Flutter 方法“resetPassword”在 null 上被調用

Question

我試圖創建一個按鈕，允許用戶重置他們的密碼。 但是，當我使用該方法時，它是在 null 上調用的。

我不知道我哪里做錯了。 我檢查了所有內容，它應該可以工作，因為我已經在名為 BaseAuth 的抽象類中實現了該方法。

有人可以幫我嗎？

這就是我如何使用 ResetPasswordPage

@override
Widget build(BuildContext context) {
_isIos = Theme.of(context).platform == TargetPlatform.iOS;
return new Scaffold(
    appBar: new AppBar(
      title: new Text("Organizer"),
      backgroundColor: Colors.blueAccent,
    ),
    body: Stack(
      children: <Widget>[
        _showBody(),
        _showCircularProgress(),
      ],
    ));
     }
Widget _showBody(){
return new Container(
    padding: EdgeInsets.all(10.0),
    child: new Form(
      key: _formKey,
      child: new ListView(
        shrinkWrap: true,
        children: <Widget>[
          _showEmailInput(),
          _showPasswordInput(),
          _showPrimaryButton(),
          _showSecondaryButton(),
          _resetPassword(),
        ],
      ),
    ));
     }
Widget _resetPassword() {
return new Padding(
  padding: EdgeInsets.fromLTRB(0.0, 0.0, 0.0, 0.0),
child : FlatButton(
  child: new Text('Forget password?',
      style:
      new TextStyle(fontSize: 18.0, fontWeight: FontWeight.w300)),
  onPressed: (){
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => ResetPasswordPage()),
    );
  }
)
);
}

這是 ResetPasswordPage 類

class ResetPasswordPage extends StatefulWidget {
ResetPasswordPage({Key key, this.auth});
final BaseAuth auth;
@override
_ResetPasswordPageState createState() => _ResetPasswordPageState();
}
class _ResetPasswordPageState extends State<ResetPasswordPage> {
String _email = '';
TextEditingController _emailController;
@override
void initState() {
super.initState();
final _emailController = TextEditingController(text: _email);
}

@override
void dispose() {
// Clean up the controller when the widget is disposed.
_emailController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
    appBar: new AppBar(
      title: new Text('Reset Password Page'),
      backgroundColor: Colors.red,
    ),
    body: Container(
      padding: EdgeInsets.all(10.0),
      child: ListView(
        children: <Widget>[
          new Padding(
            padding: const EdgeInsets.fromLTRB(0.0, 100.0, 0.0, 0.0),
            child: new TextField(
              maxLines: 1,
              keyboardType: TextInputType.emailAddress,
              decoration: new InputDecoration(
                  hintText: 'Email',
                  icon: new Icon(
                    Icons.mail,
                    color: Colors.grey,
                  )),
              onChanged: (value) {
                _email = value;
              },
              controller: _emailController,
            ),
          ),
          new Padding(
              padding: const EdgeInsets.fromLTRB(30.0, 20.0, 30.0, 0.0),
              child: RaisedButton(
                child: new Text('Sumbit',
                    style: new TextStyle(
                        fontSize: 18.0, fontWeight: FontWeight.w300)),
                onPressed: () async{
                  try{
                    await widget.auth.resetPassword('guanwenyan301@gmail.com');
                  }catch(e){
                    print(e);
                  }
                },
              ))
        ],
      ),
    ));
    }
     }

這是我的 BaseAuth 類：

abstract class BaseAuth {

Future<String> signIn(String email, String password);
Future<String> signUp(String email, String password);
Future<FirebaseUser> getCurrentUser();
Future<void> signOut();
Future<void> resetPassword(String email);}

class Auth implements BaseAuth {
final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
Future<String> signIn(String email, String password) async {
FirebaseUser user = await _firebaseAuth.signInWithEmailAndPassword(
    email: email, password: password);
if (user.isEmailVerified) {
  return user.uid;
}else{
  Fluttertoast.showToast(msg: 'Please verify your email');
}
}

Future<String> signUp(String email, String password) async {
FirebaseUser user = await _firebaseAuth.createUserWithEmailAndPassword(
    email: email, password: password);
await user.sendEmailVerification();
return user.uid;
}

Future<FirebaseUser> getCurrentUser() async {
FirebaseUser user = await _firebaseAuth.currentUser();
return user;
}

Future<void> signOut() async {
return _firebaseAuth.signOut();
}


Future<void> resetPassword(String email) async {
return _firebaseAuth.sendPasswordResetEmail(email: email);

}}

這是我得到的錯誤：

flutter: NoSuchMethodError: The method 'resetPassword' was called on 
null.
Receiver: null
Tried calling: resetPassword("guanwenyan301@gmail.com")

Answer 1

問題在這里

ResetPasswordPage({Key key, this.auth});
final BaseAuth auth;

當您從主小部件傳遞身份驗證時。 但在你的代碼中它不見了

Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => ResetPasswordPage()),
    );

所以需要創建**Auth**的實例，然后傳遞給路由中的ResetPasswordPage() 。

///像這樣初始化auth對象

auth = Auth();

/// 並像這樣在 onPressed 中傳遞它

onPressed: (){
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => ResetPasswordPage(auth : auth)), // first auth is the key in ResetPasswordPage and second auth is value 
    );
  }

Answer 2

您在未通過身份驗證的情況下創建了 ResetPasswordPage：

Navigator.push(
  context,
  MaterialPageRoute(builder: (context) => ResetPasswordPage()),
);

這意味着您的 ResetPasswordPage 下的身份驗證為空。 然后你用它來調用 resetPassword() 方法。 當然，你會得到例外。

解決方案：

...
onPressed: () {
  var auth = Auth();
  Navigator.push(
    context,
    MaterialPageRoute(builder: (context) => ResetPasswordPage(auth: auth)),
  );
}
...

希望能幫助到你！