引數型別“功能？”不能分配給引數型別“voidFunction(String)?”。這段代碼有修復嗎？

任何人都知道對此的修復，我不斷收到此錯誤，我在這里使用了 OnPressed，我想我想在這里使用 VoidCallback 但是當我使用它時，我得到了錯誤：

“引數型別 'void Function(dynamic)' 不能分配給引數型別 'void Function()'。”

一直在這個問題上感謝您的幫助。

import 'package:concept1/constant.dart';
import 'package:concept1/screen/login/widget/welcome_back.dart';
import 'package:flutter/material.dart';

class LoginScreen extends StatelessWidget {
  const LoginScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: buildAppBar(context),
      body: Column(
        children: [
          const WelcomeBack(),
          Container(
            padding: EdgeInsets.symmetric(vertical: 20, horizontal: 30),
            child: Column(children: <Widget>[
              InputTextField(
                label: 'Email',
                onChange: (value) {},
              ),
              InputTextField(
                label: 'Password',
                onChange: (value) {},
              ),
            ]),
          )
        ],
      ),
    );
  }

  AppBar buildAppBar(BuildContext context) {
    return AppBar(
      backgroundColor: mBackgroundColor,
      elevation: 0,
      centerTitle: true,
      title: Text(
        'Login Screen',
        style: TextStyle(
          color: mPrimaryColor,
        ),
      ),
      leading: IconButton(
        icon: const Icon(Icons.arrow_back_ios),
        color: mPrimaryColor,
        onPressed: () {
          Navigator.pop(context);
        },
      ),
    );
  }
}

class InputTextField extends StatelessWidget {
  const InputTextField({
    Key? key,
    required this.label,
    required this.onChange,
  }) : super(key: key);

  final String label;
  final Function? onChange;

  @override
  Widget build(BuildContext context) {
    return TextField(
      onChanged: onChange,
      cursorColor: Colors.grey,
      decoration: InputDecoration(
          labelText: label,
          labelStyle: const TextStyle(color: Colors.grey),
          border: UnderlineInputBorder(
              borderSide: BorderSide(
            color: mPrimaryColor,
            width: 2,
          )),
          focusedBorder: UnderlineInputBorder(
              borderSide: BorderSide(
            color: mPrimaryColor,
            width: 2,
          )),
          enabledBorder: const UnderlineInputBorder(
              borderSide: BorderSide(
            color: Colors.grey,
            width: 0.5,
          ))),
    );
  }
}

uj5u.com熱心網友回復：

每當您將函式作為引數傳遞時，您應該使用VoidCallBack而不是Function

只是改變 ：

final Function? onChange

至

final VoidCallBack? onChange

uj5u.com熱心網友回復：

我想到了！

    import 'package:concept1/constant.dart';
import 'package:concept1/screen/login/widget/welcome_back.dart';
import 'package:flutter/material.dart';

class LoginScreen extends StatelessWidget {
  const LoginScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: buildAppBar(context),
      body: Column(
        children: [
          const WelcomeBack(),
          Container(
            padding: EdgeInsets.symmetric(vertical: 20, horizontal: 30),
            child: Column(children: <Widget>[
              InputTextField(
                label: 'Email',
                onChange: () {},
              ),
              InputTextField(
                label: 'Password',
                onChange: (() {}),
              )
            ]),
          )
        ],
      ),
    );
  }

  AppBar buildAppBar(BuildContext context) {
    return AppBar(
      backgroundColor: mBackgroundColor,
      elevation: 0,
      centerTitle: true,
      title: Text(
        'Login Screen',
        style: TextStyle(
          color: mPrimaryColor,
        ),
      ),
      leading: IconButton(
        icon: const Icon(Icons.arrow_back_ios),
        color: mPrimaryColor,
        onPressed: () {
          Navigator.pop(context);
        },
      ),
    );
  }
}

class InputTextField extends StatelessWidget {
  const InputTextField({
    Key? key,
    required this.label,
    required this.onChange,
  }) : super(key: key);

  final String label;
  final VoidCallback onChange;

  @override
  Widget build(BuildContext context) {
    return TextField(
      onChanged: (value) {},
      cursorColor: Colors.grey,
      decoration: InputDecoration(
          labelText: label,
          labelStyle: const TextStyle(color: Colors.grey),
          border: UnderlineInputBorder(
              borderSide: BorderSide(
            color: mPrimaryColor,
            width: 2,
          )),
          focusedBorder: UnderlineInputBorder(
              borderSide: BorderSide(
            color: mPrimaryColor,
            width: 2,
          )),
          enabledBorder: const UnderlineInputBorder(
              borderSide: BorderSide(
            color: Colors.grey,
            width: 0.5,
          ))),
    );
  }
}

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