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在 Flutter 中获取值 TextEditingController 错误

分类：编程问答

如何解决在 Flutter 中获取值 TextEditingController 错误

我想用循环从textEditingController中取值，listview不滚动时出现的问题会导致报错“RangeError (index): Invalid value: Not in inclusive range 0..23: 24 "，我有 40 条记录的随机数据， 滚动到行尾时，应用程序将正常运行。我希望即使我不向下滚动数据仍然可以无错误地检索。

Error Log

你可以运行我的示例代码，请帮助我谢谢。

import 'dart:math';
import 'package:Flutter/material.dart';

class Karyawan {
  int id;
  String nama;
  int jamKerja;

  Karyawan({this.id,this.nama,});

  Karyawan.fromJson(Map<String,dynamic> json) {
    id = json['id'];
    nama = json['nama_karyawan'];
    jamKerja = json['jam_kerja'];
  }

  Map<String,dynamic> toJson() {
    final Map<String,dynamic> data = new Map<String,dynamic>();
    data['id'] = this.id;
    data['nama_karyawan'] = this.nama;
    data['jam_kerja'] = this.jamKerja;
    return data;
  }
}

List<Karyawan> _daftarKaryawan = List.generate(
  40,(index) => Karyawan(
    id: Random().nextInt(100),nama: 'test ${Random().nextInt(100)}',),);

class FormInputAbsenV3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Entry Absen"),body: FormEntry(listKaryawan:_daftarKaryawan)

    );
  }
}

class FormEntry extends StatefulWidget {
  final List<Karyawan> listKaryawan;
  const FormEntry({Key key,this.listKaryawan}) : super(key: key);
  @override
  _FormEntryState createState() => _FormEntryState();
}

class _FormEntryState extends State<FormEntry> {
  List karyawan = [];
  final _formKey = GlobalKey<FormState>();
  List<TextEditingController> _brutos = new List();
  List<TextEditingController> _nettos = new List();
  
  void addlistAbsen() {
    for (int i = 0; i < widget.listKaryawan.length; i++) {
      karyawan.add({
        "id": widget.listKaryawan[i].id,"bruto": _brutos[i].text,"netto": _nettos[i].text
      });
    }
    print(karyawan);
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        margin: EdgeInsets.all(5.0),child: Form(
          key: _formKey,child: Container(
            child: ListView.builder(
              itemCount: widget.listKaryawan.length,itemBuilder: (context,index) {
                _brutos.add(new TextEditingController());
                _nettos.add(new TextEditingController());
                return Column(
                  children: [
                    FormWidget(
                      index: index,nama: widget.listKaryawan[index].nama,brucon: _brutos[index],netcon: _nettos[index],SizedBox(
                      height: 20.0,],);
              },floatingActionButton: FloatingActionButton.extended(
        icon: Icon(Icons.save),label: Text("Save"),onpressed: () {
          if (_formKey.currentState.validate()) {
             addlistAbsen();
          }
        },);
  }
}

class FormWidget extends StatelessWidget {
  final int index;
  final String nama;
  final brucon;
  final netcon;
  FormWidget({this.index,this.brucon,this.netcon});
  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,children: [
        Expanded(
          child: Text("${index + 1}. ${nama}"),Expanded(
          child: TextFormField(
            decoration: new Inputdecoration(
              labelText: "Bruto",fillColor: Colors.white,border: new OutlineInputBorder(
                borderRadius: new BorderRadius.circular(25.0),borderSide: new BorderSide(),style: new TextStyle(
              fontFamily: "Poppins",controller: brucon,SizedBox(
          width: 20.0,Expanded(
            child: TextFormField(
              decoration: new Inputdecoration(
                labelText: "Netto",border: new OutlineInputBorder(
                  borderRadius: new BorderRadius.circular(25.0),style: new TextStyle(
                fontFamily: "Poppins",controller: netcon,))
      ],);
  }
}

解决方法

请在 initState 期间初始化您的 TextEditingController。

  @override
  void initState() {
    super.initState();
    for (int i = 0; i < widget.listKaryawan.length; i++) {
      _brutos.add(new TextEditingController());
      _nettos.add(new TextEditingController());
    }
  }

然后，删除 itemBuilder 中的这些行...

