Flutter 中引用 Firebase 的 DropdownButton 不会在选择后覆盖初始值

如何解决Flutter 中引用 Firebase 的 DropdownButton 不会在选择后覆盖初始值

我使用 TextFormFields 和 DropdownButtons 构建了一个 Flutter 表单来编辑用户配置文件。初始值是使用 FutureBuilder 从 Firebase 调用的。下拉列表中的列表也来自 Firebase。

问题1：在DropdownButtons中，选择后初始值不改变； Firebase 中的值保留在表单中。但是当您点击“保存”按钮时，它会使用选择正确更新 Firebase。如何覆盖初始值？我已经尝试了很多方法，但我认为这是国家问题。

问题 2： 如何向 DropdownButton 添加验证器以确保它不是空的？我无法让它工作。

非常感谢！

Screengrab

class EditProfilePage extends StatefulWidget {
  const EditProfilePage({Key key,@required this.database,this.profile})
      : super(key: key);
  final FirestoreDatabase database;
  final Profile profile;

  static Future<void> show(
    BuildContext context,{
    FirestoreDatabase database,Profile profile,}) async {
    await Navigator.of(context,rootNavigator: true).push(
      MaterialPageRoute(
        builder: (context) =>
            EditProfilePage(database: database,profile: profile),fullscreenDialog: true,),);
  }

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

class _EditProfilePageState extends State<EditProfilePage> {
  final _formKey = GlobalKey<FormState>();

  String userId;
  String name;
  String gender;
  String relationshipStatus;

  var _selectedGender;
  var _selectedRelationshipStatus;

  bool _validateAndSaveForm() {
    final form = _formKey.currentState;
    if (form.validate()) {
      form.save();
      return true;
    }
    return false;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        elevation: 2.0,title: Text('Edit Profile'),body: _buildContents(),backgroundColor: Colors.grey[200],);
  }

  Widget _buildContents() {
    return SingleChildScrollView(
      child: Padding(
        padding: const EdgeInsets.all(16.0),child: Card(
          child: Padding(
            padding: const EdgeInsets.all(16.0),child: _buildForm(),);
  }

  Widget _buildForm() {
    return Form(
      key: _formKey,child: _buildFormChildren(),);
  }

  Widget _buildFormChildren() {
    final auth = Provider.of<AuthBase>(context,listen: false);
    return FutureBuilder<DocumentSnapshot>(
      future: FirebaseFirestore.instance
          .collection('users')
          .doc(auth.currentUser.uid)
          .get(),builder:
          (BuildContext context,AsyncSnapshot<DocumentSnapshot> snapshot) {
        List<Widget> children;
        if (snapshot.hasData) {
          _selectedGender = snapshot.data['gender'];
          _selectedRelationshipStatus = snapshot.data['relationshipStatus'];
          children = <Widget>[
            TextFormField(
              decoration: Inputdecoration(labelText: 'Name'),initialValue: snapshot.data['name'],validator: (value) =>
                  value.isNotEmpty ? null : 'Name can\'t be empty',onSaved: (value) => name = value,FormField(
                initialValue: _selectedGender,builder: (FormFieldState state) {
                  return InputDecorator(
                    decoration: Inputdecoration(
                      labelText: 'Gender',child: StreamBuilder<QuerySnapshot>(
                        stream: FirebaseFirestore.instance
                            .collection('references')
                            .doc('profile_references')
                            .collection('gender')
                            .snapshots(),builder: (context,snapshot) {
                          if (!snapshot.hasData)
                            return const Center(
                              child: const CircularProgressIndicator(),);
                          var length = snapshot.data.docs.length;
                          DocumentSnapshot ds = snapshot.data.docs[length - 1];
                          return DropdownButton(
                            isDense: true,value: _selectedGender,hint: Text('Change to'),items: snapshot.data.docs
                                .map((DocumentSnapshot document) {
                              return DropdownMenuItem(
                                value: document.data()['gender'],child: Text(document.data()['gender']),);
                            }).toList(),onChanged: (value) {
                              setState(() {
                                gender = value;
                                _selectedGender = value;
                              });
                            },);
                        }),);
                }),FormField(
                initialValue: _selectedRelationshipStatus,builder: (FormFieldState state) {
                  return InputDecorator(
                    decoration: Inputdecoration(
                      labelText: 'Relationship Status',child: StreamBuilder<QuerySnapshot>(
                        stream: FirebaseFirestore.instance
                            .collection('references')
                            .doc('profile_references')
                            .collection('relationshipStatus')
                            .snapshots(),value: _selectedRelationshipStatus,items: snapshot.data.docs
                                .map((DocumentSnapshot document) {
                              return DropdownMenuItem(
                                value: document.data()['relationshipStatus'],child:
                                    Text(document.data()['relationshipStatus']),onChanged: (value) {
                              setState(() {
                                relationshipStatus = value;
                                _selectedRelationshipStatus = value;
                              });
                            },];
        } else if (snapshot.hasError) {
          children = <Widget>[
            Icon(
              Icons.error_outline,color: Colors.red,size: 60,Padding(
              padding: const EdgeInsets.only(top: 16),child: Text('Error: ${snapshot.error}'),)
          ];
        } else {
          children = <Widget>[
            SizedBox(
              child: CircularProgressIndicator(),width: 60,height: 60,const Padding(
              padding: EdgeInsets.only(top: 16),child: Text('Awaiting result...'),)
          ];
        }
        return Center(
          child: SingleChildScrollView(
            child: Column(
              children: [
                Column(
                  mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: children,SizedBox(height: 20),RaisedButton(
                  color: Colors.green[100],child: Text(
                    'Save',style: TextStyle(fontSize: 18,color: Colors.black),onpressed: () async {
                    if (_validateAndSaveForm()) {
                      try {
                        {
                          final profile = Profile(
                              name: name,gender: gender,relationshipStatus: relationshipStatus);
                          await widget.database.editProfile(profile);
                          Navigator.of(context).pop();
                        }
                      } on FirebaseException catch (e) {
                        showExceptionAlertDialog(
                          context,title: 'Operation Failed',exception: e,);
                      }
                    }
                  },],);
      },);
  }
}