位置参数过多导致堆栈错误答案

【问题标题】：Too many positional arguments flutter stack error位置参数过多导致堆栈错误
【发布时间】：2020-12-03 23:29:46
【问题描述】：

我有一个将文本放在图像上的堆栈，但是当我这样做时，我收到一条错误消息：位置参数过多：预期为 0，但找到了 3。它是一个计算器，用户的输出是 claculator.view.toString()。它背后的图像位于一个名为 assets 的文件中，名为 please.png。随时问我任何问题。 注意错误在第 19 行。

import 'package:google_fonts/google_fonts.dart';
import 'package:neumorphism_web/calculator/calculator_logic.dart';
import 'package:neumorphism_web/calculator/neu_calculator_button.dart';
import 'package:neumorphism_web/calculator/neumorphic_theme.dart';
import 'package:provider/provider.dart';
import 'image_banner.dart';

class CalculatorView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final calculator = Provider.of<Calculator>(context);
    return Material(
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 15.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.end,
          children: [
            Stack(
              Spacer(),
              ImageBanner("assets/please.png"),
              Text(
                calculator.value.toString(),
                style: GoogleFonts.montserrat(
                  fontSize: 75,
                  fontWeight: FontWeight.w700,
                  color: Colors.white,
                ),
              ),
              
            ),
            SizedBox(height: 50),
            ButtonRow(children: [
              NeuCalculatorButton(
                text: 'AC',
                onPressed: calculator.reset,
              ),
              NeuCalculatorButton(
                text: '+/-',
                onPressed: () {},
              ),
              NeuCalculatorButton(
                text: '%',
                onPressed: () {},
              ),
              NeuCalculatorButton(
                text: '÷',
                textColor: kOrange,
                textSize: 35,
                onPressed: calculator.divide,
                isChosen: calculator.currentVariable is CalculatorDivide,
              ),
            ]),
            ButtonRow(
              children: [
                NeuCalculatorButton(
                  text: '7',
                  onPressed: () => calculator.setValue(7),
                ),
                NeuCalculatorButton(
                  text: '8',
                  onPressed: () => calculator.setValue(8),
                ),
                NeuCalculatorButton(
                  text: '9',
                  onPressed: () => calculator.setValue(9),
                ),
                NeuCalculatorButton(
                  text: 'x',
                  textColor: kOrange,
                  onPressed: calculator.multiply,
                  isChosen: calculator.currentVariable is CalculatorMultiply,
                ),
              ],
            ),
            ButtonRow(
              children: [
                NeuCalculatorButton(
                  text: '4',
                  onPressed: () => calculator.setValue(4),
                ),
                NeuCalculatorButton(
                  text: '5',
                  onPressed: () => calculator.setValue(5),
                ),
                NeuCalculatorButton(
                  text: '6',
                  onPressed: () => calculator.setValue(6),
                ),
                NeuCalculatorButton(
                  text: '-',
                  textColor: kOrange,
                  textSize: 35,
                  onPressed: calculator.deduct,
                  isChosen: calculator.currentVariable is CalculatorDeduct,
                ),
              ],
            ),
            ButtonRow(
              children: [
                NeuCalculatorButton(
                  text: '1',
                  onPressed: () => calculator.setValue(1),
                ),
                NeuCalculatorButton(
                  text: '2',
                  onPressed: () => calculator.setValue(2),
                ),
                NeuCalculatorButton(
                  text: '3',
                  onPressed: () => calculator.setValue(3),
                ),
                NeuCalculatorButton(
                  text: '+',
                  textColor: kOrange,
                  textSize: 35,
                  onPressed: calculator.add,
                  isChosen: calculator.currentVariable is CalculatorAdd,
                ),
              ],
            ),
            ButtonRow(
              children: [
                NeuCalculatorButton(
                  text: '0',
                  onPressed: () => calculator.setValue(0),
                  isPill: true,
                ),
                NeuCalculatorButton(
                  text: '.',
                  onPressed: () {},
                ),
                NeuCalculatorButton(
                  text: '=',
                  textColor: kOrange,
                  textSize: 35,
                  onPressed: calculator.showResult,
                ),
              ],
            ),
            SizedBox(height: 15)
          ],
        ),
      ),
    );
  }
}

class ButtonRow extends StatelessWidget {
  const ButtonRow({
    Key key,
    @required this.children,
  }) : super(key: key);

  final List<NeuCalculatorButton> children;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: children,
      ),
    );
  }
}

【问题讨论】：

标签： image flutter dart text stack

【解决方案1】：

Stack 不接受任何位置参数。它采用 named children 参数，该参数采用 list:

Stack(children: [
  Spacer(),
  ImageBanner("assets/please.png"),
  ...
]),

【讨论】：

【解决方案2】：

您直接将小部件作为参数传递给Stack，这意味着您正在尝试为其提供位置参数，而堆栈不接受任何位置参数！

但是，Stack 采用命名参数 children，它采用 List，您可以使用它来将小部件放入！

Stack(
children: <Widget>[
    MyWidget(),
    Positioned(
        bottom: 20,
        left: 20,
        child: MyWidget2(color: Colors.blue),
    ),
    Positioned(
        top: 50,
        right: 50,
        child: MyWidget3(color: Colors.red)
    )
]

【讨论】：