不使用构造函数将StatefulWidget数据传递给State类

Z时代
2024-01-10
分类：问答

我设法通过构造函数将Stateful类变量的值传递给State类，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(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'),
      )
    );
  }
}

太奇怪了，因为有两个以上的变量，所以我不得不做很多工作。有没有更好的办法？

回答：

是的，有widget：

从文档：

>       /// 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}'),
          )
        );
      }
    }