_brutos.add(new TextEditingController());
_nettos.add(new TextEditingController());

注意：当要重新显示/新显示列表项时，将调用 itemBuilder。因此，您的 TextEditingControllers 列表 > 列表项。 （尝试滚动到最底部，然后向上滚动）

,

您不能为此使用ListView.builder，您将不得不使用ListView。您不能使用 ListView.builder 构造函数，因为只为那些实际可见的子元素调用构建器。请参阅 ListView.builder 的文档

ListView.builder 构造函数

创建一个可滚动的线性小部件数组，这些小部件是在 需求。

此构造函数适用于具有大（或 无限) 孩子的数量，因为构建器只被调用 那些实际可见的孩子。

请看下面的代码：

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

final Color darkBlue = const Color.fromARGB(255,18,32,47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      //theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),debugShowCheckedModeBanner: false,home: Scaffold(
        body: Center(
          child: FormInputAbsenV3(),),);
  }
}

class Karyawan {
  int id;
  String nama;
  int jamKerja;

  Karyawan({
    this.id,this.nama,});

  Karyawan.fromJson(Map<String,dynamic> json) {
    id = json['id'];
    nama = json['nama_karyawan'];
    jamKerja = json['jam_kerja'];
  }

  Map<String,dynamic> toJson() {
    final Map<String,dynamic> data = Map<String,dynamic>();
    data['id'] = this.id;
    data['nama_karyawan'] = this.nama;
    data['jam_kerja'] = this.jamKerja;
    return data;
  }
}

List<Karyawan> _daftarKaryawan = List.generate(
  40,(index) => Karyawan(
    id: Random().nextInt(100),nama: 'test ${Random().nextInt(100)}',);

class FormInputAbsenV3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Entry Absen"),body: FormEntry(listKaryawan: _daftarKaryawan));
  }
}

class FormEntry extends StatefulWidget {
  final List<Karyawan> listKaryawan;
  const FormEntry({Key key,this.listKaryawan}) : super(key: key);
  @override
  _FormEntryState createState() => _FormEntryState();
}

class _FormEntryState extends State<FormEntry> {
  List karyawan = [];
  final _formKey = GlobalKey<FormState>();
  List<TextEditingController> _brutos = [];
  List<TextEditingController> _nettos = [];

  @override
  void initState() {
    super.initState();
    for (int i = 0; i < widget.listKaryawan.length; i++) {
      _brutos.add(TextEditingController());
      _nettos.add(TextEditingController());
    }
  }

  void addlistAbsen() {
    for (int i = 0; i < widget.listKaryawan.length; i++) {
      karyawan.add({
        "id": widget.listKaryawan[i].id,"bruto": _brutos[i].text,"netto": _nettos[i].text
      });
    }
    print(karyawan);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        margin: EdgeInsets.all(5.0),child: Form(
          key: _formKey,child: Container(
            // child: ListView.builder(
            //   itemCount: widget.listKaryawan.length,//   itemBuilder: (context,index) {
            //     _brutos.add(new TextEditingController());
            //     _nettos.add(new TextEditingController());
            //     return Column(
            //       children: [
            //         FormWidget(
            //           index: index,//           nama: widget.listKaryawan[index].nama,//           brucon: _brutos[index],//           netcon: _nettos[index],//         ),//         SizedBox(
            //           height: 20.0,//       ],//     );
            //   },// ),child: ListView(
              children: [
                for (int index = 0; index < widget.listKaryawan.length; index++)
                  Column(
                    children: [
                      FormWidget(
                        index: index,nama: widget.listKaryawan[index].nama,brucon: _brutos[index],netcon: _nettos[index],SizedBox(
                        height: 20.0,],floatingActionButton: FloatingActionButton.extended(
        icon: Icon(Icons.save),label: Text("Save"),onPressed: () {
          if (_formKey.currentState.validate()) {
            addlistAbsen();
          }
        },);
  }
}

class FormWidget extends StatelessWidget {
  final int index;
  final String nama;
  final TextEditingController brucon;
  final TextEditingController netcon;
  const FormWidget({this.index,this.brucon,this.netcon});
  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,children: [
        Expanded(
          child: Text("${index + 1}. ${nama}"),Expanded(
          child: TextFormField(
            decoration: InputDecoration(
              labelText: "Bruto",fillColor: Colors.white,border: OutlineInputBorder(
                borderRadius: BorderRadius.circular(25.0),borderSide: BorderSide(),style: TextStyle(
              fontFamily: "Poppins",controller: brucon,SizedBox(
          width: 20.0,Expanded(
            child: TextFormField(
          decoration: InputDecoration(
            labelText: "Netto",border: OutlineInputBorder(
              borderRadius: BorderRadius.circular(25.0),style: TextStyle(
            fontFamily: "Poppins",controller: netcon,))
      ],);
  }
}

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