如何在 Flutter 的底部导航栏中设置默认选项卡？

Question

我目前有 5 个标签页，如何在启动应用程序时设置默认标签页？假设我希望帐户选项卡成为打开应用程序时的默认选项卡。

我该怎么做？顺便说一句，我使用 WebView 插件来显示网站的内容。

下面是我的 main.dart 文件的代码。我试过搜索，但我发现的所有解决方案都不适合我（我认为我搜索错误的单词。另外，我是新来的）非常感谢！

import 'package:syncshop/widgets/cart_page.dart';
import 'package:syncshop/widgets/categories_page.dart';
import 'package:syncshop/widgets/home_page.dart';
import 'package:syncshop/widgets/profile_account.dart';
import 'package:syncshop/widgets/search_page.dart';


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

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return MyAppState();
  }
}

class MyAppState extends State<MyApp> {
int _selectedPage = 0;
final _pageOptions = [
  HomeScreen(),
  CategoriesPage(),
  SearchPage(),
  CartPage(),
  ProfileAccount(),
];

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Sync Shop',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
      body: _pageOptions[_selectedPage],
      bottomNavigationBar: BottomNavigationBar(
          type: BottomNavigationBarType.fixed,
          currentIndex: _selectedPage,
          onTap: (int index) {
            setState((){
      _selectedPage = index;
            });
          },
          items: [
          BottomNavigationBarItem(icon: Icon(Icons.home), title: Text("Home"),
          ),
          BottomNavigationBarItem(icon: Icon(Icons.category), title: Text("Categories"),
          ),
          BottomNavigationBarItem(icon: Icon(Icons.search), title: Text("Search"),
          ),
          BottomNavigationBarItem(icon: Icon(Icons.shopping_cart), title: Text("Cart"),
          ),
          BottomNavigationBarItem(icon: Icon(Icons.account_circle), title: Text("Profile"),
          ),
          ],
          ),
      ),
      );
  }
}

Answer 1

您可以覆盖State 的initState 函数，并可以在那里放置一些初始代码。

所以对于你的例子，可以这样做。

...

class MyAppState extends State<MyApp> {
    int _selectedPage = 0;
    @override
    void initState() {
        super.initState();
        _selectedPage = 4;
    }

...

Answer 2

当你创建 BottomNavigationBar 时，将 this.currentindex 设置为你想要的索引

bottomNavigationBar: BottomNavigationBar(
          currentindex=1,//This line, it's default 0
          type: BottomNavigationBarType.fixed,
          currentIndex: _selectedPage,
          onTap: (int index) {
            setState(() {
              _selectedPage = index;
            });
          },

Answer 3

您必须使用标签控制器。

首先你需要在课堂上扩展TickerProviderStateMixin。

class MyAppState extends State<MyApp> with TickerProviderStateMixin {

}

然后定义 TabController 之类的，

_tabController = new TabController(length: _tabLength, vsync: this, initialIndex: 1);

最后在你的TabBarView中设置控制器

controller: _tabController,

Answer 4

这里初始化默认选项卡

int _selectedPage = 0;

您可以将其更改为您想要的任何选项卡，如果您想要个人资料

int _selectedPage = 4;

Answer 5

import 'package:flutter/material.dart';
import 'package:syncshop/widgets/cart_page.dart';
import 'package:syncshop/widgets/categories_page.dart';
import 'package:syncshop/widgets/home_page.dart';
import 'package:syncshop/widgets/profile_account.dart';
import 'package:syncshop/widgets/search_page.dart';

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

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return MyAppState();
  }
}

class MyAppState extends State<MyApp> {
  int _selectedPage = 4;

  final _pageOptions = [
    HomeScreen(),
    CategoriesPage(),
    SearchPage(),
    CartPage(),
    ProfileAccount(),
  ];

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Sync Shop',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: _pageOptions[_selectedPage],
        bottomNavigationBar: BottomNavigationBar(
          type: BottomNavigationBarType.fixed,
          currentIndex: _selectedPage,
          onTap: (int index) {
            setState(() {
              _selectedPage = index;
            });
          },
          items: [
            BottomNavigationBarItem(
              icon: Icon(Icons.home),
              title: Text("Home"),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.category),
              title: Text("Categories"),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.search),
              title: Text("Search"),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.shopping_cart),
              title: Text("Cart"),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.account_circle),
              title: Text("Profile"),
            ),
          ],
        ),
      ),
    );
  }
}