Flutter备忘录: 《State----之浅析理解StatefulWidget、BuildContext、StatefulElement与生命周期的关系》

//platform: Android
//author: 'mulegame'

import 'package:flutter/material.dart';

class TabNavigator extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _TabNavigator();

}
// abstract class State<T extends StatefulWidget> with Diagnosticable{...}
class _TabNavigator extends State<TabNavigator> {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
  }

}

重点1:

@override
  State<StatefulWidget> createState() => _TabNavigator();

抛砖引玉: 为什么在TabNavigator中必须要重写(@override)State中的createState()?

查看State抽象类源码时发现:

abstract class State<T extends StatefulWidget> with Diagnosticable {
  /// The current configuration.
  ///
  /// A [State] object's configuration is the corresponding [StatefulWidget]
  /// instance. This property is initialized by the framework before calling
  /// [initState]. If the parent updates this location in the tree to a new
  /// widget with the same [runtimeType] and [Widget.key] as the current
  /// configuration, the framework will update this property to refer to the new
  /// widget and then call [didUpdateWidget], passing the old configuration as
  /// an argument.
  T get widget => _widget!;
  T? _widget;

  /// The current stage in the lifecycle for this state object.
  ///
  /// This field is used by the framework when asserts are enabled to verify
  /// that [State] objects move through their l