无效的值：不在包容性范围0..4：5

Question

我遇到了奇怪的错误。我想为列表中的每个单元格创建一个小部件，但是当我编写“ itemCount：smindtitle.length”时，我会有那个红色屏幕。 即使我只输入1、2或任何int编号，

第二个问题也是我有一个时间选择器，但是当我要输出输出的数字时，它仅显示随机数，例如0分钟，30hrs

import 'dart:io';
import 'package:flutter/material.dart';
    void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(debugShowCheckedModeBanner: false,
        home: HomePage());
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  var RemindTitle = ["First", "Second", "Third", "Fourth", "sdf"],
      RemindText = ["TexttF", "TextS", "TextT", "TextFr", "sdf"];
  var Counter = -1;
  DateTime? date;
  TimeOfDay _time = TimeOfDay.now();
  var DateText = "Enter the date", ChosenTime = " ";

  bool AlreadyBuilt = false;

  Widget build(BuildContext context) {
    return Scaffold(
      body: ListView.builder(
          padding: EdgeInsets.all(20),
          itemCount: RemindTitle.length,
          itemBuilder: (BuildContext context, int index) {
            if(AlreadyBuilt == false) {
              AlreadyBuilt = true;
              return Row(
                children: [
                Expanded(
                flex: 4,
                child: Container(
                  height: 75,
                  child: ElevatedButton(
                    child: Center(
                      child: Text("Add Remind"),
                    ),
                    onPressed: () {
                      showModalBottomSheet<void>(
                          context: context,
                          builder: (BuildContext context) {
                            return Container(
                                child: Center(
                                  child: Column(children: [
                                    Row(
                                      children: [
                                        Padding(padding: EdgeInsets.all(10)),
                                        Expanded(
                                            child: ElevatedButton(
                                                onPressed: () async {
                                                  date = await showDatePicker(
                                                    context: context,
                                                    initialDate:
                                                    new DateTime.now(),
                                                    firstDate:
                                                    new DateTime(2015),
                                                    lastDate:
                                                    new DateTime(2030),
                                                  );
                                                },
                                                child: Text("Enter the date"))),
                                        Padding(padding: EdgeInsets.all(10)),
                                        Expanded(
                                            child: ElevatedButton(
                                                onPressed: () async {
                                                  showTimePicker(
                                                      context: context,
                                                      initialTime:
                                                      TimeOfDay.now())
                                                      .then((value) {
                                                    setState(() {
                                                      _time = value!;
                                                    });
                                                  });
                                                  if (date != null) {
                                                    ChosenTime =
                                                        "Chosen time: " +
                                                            date!.day
                                                                .toString() +
                                                            ":" +
                                                            date!.month
                                                                .toString() +
                                                            ":" +
                                                            date!.year
                                                                .toString() +
                                                            ", time: " + _time.minute.toString() +
                                                            ":" +
                                                            _time.hour
                                                                .toString();
                                                  }
                                                },
                                                child: Text("Enter the time"))),
                                        Padding(padding: EdgeInsets.all(10)),
                                      ],
                                    ),
                                    Padding(padding: EdgeInsets.all(10)),
                                    Text(ChosenTime)
                                  ]),
                                ));
                          });
                    },
                  ),
                ),
              ),
            Padding(padding: EdgeInsets.fromLTRB(10, 0, 0, 0)),
            Expanded(
            flex: 4,
            child: Container(
            height: 75,
            child: ElevatedButton(
            onPressed: () {},
            child: Center(
            child: Text("Delete Remind"),
            )),
            ),
            )
            ],
            );
            }

            if(Counter < RemindTitle.length){
              Counter++;
            }
              return Container(
                height: 130,
                width: 175,
                child: ElevatedButton(
                    onPressed: () {},
                    child: Center(
                      child: Column(
                        children: [
                          Padding(padding: EdgeInsets.fromLTRB(0, 10, 0, 10)),
                          Text(
                            RemindTitle[Counter],
                            style: TextStyle(fontSize: 20),
                          ),
                          Padding(padding: EdgeInsets.fromLTRB(0, 10, 0, 10)),
                          Text(RemindText[Counter])
                        ],
                      ),
                    )),
                padding: EdgeInsets.fromLTRB(0, 20, 0, 0),
              );
          }),
      appBar: AppBar(
        title: (Text("Reminder :)")),
        centerTitle: true,
      ),
    );
  }
}

