我試圖TextFormFields在我的專案中驗證兩個（電子郵件和密碼）。但是我在驗證TextFormField. 有人可以讓我知道我哪里出錯了嗎？或者如何修復錯誤。
我得到的錯誤是： ════════ Exception caught by gesture ═══════════════════════════════════════════ Null check operator used on a null value ════════════════════════════════════════════════════════════════════════════════
我的代碼：
class _LoginState extends State<Login> {
@override
Widget build(BuildContext context) {
final _formKey = GlobalKey<FormState>();
TextEditingController emailController;
TextEditingController passwordController;
final authService = Provider.of<AuthService>(context);
emailController = TextEditingController();
passwordController = TextEditingController();
return Scaffold(
backgroundColor: Colors.white,
body: SingleChildScrollView(
child: Column(children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 60.0),
child: Center(
child: Container(
width: 300,
height: 380,
decoration:
BoxDecoration(borderRadius: BorderRadius.circular(50.0)),
child: Image.asset(
'assets/images/logo.png',
)),
),
),
const SizedBox(height: 15.0),
Padding(
padding: EdgeInsets.only(left: 25.0, right: 25.0, top: 0, bottom: 0),
child: TextFormField(
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter the email.';
}
return null;
},
controller: emailController,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(60),
),
prefixIcon: const Icon(Icons.mail),
labelText: 'E-Mail',
hintText: '[email protected]'),
),
),
Padding(
padding: EdgeInsets.only(left: 25.0, right: 25.0, top: 15, bottom: 0),
child: TextFormField(
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter the password.';
}
return null;
},
controller: passwordController,
obscureText: true,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(60),
),
prefixIcon: const Icon(Icons.vpn_key),
labelText: 'Password',
hintText: 'Enter your Password'),
),
),
const SizedBox(
height: 100,
),
TextButton(
onPressed: () {
if (_formKey.currentState!.validate()) {
ScaffoldMessenger.of(context).showSnackBar(
const SnackBar(content: Text('Processing')),
);
}
authService.signInWithEmailAndPassword(context,
emailController.text.trim(), passwordController.text.trim());
},
child: const Text(
'Login',
textAlign: TextAlign.center,
)),
MaterialButton(
onPressed: () {
Navigator.push(context,
MaterialPageRoute(builder: (context) => forgotPassword()));
},
child: Text(
'Forgot Password',
textAlign: TextAlign.center,
style: TextStyle(fontSize: 13.0, color: Colors.red.shade900),
))
])),
);
}
}
先感謝您。
uj5u.com熱心網友回復：
您的代碼段中沒有Form使用小部件_formKey，這就是它從_formKey.currentState!.validate(). 因為你正在使用!那個說currentState of formKey永遠不會為空的。
您可以通過首先檢查空狀態來處理它。
TextButton(
onPressed: () {
if (_formKey.currentState == null) {
return; // dont execute rest code
}
if (_formKey.currentState!.validate()) {
ScaffoldMessenger.of(context).showSnackBar(
const SnackBar(content: Text('Processing')),
);
authService.signInWithEmailAndPassword(context,
emailController.text.trim(),
passwordController.text.trim());
},
將Form小Column部件放在小部件之前。
body: SingleChildScrollView(
child: Form(
key: _formKey,
child: Column(children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 60.0),
child: Center(
有關表單驗證的更多資訊
uj5u.com熱心網友回復：
您導致此錯誤是因為您在代碼中定義了_formkey但未定義used它，因此它沒有任何value或State現在您必須將TextFormField包裝在Form小部件中并需要傳遞定義的鍵，您可以檢查下面的代碼
final _formKey = GlobalKey<FormState>();
class _LoginState extends State<Login> {
@override
Widget build(BuildContext context) {
TextEditingController emailController;
TextEditingController passwordController;
final authService = Provider.of<AuthService>(context);
emailController = TextEditingController();
passwordController = TextEditingController();
return Scaffold(
backgroundColor: Colors.white,
body: SingleChildScrollView(
child: Column(children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 60.0),
child: Center(
child: Container(
width: 300,
height: 380,
decoration:
BoxDecoration(borderRadius: BorderRadius.circular(50.0)),
child: Image.asset(
'assets/images/logo.png',
)),
),
),
const SizedBox(height: 15.0),
Form(
key: _formKey,
child: Padding(
padding: EdgeInsets.only(left: 25.0, right: 25.0, top: 0, bottom: 0),
child: TextFormField(
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter the email.';
}
return null;
},
controller: emailController,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(60),
),
prefixIcon: const Icon(Icons.mail),
labelText: 'E-Mail',
hintText: '[email protected]'),
),
),
),
Padding(
padding: EdgeInsets.only(left: 25.0, right: 25.0, top: 15, bottom: 0),
child: TextFormField(
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter the password.';
}
return null;
},
controller: passwordController,
obscureText: true,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(60),
),
prefixIcon: const Icon(Icons.vpn_key),
labelText: 'Password',
hintText: 'Enter your Password'),
),
),
const SizedBox(
height: 100,
),
TextButton(
onPressed: () {
if (_formKey.currentState!.validate()) {
ScaffoldMessenger.of(context).showSnackBar(
const SnackBar(content: Text('Processing')),
);
}
authService.signInWithEmailAndPassword(context,
emailController.text.trim(), passwordController.text.trim());
},
child: const Text(
'Login',
textAlign: TextAlign.center,
)),
MaterialButton(
onPressed: () {
Navigator.push(context,
MaterialPageRoute(builder: (context) => forgotPassword()));
},
child: Text(
'Forgot Password',
textAlign: TextAlign.center,
style: TextStyle(fontSize: 13.0, color: Colors.red.shade900),
))
])),
);
}
}
轉載請註明出處，本文鏈接：https://www.uj5u.com/ruanti/388066.html