参数类型 'Widget Function(BuildContext, T, Widget)' 无法分配给参数类型 'Widget Function(BuildContext, T, Widget?)

Question

我有一个基本小部件 class，自从我将提供程序版本升级到 5.0.0 后它就不再工作了。

在 builder: widget.builder 我收到这个错误：

The argument type 'Widget Function(BuildContext, T, Widget)' can't be assigned to the parameter type 'Widget Function(BuildContext, T, Widget?)

我该如何解决这个问题？

这是我的代码

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

class BaseWidget<T extends ChangeNotifier> extends StatefulWidget {
  final Widget Function(BuildContext context, T model, Widget child) builder;
  final T model;
  final Widget child;
  final Function(T) onModelReady;

  BaseWidget({
    Key? key,
    required this.builder,
    required this.model,
    required this.child,
    required this.onModelReady,
  }) : super(key: key);

  _BaseWidgetState<T> createState() => _BaseWidgetState<T>();
}

class _BaseWidgetState<T extends ChangeNotifier> extends State<BaseWidget<T>> {
  late T model;

  @override
  void initState() {
    
    model = widget.model;

      widget.onModelReady(model);

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<T>(
      create: (context) => model,
      child: Consumer<T>(
        builder: widget.builder,
        child: widget.child,
      ),
    );
  }
}

Answer 1

我将代码粘贴到 Android studio 中，看起来需要更改以下内容：

来自

final Widget Function(BuildContext context, T model, Widget child) builder;

至

final Widget Function(BuildContext context, T model, Widget? child) builder;

参数类型 'Widget Function(BuildContext, T, Widget)' 无法分配给参数类型 'Widget Function(BuildContext, T, Widget?)

The argument type 'Widget Function(BuildContext, T, Widget)' can't be assigned to the parameter type 'Widget Function(BuildContext, T, Widget?)

flutter

flutter-provider