红色屏幕

Answer 1

这是因为您的提示长度为5，您正在尝试访问第六项，而该项目不可用。时间也正确显示。但是，您首先显示会议分钟，而以24小时格式的小时和SETSTATE在模型中无法正常工作，显示您选择的任何时间，始终是您按下按钮的当前时间。

希望这能解决您的问题。

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
        debugShowCheckedModeBanner: false, home: const HomePage());
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<String> remindTitle = ["First", "Second", "Third", "Fourth", "sdf"],
      remindText = ["TexttF", "TextS", "TextT", "TextFr", "sdf"];
  int counter = -1;
  DateTime? date;
  TimeOfDay _time = TimeOfDay.now();
  String dateText = "Enter the date", chosenTime = "";
  bool alreadyBuilt = false;

  showDateTime() {
    if (date != null) {
      int hour = _time.hour > 12
          ? _time.hour - 12
          : _time.hour;
      String meridian =
      _time.hour > 12
          ? "PM"
          : "AM";
      chosenTime =
      "Chosen Date: ${date!.day}:${date!.month < 10 ? '0' : ''}${date!.month}:${date!.year}, time: ${hour < 10 ? '0' : ''}$hour:${_time.minute} $meridian";
      setState((){});
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: [
          Container(
            padding: const EdgeInsets.fromLTRB(20, 20, 20, 0),
            height: 100,
            child: Row(
              children: [
                Expanded(
                  flex: 4,
                  child: SizedBox(
                    height: 75,
                    child: ElevatedButton(
                      child: const Center(
                        child: Text("Add Remind"),
                      ),
                      onPressed: () {
                        showModalBottomSheet<void>(
                            context: context,
                            builder: (BuildContext context) {
                              return Center(
                                child: Column(children: [
                                  Row(
                                    children: [
                                      const Padding(
                                          padding: EdgeInsets.all(10)),
                                      Expanded(
                                          child: ElevatedButton(
                                              onPressed: () async {
                                                date = await showDatePicker(
                                                  context: context,
                                                  initialDate: DateTime.now(),
                                                  firstDate: DateTime(2015),
                                                  lastDate: DateTime(2030),
                                                );
                                                showDateTime();
                                              },
                                              child: const Text(
                                                  "Enter the date"))),
                                      const Padding(
                                          padding: EdgeInsets.all(10)),
                                      Expanded(
                                          child: ElevatedButton(
                                              onPressed: () async {
                                                showTimePicker(
                                                        context: context,
                                                        initialTime:
                                                            TimeOfDay.now())
                                                    .then((value) {
                                                  _time = value!;
                                                  showDateTime();
                                                });
                                              },
                                              child: const Text(
                                                  "Enter the time"))),
                                      const Padding(
                                          padding: EdgeInsets.all(10)),
                                    ],
                                  ),
                                  const Padding(padding: EdgeInsets.all(10)),
                                  Text(chosenTime)
                                ]),
                              );
                            });
                      },
                    ),
                  ),
                ),
                const Padding(padding: EdgeInsets.fromLTRB(10, 0, 0, 0)),
                Expanded(
                  flex: 4,
                  child: SizedBox(
                    height: 75,
                    child: ElevatedButton(
                        onPressed: () {},
                        child: const Center(
                          child: Text("Delete Remind"),
                        )),
                  ),
                )
              ],
            ),
          ),
          Expanded(
            flex: 1,
            child: ListView.builder(
                padding: const EdgeInsets.all(20),
                itemCount: remindTitle.length,
                itemBuilder: (BuildContext context, int index) {
                  return Container(
                    height: 130,
                    width: 175,
                    padding: const EdgeInsets.fromLTRB(0, 20, 0, 0),
                    child: ElevatedButton(
                        onPressed: () {},
                        child: Center(
                          child: Column(
                            children: [
                              const Padding(
                                  padding: EdgeInsets.fromLTRB(0, 10, 0, 10)),
                              Text(
                                remindTitle[index],
                                style: const TextStyle(fontSize: 20),
                              ),
                              const Padding(
                                  padding: EdgeInsets.fromLTRB(0, 10, 0, 10)),
                              Text(remindText[index])
                            ],
                          ),
                        )),
                  );
                }),
          ),
        ],
      ),
      appBar: AppBar(
        title: (const Text("Reminder :)")),
        centerTitle: true,
      ),
    );
  }
}