Flutter：在setstate之后将数据保留在文本字段中

Question

1. 我有一个文本字段数组。
2. 向数组添加新文本字段的按钮。
3. 如果您将数据添加到文本字段并通过单击添加按钮添加新元素，则添加的数据将消失。
4. 按钮函数中有一个 setstate，用于查看数组中的新元素。
5. 如何向数组中添加新元素，将旧数据保留在文本字段中？

start_workout.dart

    import 'package:flutter/material.dart';
import 'package:fultter_ultralifestyle/src/models/models.dart' show SetModel;
import 'package:fultter_ultralifestyle/src/presentation/widgets/dynamic_widget.dart';

class WorkoutStartScreen extends StatefulWidget {
  static const String routeName = "workoutStart";
  @override
  _WorkoutStartScreenState createState() => _WorkoutStartScreenState();
}

class _WorkoutStartScreenState extends State<WorkoutStartScreen> {
  final List<SetModel> sets = [
  ];

  void _addSet() {
    final id = sets.length;
    sets.add(SetModel(id: id, pounds: 0, reps: 0));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Workout tracker"),
        centerTitle: true,
      ),
      body: Container(
        child: Column(
          children: <Widget>[
            Expanded(
              child: ListView.builder(
                  itemCount: sets.length,
                  itemBuilder: (BuildContext context, int index) {
                    return DynamicWidget(
                      set: sets[index],
                      pos: index +1,
                      delete: () {
                        sets.removeAt(index);
                        setState(() {});
                      },
                    );
                  }),
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _addSet(),
        child: Icon(Icons.add),
      ),
    );
  }
}

dynamic_widget.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:fultter_ultralifestyle/src/models/models.dart';
import 'package:fultter_ultralifestyle/src/presentation/widgets/text_widget.dart';

class DynamicWidget extends StatelessWidget {
  final TextEditingController poundsController = TextEditingController();
  final TextEditingController repsController = TextEditingController();

  final SetModel set;
  final int pos;
  Function delete;

  DynamicWidget({
    Key key,
    @required this.set,
    @required this.pos,
    @required this.delete,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final Size size = MediaQuery.of(context).size;

    return Container(
      child: Column(
        children: <Widget>[
          Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                child: text(
                  caption: "SET $pos",
                ),
              ),
              SizedBox(width: 20.0),
              Container(
                width: size.width / 4,
                child: Column(
                  children: <Widget>[
                    TextField(
                      controller: poundsController,
                      keyboardType: TextInputType.number,
                      inputFormatters: [
                        WhitelistingTextInputFormatter.digitsOnly,
                      ],
                    ),
                    SizedBox(height: 10),
                    text(caption: "pounds".toUpperCase()),
                  ],
                ),
              ),
              SizedBox(
                width: 20,
              ),
              text(caption: "X"),
              SizedBox(
                width: 20,
              ),
              Container(
                width: size.width / 4,
                child: Column(
                  children: <Widget>[
                    TextField(
                      controller: repsController,
                      keyboardType: TextInputType.number,
                      inputFormatters: [
                        WhitelistingTextInputFormatter.digitsOnly
                      ],
                    ),
                    SizedBox(height: 10),
                    text(caption: "reps".toUpperCase()),
                  ],
                ),
              ),
              SizedBox(width: 5.0),
              IconButton(
                icon: Icon(Icons.delete_forever),
                onPressed: delete,
              )
            ],
          ),
        ],
      ),
    );
  }
}

Answer 1

我通过在您的文本字段中的文本更改时更新您的SetModel 来解决这个问题。主要部分是动态小部件文本字段中的updatePounds 和updateReps 方法以及onChanged 方法。

我还确保在构建动态小部件时使用 SetModel 中包含的值初始化控制器。

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

void main() {
  runApp(MaterialApp(
    home: WorkoutStartScreen(),
  ));
}

class SetModel {
  final int id;
  int pounds;
  int reps;

  SetModel({
    this.id,
    this.pounds,
    this.reps,
  });

  void updatePounds(int pounds) {
    this.pounds = pounds;
  }

  void updateReps(int reps) {
    this.reps = reps;
  }
}

class WorkoutStartScreen extends StatefulWidget {
  static const String routeName = "workoutStart";
  @override
  _WorkoutStartScreenState createState() => _WorkoutStartScreenState();
}

class _WorkoutStartScreenState extends State<WorkoutStartScreen> {
  final List<SetModel> sets = [];

  void _addSet() {
    final id = sets.length;
    setState(() {
      sets.add(SetModel(id: id, pounds: 0, reps: 0));
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Workout tracker"),
        centerTitle: true,
      ),
      body: Container(
        child: Column(
          children: <Widget>[
            Expanded(
              child: ListView.builder(
                itemCount: sets.length,
                itemBuilder: (BuildContext context, int index) {
                  return DynamicWidget(
                    set: sets[index],
                    pos: index + 1,
                    delete: () {
                      setState(() {
                        sets.removeAt(index);
                      });
                    },
                  );
                },
              ),
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _addSet(),
        child: Icon(Icons.add),
      ),
    );
  }
}

class DynamicWidget extends StatelessWidget {
  final TextEditingController poundsController = TextEditingController();
  final TextEditingController repsController = TextEditingController();

  final SetModel set;
  final int pos;
  final Function delete;

  DynamicWidget({
    Key key,
    @required this.set,
    @required this.pos,
    @required this.delete,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final Size size = MediaQuery.of(context).size;

    if (set.pounds != 0) {
      poundsController.text = set.pounds.toString();
    }

    if (set.reps != 0) {
      repsController.text = set.reps.toString();
    }

    return Container(
      child: Column(
        children: <Widget>[
          Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                child: Text(
                  "SET $pos",
                ),
              ),
              SizedBox(width: 20.0),
              Container(
                width: size.width / 4,
                child: Column(
                  children: <Widget>[
                    TextField(
                      controller: poundsController,
                      onChanged: (String pounds) {
                        set.updatePounds(int.parse(pounds));
                      },
                      keyboardType: TextInputType.number,
                      inputFormatters: [WhitelistingTextInputFormatter.digitsOnly],
                    ),
                    SizedBox(height: 10),
                    Text("pounds".toUpperCase()),
                  ],
                ),
              ),
              SizedBox(
                width: 20,
              ),
              Text("X"),
              SizedBox(
                width: 20,
              ),
              Container(
                width: size.width / 4,
                child: Column(
                  children: <Widget>[
                    TextField(
                      controller: repsController,
                      onChanged: (String reps) {
                        set.updateReps(int.parse(reps));
                      },
                      keyboardType: TextInputType.number,
                      inputFormatters: [WhitelistingTextInputFormatter.digitsOnly],
                    ),
                    SizedBox(height: 10),
                    Text("reps".toUpperCase()),
                  ],
                ),
              ),
              SizedBox(width: 5.0),
              IconButton(
                icon: Icon(Icons.delete_forever),
                onPressed: delete,
              )
            ],
          ),
        ],
      ),
    );
  }
}

基本上，每次您从其父级调用setState 时，都会重新绘制动态小部件。由于您从未告诉动态小部件保存任何内容，因此它们会从头开始重绘。这种情况仍在发生，只是现在我们向他们提供了一些初始信息。

Here 是它工作的视频。

Answer 2

使用控制器！

TextEditingController password = new TextEditingController();

TextFormField(
                  validator: (value) {
                    if (value.isEmpty) {
                      return "Could not be empty";
                    }
                    return null;
                  },

                  enabled: !isLoading,
                  controller: password,
                  obscureText: hidePassword,
                  decoration: InputDecoration(
                    suffix: IconButton(icon: Icon((hidePassword)?Icons.remove_red_eye:Icons.cancel),onPressed: () => setState(() => hidePassword = !hidePassword),),
                      labelText: "PASSWORD",
                      border: OutlineInputBorder(
                          borderRadius: BorderRadius.circular(20))),
                  onFieldSubmitted: (String p) {
                    buttonPressed();
                  },
                ),

然后使用

检索它

var pass = username.text;

显然你可以使用一个控制器数组然后检索它们

Answer 3

我的技巧是让TextField 具有autofocus: true, 和onChange(lock) => lock = true 的属性

然后在运行 initState 或构建小部件时，我们使用 if (lock == false) 设置数据 setALLYourDataInController

代码：

bool lock = false;

Widget build(BuildContext context) {
...
if (lock == false) {
      firstNameController.text = detail?.firstName.toString() ?? '';
}
...
    }

我的TextField

TextField(
              autofocus: true,
              style: kTextFieldTextStyle,
              decoration: kInputDecoration.copyWith(
                hintText: 'Yogithesymbian',
                prefixIcon: Icon(Icons.person_add),
                suffixIcon: firstNameController.text.isNotEmpty
                    ? IconButton(
                        onPressed: firstNameController.clear,
                        icon: Icon(
                          Icons.clear,
                          color: kPrimaryColorLight,
                        ),
                      )
                    : null,
              ),
              onChanged: (unuse) {
                lock = true; // here is logic
                // set.updatePounds(int.parse(pounds));
              },
              textInputAction: TextInputAction.next,
              controller: firstNameController,
            ),