底部导航栏在登录时消失，但是在我转到另一个页面并返回时又返回？

分类：编程问答

如何解决底部导航栏在登录时消失，但是在我转到另一个页面并返回时又返回？

我正在尝试创建一个应用，该应用将向用户显示带有产品的通用首页，并为他们提供导航到帐户页面的选项，如果未登录，则将在其中显示登录/注册页面或如果他们已登录，则将向他们显示其个人资料。

我设法使登录/退出部分正常工作，但是当我登录并导航到个人资料页面时，我的底部导航栏消失了。但是，当我导航到另一个页面并返回时，它会重新出现。

这是我的home.dart文件，用于控制我的应用的导航：

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  PageController _pageController = PageController();
  List<Widget> _screens = [HomePage(),InboxPage(),AccountController()];


  int _selectedIndex = 0;

  void _onPageChanged(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }

  void _onItemTapped(int selectedIndex) {
    _pageController.jumpToPage(selectedIndex);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: PageView(
        controller: _pageController,children: _screens,onPageChanged: _onPageChanged,physics: NeverScrollableScrollPhysics(),),bottomNavigationBar: BottomNavigationBar(onTap: _onItemTapped,items: [
        BottomNavigationBarItem(
          icon: Icon(
            Icons.home,color: _selectedIndex == 0 ? Colors.blueAccent : Colors.grey,title: Text(
            'Home',style: TextStyle(
              color: _selectedIndex == 0 ? Colors.blueAccent : Colors.grey,BottomNavigationBarItem(
          icon: Icon(
            Icons.email,color: _selectedIndex == 1 ? Colors.blueAccent : Colors.grey,title: Text(
            'Inbox',style: TextStyle(
              color: _selectedIndex == 1 ? Colors.blueAccent : Colors.grey,BottomNavigationBarItem(
          icon: Icon(
            Icons.account_circle,color: _selectedIndex == 2 ? Colors.blueAccent : Colors.grey,title: Text(
            'Account',style: TextStyle(
              color: _selectedIndex == 2 ? Colors.blueAccent : Colors.grey,]),);
  }
}

我的accountcontroller.dart代码可帮助确定用户是否已登录：

class AccountController extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final AuthService auth = Provider.of(context).auth;
    return StreamBuilder(
        stream: auth.onAuthStateChanged,builder: (context,AsyncSnapshot<String> snapshot) {
          if (snapshot.connectionState == ConnectionState.active) {
            final bool signedIn = snapshot.hasData;
            return signedIn ? ProfileView() : SignUpPage();
          }
          return CircularProgressIndicator();
        });
  }
}

我的个人资料view.dart：

class ProfileView extends StatefulWidget {

  @override
  _ProfileViewState createState() => _ProfileViewState();
}

class _ProfileViewState extends State<ProfileView> {


  @override
  Widget build(BuildContext context) {
    return
      Scaffold(
        appBar: PreferredSize(
            preferredSize: const Size.fromHeight(80),child: MainAppBar(
              text: 'Account',)),body: SingleChildScrollView(
        child: Column(
        children: <Widget>[
          Text('Account Page'),showSignOut(context),goToHomepage(context),],);
  }
}

Widget showSignOut(context) {
  return RaisedButton(
      child: Text('Sign Out'),onPressed: () async {
        try {
          await Provider.of(context).auth.signOut();
          Navigator.pushNamed(context,'/homepage');
          print('Signed Out');
        } catch (e) {
          print(e);
        }
      });
}

Widget goToHomepage(context) {
  return RaisedButton(
      child: Text('Go to homepage'),onPressed: () async {
        try {
          Navigator.pushNamed(context,'/homepage');
        } catch (e) {
          print(e);
        }
      });
}

最后是我的signup.dart文件，其中包含我的注册/登录代码：

enum AuthFormType { signIn,signUp }

class SignUpPage extends StatefulWidget {
  final AuthFormType authFormType;

  SignUpPage({Key key,this.authFormType}) : super(key: key);

  @override
  _SignUpPageState createState() =>
      _SignUpPageState(authFormType: this.authFormType);
}

class _SignUpPageState extends State<SignUpPage> {
  AuthFormType authFormType;

