在flutter使用TabController過程中

TabController _tabController;

提示：
Non-nullable instance field '_tabController' must be initialized.
Try adding an initializer expression, or a generative constructor that initializes it, or mark it 'late'.如果_tabController是全局的變量男公，在之前的版本中是不報錯，看到報錯信息已經(jīng)提示了怎么修改磁携，添加修飾詞late氮唯，稍后初始化的意思鉴吹。
“Flutter Late就是Flutter的延遲執(zhí)行函數(shù),它被用來處理延遲執(zhí)行請求,以確保在特定時間之后才會執(zhí)行。這樣就解決報錯了您觉。
然后在initState（）方法中初始化

void initState() {
    super.initState();

    _tabController = TabController(length: 3, vsync: this);
  }

完整代碼：

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
      debugShowCheckedModeBanner: false,
      title: "TabBar Inside AppBar Demo",
      home: TopTabBarAppBarDemo(),
    ));

class TopTabBarAppBarDemo extends StatefulWidget {
  @override
  _TopTabBarAppBarDemoState createState() => _TopTabBarAppBarDemoState();
}

class _TopTabBarAppBarDemoState extends State<TopTabBarAppBarDemo>
    with SingleTickerProviderStateMixin {
  late TabController _tabController;

  @override
  void initState() {
    super.initState();

    _tabController = TabController(length: 3, vsync: this);
  }

  @override
  void dispose() {
    _tabController.dispose();
    super.dispose();
  }

  Widget getTabBar() {
    return TabBar(controller: _tabController, tabs: [
      Tab(text: "首頁", icon: Icon(Icons.home)),
      Tab(text: "編輯", icon: Icon(Icons.edit)),
      Tab(text: "設(shè)置", icon: Icon(Icons.settings)),
    ]);
  }

  Widget getTabBarPages() {
    return TabBarView(controller: _tabController, children: <Widget>[
      Container(
        color: Colors.red,
        child: Text("首頁",
            style: Theme.of(context) //
                .primaryTextTheme
                .titleLarge),
      ),
      Container(color: Colors.green),
      Container(color: Colors.blue)
    ]);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          flexibleSpace: SafeArea(
            child: getTabBar(),
          ),
        ),
        body: getTabBarPages());
  }
}

效果圖：

WeChat513cd35061bed215ca84064dbba033cb.png