将 StatefulWidget 数据传递给 State 类而不使用构造函数

Posted 2023-02-23

【中文标题】将 StatefulWidget 数据传递给 State 类而不使用构造函数

【英文标题】：Pass StatefulWidget data to the State class without using constructor

【发布时间】：2018-10-29 22:06:59

【问题描述】：

我设法通过如下构造函数将 Stateful 类变量的值传递给 State 类：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return MaterialApp(
        title: 'Demo',
        home: MyHomePage('John', 'Morison'),
    );
  


class MyHomePage extends StatefulWidget 
  MyHomePage(this.fname, this.lname);

  final String fname;
  final String lname;

  @override
  _MyHomePageState createState() => _MyHomePageState(fname, lname);


class _MyHomePageState extends State<MyHomePage> 
  _MyHomePageState(this.fname, this.lname);

  final String fname;
  final String lname;

  @override
  Widget build(BuildContext context) 
    return Scaffold(
      body: Center(
        child: Text('Hello $fname $lname'),
      )
    );
  

这很奇怪，因为变量不止两个，我不得不做很多工作。有没有更好的办法？

【参考方案1】：

是的，有widget：

来自文档：

  /// 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;

代码应如下所示：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return MaterialApp(
        title: 'Demo',
        home: MyHomePage('John', 'Morison'),
    );
  


class MyHomePage extends StatefulWidget 
  MyHomePage(this.fname, this.lname);

  final String fname;
  final String lname;

  @override
  _MyHomePageState createState() => _MyHomePageState();


class _MyHomePageState extends State<MyHomePage> 

  @override
  Widget build(BuildContext context) 
    return Scaffold(
      body: Center(
        child: Text('Hello $widget.fname $widget.lname'),
      )
    );
  

【讨论】：

我一点也不明白。您将状态存储在小部件中，并将 UI 构建存储在状态中。这与对象的命名方式完全相反。