未定义命名参数“home” - Flutter

Question

我的 Flutter 项目遇到问题。 当我尝试在脚手架中调用 'home'-statement 时，它会抛出一个错误，指出The named parameter 'home' isn't defined 。 我已经尝试了很多，但我没有找到任何解决这个问题的方法。

另外，我最近开始研究 Flutter，这是我的第一个项目。 所以请指导我正确的方法，因为我正处于 Flutter 体验的学习阶段。 提前致谢。

文件结构：

 lib/
 ---components/
 ------appScaffold.dart
 ---pages/
 ------home.dart 
 main.dart

我已经实现了如下代码： -

main.dart

import 'package:flutter/material.dart';
import 'package:project/pages/home.dart';
import 'package:project/components/appScaffold.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return AppScaffold(
      home: HomePage(), //!Here's the problemt with 'home'
    );
  }
}

主页.dart

import 'package:project/main.dart';
import 'package:flutter/material.dart';
import 'package:bubble_bottom_bar/bubble_bottom_bar.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int currentPageIndex = 0;

  void changePage(int newPageIndex) {
    setState(() {
      currentPageIndex = newPageIndex;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Title'),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {},
        child: Icon(Icons.add),
        backgroundColor: Colors.red,
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.endDocked,
      bottomNavigationBar: BubbleBottomBar(
        opacity: .2,
        currentIndex: currentPageIndex,
        onTap: changePage,
        borderRadius: BorderRadius.vertical(top: Radius.circular(16)),
        elevation: 8,
        fabLocation: BubbleBottomBarFabLocation.end, //new
        hasNotch: true, //new
        hasInk: true, //new, gives a cute ink effect
        inkColor: Colors.black12, //optional, uses theme color if not specified
        items: <BubbleBottomBarItem>[
          BubbleBottomBarItem(
              //Home
              backgroundColor: Colors.red,
              icon: Icon(
                Icons.home,
                color: Colors.black,
              ),
              activeIcon: Icon(
                Icons.home,
                color: Colors.red,
              ),
              title: Text("text")),
          BubbleBottomBarItem(
              backgroundColor: Colors.deepPurple,
              icon: Icon(
                Icons.menu,
                color: Colors.black,
              ),
              activeIcon: Icon(
                Icons.menu,
                color: Colors.deepPurple,
              ),
              title: Text("text")),
          BubbleBottomBarItem(
              //Icon3
              backgroundColor: Colors.indigo,
              icon: Icon(
                Icons.menu,
                color: Colors.black,
              ),
              activeIcon: Icon(
                Icons.menu,
                color: Colors.indigo,
              ),
              title: Text("text")),
          BubbleBottomBarItem(
              //Icon 4
              backgroundColor: Colors.green,
              icon: Icon(
                Icons.menu,
                color: Colors.black,
              ),
              activeIcon: Icon(
                Icons.menu,
                color: Colors.green,
              ),
              title: Text("text"))
        ],
      ),
    );
  }
}

appScaffold.dart

import 'package:flutter/material.dart';
import 'package:project/main.dart';
import 'package:project/pages/home.dart';

class AppScaffold extends StatelessWidget {
  AppScaffold(this.home);
  final Widget home;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'MoneyTracker',
      theme: ThemeData(
        primarySwatch: Colors.indigo,
        primaryColor: Colors.indigo,
        secondaryHeaderColor: Colors.indigo,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: home,
    );
  }
}

Answer 1

问题是您的AppScaffold class 中的构造函数。 当你想命名一个参数时，你必须把它放在花括号中。 这看起来像：

import 'package:flutter/material.dart';
import 'package:project/main.dart';
import 'package:project/pages/home.dart';

class AppScaffold extends StatelessWidget {
  AppScaffold({this.home});
  final Widget home;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'MoneyTracker',
      theme: ThemeData(
        primarySwatch: Colors.indigo,
        primaryColor: Colors.indigo,
        secondaryHeaderColor: Colors.indigo,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: home,
    );
  }
}

当您想创建一个同时具有命名和位置 arguments 的构造函数时。 它看起来像：

MyClass(this.positional, {this.named, this.alsoNamed});

在这里您可以阅读更多关于 dart 中命名为 Arguments 的信息。