如何制作像 Google 一样的 TextFormField？

Question

我对在 Flutter 上注册 Google 帐户时实现 TextField 感兴趣。如何从所有三个都有一个 errorText 的日期开始制作类似的一系列 TextField，当他们单击“下一步”时，一次检查三个，如果没有输入一个，即使它们是正确的，一切都会变成红色。这就像三者之一。

Answer 1

对于大纲文本字段，您可以使用

TextField(
  decoration: new InputDecoration(
      border: new OutlineInputBorder(),
      filled: true,
      hintText: "Type in your text",
   ),
)

对于验证，实现它的最佳方法是使用form with validation 和TextFormField 而不是TextField

示例：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appTitle = 'Form Validation Demo';

    return MaterialApp(
      title: appTitle,
      home: Scaffold(
        appBar: AppBar(
          title: Text(appTitle),
        ),
        body: MyCustomForm(),
      ),
    );
  }
}

// Create a Form widget.
class MyCustomForm extends StatefulWidget {
  @override
  MyCustomFormState createState() {
    return MyCustomFormState();
  }
}

// Create a corresponding State class.
// This class holds data related to the form.
class MyCustomFormState extends State<MyCustomForm> {
  // Create a global key that uniquely identifies the Form widget
  // and allows validation of the form.
  //
  // Note: This is a GlobalKey<FormState>,
  // not a GlobalKey<MyCustomFormState>.
  final _formKey = GlobalKey<FormState>();

  String _firstName;
  String _lastName;

  @override
  Widget build(BuildContext context) {
    // Build a Form widget using the _formKey created above.
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          TextFormField(
            validator: (value) {
              if (value.isEmpty) {
                return 'Please enter some text';
              }
              return null;
            },
            onSaved: (val) => _firstName = val,
          ),
          TextFormField(
            validator: (value) {
              if (value.isEmpty) {
                return 'Please enter some text';
              }
              return null;
            },
            onSaved: (val) => _lastName = val,
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: RaisedButton(
              onPressed: () {
                // Validate returns true if the form is valid, or false
                // otherwise.
                final form = _formKey.currentState;
                if (form.validate()) {
                  form.save();
                  // If the form is valid, display a Snackbar.
                  Scaffold.of(context).showSnackBar(SnackBar(
                      content: Text('The result: $_firstName, $_lastName')));
                }
              },
              child: Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}