  _SignUpPageState({this.authFormType});

  final formKey = GlobalKey<FormState>();
  String _firstName,_lastName,_email,_confirmEmail,_password,_confirmPassword,_dateOfBirth;

  bool validate() {
    final form = formKey.currentState;
    form.save();
    if (form.validate()) {
      form.save();
      print('true');
      return true;
    } else {
      print('false');
      return false;
    }
  }

  void switchFormState(String state) {
    formKey.currentState.reset();
    if (state == 'signIn') {
      setState(() {
        authFormType = AuthFormType.signIn;
      });
    } else {
      setState(() {
        authFormType = AuthFormType.signUp;
      });
    }
  }

  void submit() async {
    final CollectionReference userCollection =
        Firestore.instance.collection('UserData');

    if (validate()) {
      try {
        final auth = Provider.of(context).auth;
        if (authFormType == AuthFormType.signIn) {
          String uid = await auth.signInWithEmailAndPassword(_email,_password);
          print("Signed In with ID $uid");
          Navigator.of(context).pushReplacementNamed('/home');
        } else {
          String uid = await auth.createUserWithEmailAndPassword(
            _email,);
          userCollection.document(uid).setData({
            'First Name': _firstName,'Last Name': _lastName,'Date of Birth': _dateOfBirth
          });
          print("Signed up with New ID $uid");
          Navigator.of(context).pushReplacementNamed('/home');
        }
      } catch (e) {
        print(e);
      }
    }
  }

  DateTime selectedDate = DateTime.now();
  TextEditingController _date = new TextEditingController();

  Future<Null> _selectDate(BuildContext context) async {
    DateFormat formatter =
        DateFormat('dd/MM/yyyy'); //specifies day/month/year format

    final DateTime picked = await showDatePicker(


        context: context,initialDate: selectedDate,firstDate: DateTime(1901,1),builder: (BuildContext context,Widget child) {
          return Theme(
            data: ThemeData.light().copyWith(
              colorScheme: ColorScheme.light(
                primary: kPrimaryColor,onPrimary: Colors.black,buttonTheme: ButtonThemeData(
                colorScheme: Theme.of(context)
                    .colorScheme
                    .copyWith(primary: Colors.black),child: child,);
        },lastDate: DateTime(2100));

    if (picked != null && picked != selectedDate)
      setState(() {
        selectedDate = picked;
        _date.value = TextEditingValue(
            text: formatter.format(
                picked)); //Use formatter to format selected date and assign to text field
      });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: PreferredSize(
            preferredSize: const Size.fromHeight(80),child: MainAppBar(
              text: buildAppBarText(),body: SingleChildScrollView(
          child: Padding(
            padding: const EdgeInsets.all(12.0),child: Center(
              child: Container(
                child: Column(
                  children: <Widget>[
                    Align(
                      child: Text(buildTitleText(),style: AppBarTextStyle),Container(
                      padding: EdgeInsets.only(top: 10),Padding(
                      padding: const EdgeInsets.all(20.0),child: Form(
                          key: formKey,child: Column(
                            children: buildInputs() + buildSwitchText(),));
  }

  buildHeaderText() {
    String _headerText;
    if (authFormType == AuthFormType.signUp) {
      _headerText = "Don't have an account?";
    } else {
      _headerText = "Already have an account?";
    }
    return _headerText;
  }

  List<Widget> buildInputs() {
    List<Widget> textFields = [];

    DateFormat dateFormat = DateFormat("yyyy-MM-dd HH:mm:ss");

