide(color: Colors.grey.shade400))
        ),
        child: InkWell(
          splashColor: Colors.orangeAccent,
          onTap: onTap,
          child: Container(
            height: 50,
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: <Widget>[
                Row(
                  children: <Widget>[
                    Icon(icon),
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(text, style: TextStyle(
                        fontSize: 16.0
                      ),
                      ),
                    ),
                  ],
                ),

                Icon(Icons.arrow_right)
              ],
            ),
          ),
        ),
      ),
    );
  }
}

Answer 1

与其将小部件再次放置在堆栈顶部，不如将其从堆栈中弹出。检查下面的代码，它运行完美，

  class ProductPage extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Stuff',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              Text(
                'This is the product page',
                style: TextStyle(
                  fontSize: 25,
                  fontWeight: FontWeight.w500,
                ),
              ),
              SizedBox(
                width: 150,
                height: 45,
                child: FlatButton(
                  color: Colors.blue,
                  onPressed: () => Navigator.push(
                    context,
                    MaterialPageRoute(
                      builder: (_) => MyHomePage(),
                    ),
                  ),
                  child: Center(
                    child: Text('Go to home page'),
                  ),
                ),
              )
            ],
          ),
        ),
      ),
    );
  }
}

输出：

希望这会有所帮助。

更新：尝试一下。

 IconButton(
          icon: Icon(Icons.arrow_back, color: Colors.black),
          onPressed: () => Navigator.pushReplacement(
            context,
            MaterialPageRoute(
              builder: (context) => HomeScreen(),
            ),
          ),
        ),

没有为类“ MyHomePage”定义“ Main”方法

1 个答案: