如何正确预填充颤振表单字段？

Question

我正在尝试创建一个“编辑个人资料”页面，在该页面中加载所有用户数据并让用户对其进行修改。但是，同时使用TextEditingController 上的value 和text 属性会导致无法修改TextFormField 中的数据。我可以添加到它的开头，但我不能从中删除任何字符。

为了进一步详细说明这种行为，在下面的屏幕截图中，我可以在字段中输入更多内容（就像我输入“Asdf”一样），但是从光标所在的位置开始，我无法将光标向右移动或删除"F" 或任何原本放置在那里的字符。

在TextFormField 的OnSaved 函数中，value 参数是提交时表单的全文，在本例中为“AsdfFrederick”。

这是我的代码：

import 'dart:async';
import 'package:flutter/material.dart';
import '../models/user.dart';

class EditProfileView extends StatefulWidget {
  @override
  _EditProfileViewState createState() => new _EditProfileViewState();
}

class _EditProfileViewState extends State<EditProfileView> {
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();

  void _handleSubmitted() {
    final FormState form = _formKey.currentState;
    if (!form.validate()) {
    } else {
      form.save();
      User.instance.save().then((result) {
        print("Saving done: ${result}.");
        Navigator.pop(context);
      });
    }
  }


  @override
  Widget build(BuildContext context) {
    final ThemeData themeData = Theme.of(context);
    final DateTime today = new DateTime.now();

    // controllers for form text controllers
    final TextEditingController _firstNameController =
        new TextEditingController();
    //_firstNameController.value = new TextEditingValue(text: User.instance.first_name);
    _firstNameController.text = User.instance.first_name;
    final TextEditingController _lastNameController =
        new TextEditingController();
    _lastNameController.text = User.instance.last_name;

    return new Scaffold(
        appBar: new AppBar(title: const Text('Edit Profile'), actions: <Widget>[
          new Container(
              padding: const EdgeInsets.fromLTRB(0.0, 10.0, 5.0, 10.0),
              child: new MaterialButton(
                color: themeData.primaryColor,
                textColor: themeData.secondaryHeaderColor,
                child: new Text('Save'),
                onPressed: () {
                  _handleSubmitted();
                  Navigator.pop(context);
                },
              ))
        ]),
        body: new Form(
            key: _formKey,
            autovalidate: _autovalidate,
            onWillPop: _warnUserAboutInvalidData,
            child: new ListView(
              padding: const EdgeInsets.symmetric(horizontal: 16.0),
              children: <Widget>[
                new Container(
                  child: new TextFormField(
                    decoration: const InputDecoration(labelText: "First Name", hintText: "What do people call you?"),
                    autocorrect: false,
                    controller: _firstNameController,
                    onSaved: (String value) {
                      User.instance.first_name = value;
                    },
                  ),
                ),
                new Container(
                  child: new TextFormField(
                    decoration: const InputDecoration(labelText: "Last Name"),
                autocorrect: false,
                controller: _lastNameController,
                onSaved: (String value) {
                  User.instance.last_name = value;
                },
              ),
            ),
          ],
        )));
  }
}

这里是flutter doctor：

% flutter doctor
[✓] Flutter (on Mac OS X 10.12.6 16G29, locale en-US, channel alpha)
    • Flutter at /Users/frederickcook/flutter
    • Framework revision 701d534ba9 (2 weeks ago), 2017-09-12 14:01:51 -0700
    • Engine revision 31d03de019
    • Tools Dart version 1.25.0-dev.11.0

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.0)
    • Android SDK at /Users/frederickcook/Library/Android/sdk
    • Platform android-26, build-tools 26.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.0)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 9.0, Build version 9A235
    • ios-deploy 1.9.2
    • CocoaPods version 1.2.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] IntelliJ IDEA Community Edition (version 2017.2.5)
    • Flutter plugin version 17.0
    • Dart plugin version 172.4155.35

[✓] Connected devices
    • iPhone 7 • 2AE532E3-5B4B-4D8D-8CFB-F54C3BF6F8EE • ios • iOS 11.0 (simulator)

Answer 1

使用initialValue: 属性可以很好地与TextFormField 配合使用。

Answer 2

想通了：从TextFormField 切换到TextField，创建局部变量来存储对字段的更改，并使用initState 设置初始表单值，而不是在build 中进行。

import 'dart:async';
import 'package:flutter/material.dart';
import '../models/user.dart';

class EditProfileView extends StatefulWidget {
  @override
  _EditProfileViewState createState() => new _EditProfileViewState();
}

class _EditProfileViewState extends State<EditProfileView> {
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();

  void _handleSubmitted() {
    final FormState form = _formKey.currentState;
    if (!form.validate()) {
      _autovalidate = true; // Start validating on every change.
      showInSnackBar('Please fix the errors in red before submitting.');
    } else {
      showInSnackBar('snackchat');
      User.instance.first_name = firstName;
      User.instance.last_name = lastName;

      User.instance.save().then((result) {
        print("Saving done: ${result}.");
      });
    }
  }

  // controllers for form text controllers
  final TextEditingController _firstNameController = new TextEditingController();
  String firstName = User.instance.first_name;
  final TextEditingController _lastNameController = new TextEditingController();
  String lastName = User.instance.last_name;

  @override
  void initState() {
    _firstNameController.text = firstName;
    _lastNameController.text = lastName;
    return super.initState();
  }

  @override
  Widget build(BuildContext context) {
    final ThemeData themeData = Theme.of(context);
    final DateTime today = new DateTime.now();

    return new Scaffold(
        appBar: new AppBar(title: const Text('Edit Profile'), actions: <Widget>[
          new Container(
              padding: const EdgeInsets.fromLTRB(0.0, 10.0, 5.0, 10.0),
              child: new MaterialButton(
                color: themeData.primaryColor,
                textColor: themeData.secondaryHeaderColor,
                child: new Text('Save'),
                onPressed: () {
                  _handleSubmitted();
                  Navigator.pop(context);
                },
              ))
        ]),
        body: new Form(
            key: _formKey,
            autovalidate: _autovalidate,
            onWillPop: _warnUserAboutInvalidData,
            child: new ListView(
              padding: const EdgeInsets.symmetric(horizontal: 16.0),
              children: <Widget>[
                new Container(
                  child: new TextField(
                    decoration: const InputDecoration(labelText: "First Name", hintText: "What do people call you?"),
                    autocorrect: false,
                    controller: _firstNameController,
                    onChanged: (String value) {
                      firstName = value;
                    },
                  ),
                ),
                new Container(
                  child: new TextField(
                    decoration: const InputDecoration(labelText: "Last Name"),
                    autocorrect: false,
                    controller: _lastNameController,
                    onChanged: (String value) {
                      lastName = value;
                    },
                  ),
                ),
              ],
            )));
  }
}

Answer 3

TextFormField 具有 initialValue 属性。

要使用 TextField 完成此操作，您可以使用 控制器 来设置初始值：

final _controllerFirstName = TextEditingController();

_controllerFirstName.text = 'First Name here';

TextField(
  controller: _controllerFirstName,
  onChanged: (nameVal) => setState(() {
    _displayName = nameVal;
  }),
),

// to clear the controller
_controllerFirstName.clear();