（十一）Flutter表单验证与提交。Theme的定制使用重置，TextField文本字段。

修改main.dart

import &＃39;package:flutter/material.dart&＃39;;
import &＃39;package:nihao_flutter/demo/form_demo.dart&＃39;;
import &＃39;package:nihao_flutter/demo/navigator_demo.dart&＃39;;
import &＃39;package:nihao_flutter/demo/home_demo.dart&＃39;;void main() &＃61;> runApp(MyApp());class MyApp extends StatelessWidget {&＃64;overrideWidget build(BuildContext context) { // TODO: implement buildreturn MaterialApp(debugShowCheckedModeBanner: false,// home: NavigatorDemo(),initialRoute: &＃39;/form&＃39;,routes: {&＃39;/&＃39;:(context)&＃61;>HomeDemo(), &＃39;/form&＃39;:(context)&＃61;>FormDemo(), },theme: ThemeData(primarySwatch: Colors.yellow,highlightColor: Color.fromRGBO(255, 255, 255, 0.5),splashColor: Colors.red),);}
}

新建form_demo.dart

import &＃39;package:flutter/material.dart&＃39;;class FormDemo extends StatelessWidget {&＃64;overrideWidget build(BuildContext context) {return Scaffold(body: Theme(data: Theme.of(context).copyWith(primaryColor: Colors.black,),child: Container(padding: EdgeInsets.all(16.0),child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [RegisterForm(),],),),),);}
}class RegisterForm extends StatefulWidget {&＃64;overrideRegisterFormState createState() &＃61;> RegisterFormState();
}class RegisterFormState extends State {final registerFormKey &＃61; GlobalKey();String username, password;bool _autovalidate&＃61;false;void submintRegisterForm() {if(registerFormKey.currentState.validate()){registerFormKey.currentState.save();debugPrint(&＃39;username $username&＃39;);debugPrint(&＃39;password $password&＃39;);Scaffold.of(context).showSnackBar(SnackBar(content: Text(&＃39;Registering...&＃39;),));}else{setState(() {_autovalidate&＃61;true;});}}String validateUsername(value) {if (value.isEmpty) {return "Username os required.";}return null;}String validatePassword(value) {if (value.isEmpty) {return "Password is required.";}return null;}&＃64;overrideWidget build(BuildContext context) {return Form(key: registerFormKey,child: Column(children: [TextFormField(decoration: InputDecoration(labelText: &＃39;Username&＃39;,helperText: &＃39;please input Username&＃39;,),onSaved: (value) {username &＃61; value;},validator: validateUsername,autovalidate: _autovalidate,),TextFormField(obscureText: true,decoration: InputDecoration(labelText: &＃39;Password&＃39;,helperText: &＃39;please inputPassword&＃39;,),onSaved: (value) {password &＃61; value;},validator: validatePassword,autovalidate: _autovalidate,),SizedBox(height: 32.0,),Container(width: double.infinity,child: RaisedButton(color: Colors.green,child: Text(&＃39;Register&＃39;, style: TextStyle(color: Colors.white)),elevation: 0.0,onPressed: submintRegisterForm,),),],),);}
}class ThemeDemo extends StatelessWidget {&＃64;overrideWidget build(BuildContext context) {return Container(color: Theme.of(context).splashColor,);}
}class TextFieldDemo extends StatefulWidget {&＃64;overrideState createState() {// TODO: implement createStatereturn TextFieldDemoState();}
}class TextFieldDemoState extends State {final textEditingController &＃61; TextEditingController();&＃64;overridevoid dispose() {textEditingController.dispose();super.dispose();}&＃64;overridevoid initState() {super.initState();// textEditingController.text&＃61;&＃39;hi&＃39;;textEditingController.addListener(() {debugPrint(&＃39;input ${textEditingController.text}&＃39;);});}&＃64;overrideWidget build(BuildContext context) {// TODO: implement buildreturn TextField(controller: textEditingController,// onChanged: (value){// debugPrint(&＃39;input&＃xff1a;$value&＃39;);// },onSubmitted: (value) {debugPrint(&＃39;submit:$value&＃39;);},decoration: InputDecoration(icon: Icon(Icons.subject),labelText: &＃39;Title&＃39;,hintText: &＃39;Enter the post title.&＃39;,// border: InputBorder.none,// border: OutlineInputBorder(),filled: true,fillColor: Colors.green),);}
}

vscode f5运行看效果

android studio shift&＃43;f10