flutter - 文本字段光标无法正常工作

Question

当我从数据库中检索数据并将其显示在文本字段中然后尝试对其进行编辑时，文本字段光标无法正常工作。

每次返回更改方法的验证结果时，我都希望光标的位置得到尊重。

完整代码如下。

import 'dart:async';

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'TextField Test',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  TextEditingController _nameController = TextEditingController();
  TextEditingController _emailController = TextEditingController();
  ApplicationBloc _bloc;

  @override
  void initState() {
    super.initState();
    _bloc = new ApplicationBloc();
    _bloc.initData();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('TextField Test'),
      ),
      body: ListView(
        shrinkWrap: true,
        children: <Widget>[_buildName(), _buildEmail(), _buildSubmit()],
      ),
    );
  }

  Widget _buildName() {
    return StreamBuilder(
      stream: _bloc.name,
      builder: (context, snapshot) {
        if (snapshot.hasData) {
          _nameController.text = snapshot.data;
        }
        return TextField(
          controller: _nameController,
          onChanged: _bloc.changeName,
          keyboardType: TextInputType.text,
          decoration: InputDecoration(
            labelText: "Name",
            errorText: snapshot.error,
          ),
        );
      },
    );
  }

  Widget _buildEmail() {
    return StreamBuilder(
      stream: _bloc.email,
      builder: (context, snapshot) {
        if (snapshot.hasData) {
          _emailController.text = snapshot.data;
        }
        return TextField(
          controller: _emailController,
          onChanged: _bloc.changeEmail,
          keyboardType: TextInputType.emailAddress,
          decoration: InputDecoration(
            labelText: "Email",
            errorText: snapshot.error,
          ),
        );
      },
    );
  }

  Widget _buildSubmit() {
    return StreamBuilder(
      stream: _bloc.submit,
      builder: (context, snapshot) {
        return RaisedButton(
          onPressed: (!snapshot.hasData || !snapshot.data)
              ? null
              : () {
                  _bloc.submitForm();
                  _nameController.text = '';
                  _emailController.text = '';
                },
          child: Text('Submit!'),
        );
      },
    );
  }
}

class ApplicationBloc {
  BehaviorSubject<String> _nameController =
      BehaviorSubject<String>(seedValue: '');
  Observable<String> get name => _nameController.stream.transform(validateName);
  Function(String) get changeName => _nameController.sink.add;

  BehaviorSubject<String> _emailController =
      BehaviorSubject<String>(seedValue: '');
  Observable<String> get email =>
      _emailController.stream.transform(validateEmail);
  Function(String) get changeEmail => _emailController.sink.add;

  Observable<bool> get submit => Observable.combineLatest2(
      name, email, (e, e1) => e.isNotEmpty && e1.isNotEmpty);

  initData() {
    // This data from database
    _nameController.sink.add('Test123');
    _emailController.sink.add('test@email.com');
  }    

  submitForm() {
    //Send to api and wait
    //Reset values
    Future.delayed(const Duration(seconds: 1));
  }

  final validateName =
      StreamTransformer<String, String>.fromHandlers(handleData: (name, sink) {
    if (name.isEmpty || name.length > 4) {
      sink.add(name);
    } else if (name.isNotEmpty) {
      sink.addError('Invalid Name!');
    }
  });

  final validateEmail =
      StreamTransformer<String, String>.fromHandlers(handleData: (email, sink) {
    String p =
        r'^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$';

    RegExp regExp = new RegExp(p);
    if (email.isEmpty || (email.length > 4 && regExp.hasMatch(email))) {
      sink.add(email);
    } else {
      sink.addError('Invalid email!');
    }
  });

  //dispose/close all the streams when we call dispose() method
  void dispose() {
    _nameController.close();
    _emailController.close();
  }
}

我尝试了一个将光标位置更改为最终位置的代码，但是当我尝试编辑文本字段的中间内容时它无法正常工作。

Answer 1

如果您查看 TextEditingController 的 text setter，您会看到:

set text(String newText) {
  value = value.copyWith(
    text: newText,
    selection: const TextSelection.collapsed(offset: -1),
    composing: TextRange.empty,
  );
}

请注意，selection 已重置，因此您无法使用此 setter 。相反，在您的构建器中，执行:

if (snapshot.hasData) {
  _nameController.value = _nameController.value.copyWith(
    text: snapshot.data,
  );
}

只是文本会发生变化，您不必担心其他属性。