问题描述
我的 Flutter 小部件定义:
class LoginFormWidget extends StatefulWidget {
const LoginFormWidget({
Key key,@required this.loginFormKey,@required this.isEnabled,@required this.citiesListControl,@required this.onPasswordLoginpressed,@required this.onGuestLoginpressed,@required this.onGoogleLoginpressed,@required this.onFacebookLoginpressed,@required this.onEmailSaved,@required this.onPasswordSaved,this.statusText,}) : super(key: key);
//final GlobalKey<FormState> loginFormKey;
final Widget citiesListControl;
final bool isEnabled;
final String statusText;
final GlobalKey<FormState> loginFormKey;
final Function() onPasswordLoginpressed;
final Function() onGuestLoginpressed;
final Function() onGoogleLoginpressed;
final Function() onFacebookLoginpressed;
final Function(String) onEmailSaved;
final Function(String) onPasswordSaved;
@override
_LoginFormWidgetState createState() => _LoginFormWidgetState();
}
我定义了一些回调来处理登录按钮点击。对于登录电子邮件/密码,有一个登录按钮:
final loginButton = RaisedButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(24.0),),onpressed: widget.onPasswordLoginpressed,padding: EdgeInsets.all(12.0),color: Colors.lightBlueAccent,child: Text(Strings.btn_login,style: TextStyle(color: Colors.white),key: Key(Strings.btn_login)),);
要使用我的小部件:
LoginFormWidget(
isEnabled: _isCitySelected,onEmailSaved: (value) => _email = value,onPasswordSaved: (value) => _password = value,citiesListControl: citiesListControl,statusText: _status,loginFormKey: _loginFormKey,onPasswordLoginpressed: _isCitySelected
? () {
if (_loginFormKey.currentState.validate()) {
_loginFormKey.currentState.save();
_loginEmailPassword();
}
}
: null,
因此,如果没有选择城市(_isCitySelected
为 false) - 按钮的 onpressed 应为空(按钮已禁用)。否则,应执行验证和表单保存。
如何在我的情况下执行表单验证?如果我将表单密钥传递给我的小部件(密钥在我的根小部件中定义)并按上述方式执行验证和保存,我将收到异常:
I/Flutter (22322): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════
I/Flutter (22322): The following NoSuchMethodError was thrown while handling a gesture:
I/Flutter (22322): The method 'validate' was called on null.
I/Flutter (22322): Receiver: null
I/Flutter (22322): Tried calling: validate()
I/Flutter (22322):
I/Flutter (22322): When the exception was thrown,this was the stack:
I/Flutter (22322): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
I/Flutter (22322): #1 _LoginPageState._buildLoginForm.<anonymous closure> (package:lupe2/pages/login_page.dart:361:40)
I/Flutter (22322): #2 _InkResponseState._handleTap (package:Flutter/src/material/ink_well.dart:991:20)
I/Flutter (22322): #3 GestureRecognizer.invokeCallback (package:Flutter/src/gestures/recognizer.dart:182:24)
I/Flutter (22322): #4 TapGestureRecognizer.handleTapUp (package:Flutter/src/gestures/tap.dart:607:11)
I/Flutter (22322): #5 BaseTapGestureRecognizer._checkUp (package:Flutter/src/gestures/tap.dart:296:5)
onEmailSaved: (value) => _email = value,
是能够将表单值保存在我的小部件之外的回调函数。
解决方法
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