    if (authFormType == AuthFormType.signIn) {
      textFields.add(TextFormField(
          style: TextStyle(
            fontSize: 12.0,decoration: buildSignUpInputDecoration('Email'),validator: SignInEmailValidator.validate,onSaved: (value) => _email = value.trim()));
      textFields.add(SizedBox(
        height: 15,));
      textFields.add(
        TextFormField(
          style: TextStyle(
            fontSize: 12.0,decoration: buildSignUpInputDecoration('Password'),obscureText: true,validator: SignInPasswordValidator.validate,onSaved: (value) => _password = value.trim(),);
    } else {
      textFields.clear();
      //if we're in the sign up state,add name
      // add email & password
      textFields.add(TextFormField(
        style: TextStyle(
          fontSize: 12.0,decoration: buildSignUpInputDecoration('First Name'),validator: NameValidator.validate,onSaved: (value) => _firstName = value,));
      textFields.add(SizedBox(
        height: 15,));
      textFields.add(TextFormField(
        style: TextStyle(
          fontSize: 12.0,decoration: buildSignUpInputDecoration('Last Name'),onSaved: (value) => _lastName = value,decoration: buildSignUpInputDecoration('Email Address'),onSaved: (value) => _email = value.trim(),decoration: buildSignUpInputDecoration('Confirm Email Address'),onSaved: (value) => _confirmEmail = value,validator: (confirmation) {
          return confirmation == _email
              ? null
              : "Confirm Email Address should match email address";
        },onSaved: (value) => _password = value,));
      textFields.add(TextFormField(
          style: TextStyle(
            fontSize: 12.0,decoration: buildSignUpInputDecoration('Confirm Password'),onSaved: (value) => _confirmPassword = value,validator: (confirmation) {
            return confirmation == _password
                ? null
                : "Confirm Password should match password";
          }));
      textFields.add(SizedBox(
        height: 15,));
      textFields.add(GestureDetector(
        onTap: () => _selectDate(context),child: AbsorbPointer(
          child: TextFormField(
            style: TextStyle(fontSize: 12.0),controller: _date,keyboardType: TextInputType.datetime,decoration: InputDecoration(
              isDense: true,fillColor: Colors.white,hintText: 'Date of Birth',filled: true,enabledBorder: OutlineInputBorder(
                borderSide: BorderSide(width: 0.0),contentPadding:
                  const EdgeInsets.only(left: 14.0,bottom: 10.0,top: 10.0),onSaved: (value) => _dateOfBirth = value,));

      textFields.add(SizedBox(
        height: 15,));
    }
    return textFields;
  }

  List<Widget> buildSwitchText() {
    String _switchButtonTextPart1,_switchButtonTextPart2,_newFormState;

    if (authFormType == AuthFormType.signIn) {
      _switchButtonTextPart1 = "Haven't got an account? ";
      _switchButtonTextPart2 = 'Sign Up';
      _newFormState = 'signUp';
    } else {
      _switchButtonTextPart1 = 'Already have an account? ';
      _switchButtonTextPart2 = 'Sign In';
      _newFormState = 'signIn';
    }
    return [
      SizedBox(height: 5.0),Container(
        width: MediaQuery.of(context).size.height * 0.7,child: RaisedButton(
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(5.0),color: kPrimaryColor,textColor: Colors.black,child: Padding(
              padding: const EdgeInsets.all(8.0),child: Text(
                buildTitleText(),style: TextStyle(fontFamily: FontNameDefault,fontSize: 15.0),onPressed: submit),SizedBox(
        height: 5.0,RichText(
        text: TextSpan(
            style: TextStyle(
              fontFamily: FontNameDefault,color: Colors.black,fontSize: 12.0,children: <TextSpan>[
              TextSpan(text: _switchButtonTextPart1),TextSpan(
                  text: _switchButtonTextPart2,style: TextStyle(
                      decoration: TextDecoration.underline,fontSize: 12.0),recognizer: TapGestureRecognizer()
                    ..onTap = () {
                      switchFormState(_newFormState);
                    })
            ]),];
  }

  String buildAppBarText() {
    String _switchAppBarHeader;

    if (authFormType == AuthFormType.signIn) {
      _switchAppBarHeader = "Already have an account?";
    } else {
      _switchAppBarHeader = "Don't have an account?";
    }
    return _switchAppBarHeader;
  }

  String buildTitleText() {
    String _switchTextHeader;

    if (authFormType == AuthFormType.signIn) {
      _switchTextHeader = "Sign In";
    } else {
      _switchTextHeader = "Sign Up";
    }
    return _switchTextHeader;
  }
}


InputDecoration buildSignUpInputDecoration(String hint) {
  return InputDecoration(
    isDense: true,hintText: hint,enabledBorder: OutlineInputBorder(
      borderSide: BorderSide(width: 0.0),contentPadding: const EdgeInsets.only(left: 14.0,);
}

有什么想法吗？

解决方法

HomePage（），InboxPage（）和AccountController（）位于您的家庭小部件中，其中包含bottomNavigationBar。 您的个人资料页面和注册页面是具有自己的支架的不同页面。 您必须创建一个中央“索引”窗口小部件，其中包含每个子页面和导航栏。

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