在颤动中禁用图标按钮

Question

我想根据 'flag' 变量中存储的值禁用图标按钮。

这是我的代码：

class PlaceTile extends StatelessWidget {
  

  final Place place;
  PlaceTile({ this.place });

  getUserById(String id) {
    
    DatabaseService().placesCollection.document(id).get().then((DocumentSnapshot doc) {
      print(doc.data);
  
    });

  }

  checkUserStatus() async {
    
     String flag='inactive';

    final FirebaseAuth auth = FirebaseAuth.instance;
    
    final FirebaseUser user  = await auth.currentUser();
    String uid = user.uid;
    UserDatabaseService().userCollection.getDocuments().then((QuerySnapshot snapshot) {
      snapshot.documents.forEach((DocumentSnapshot doc) {
        if(doc.documentID == uid)
        {
          if(doc.data['status']=='true')
          {
              flag = 'active';
          }
        }
        });
    });
    return flag;
  }


  String value;

  @override
  Widget build(BuildContext context) {
    void showQueueDetailsPanel() {
      showModalBottomSheet(context: context, builder: (context) {
        return Container(
          padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 60.0),
          child: QueueDetails(value: place.name),
        );
      });
    }
    return Padding(
      padding: EdgeInsets.only(top: 8.0),
      child: Card(
        margin: EdgeInsets.fromLTRB(20.0, 6.0, 20.0, 0.0),
        child: ListTile(
          isThreeLine: true,
          leading: CircleAvatar(
            radius: 25.0,
            backgroundColor: Colors.white,
          ),
            title: Text(place.name),
            subtitle: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                //Text("People   "+place.totalPeople.toString()),
                Text(""),
                Text("Token    "+place.tokenAvailable.toString()),
              ],
            ),
            
            trailing: FlatButton.icon(
              icon: Icon(Icons.add_box_rounded),
              label: Text('Join'),
              onPressed: checkUserStatus()=='inactive' ?
              () async => showQueueDetailsPanel() : null,
            ),
          ),
        )
    );
    }
}

但是，即使onPressed 条件为“非活动”，所有“加入”按钮都被禁用。我尝试通过单独运行这两个函数来调试代码，看起来还不错。但是，每当我使用onPressed 条件来检查flag 变量时，所有按钮似乎都被禁用了，即使条件显然是正确的。

编辑 1

class PlaceTile extends StatelessWidget {
  

  final Place place;
  PlaceTile({ this.place });

  getUserById(String id) {
    
    DatabaseService().placesCollection.document(id).get().then((DocumentSnapshot doc) {
      print(doc.data);
  
    });

  }

  String checkUserStatus()  {
    
     String flag='inactive';

    final FirebaseAuth auth = FirebaseAuth.instance;
    
    //final FirebaseUser user  = await auth.currentUser();
    auth.currentUser().then((user) {
    String uid = user.uid;
    UserDatabaseService().userCollection.getDocuments().then((QuerySnapshot snapshot) {
      snapshot.documents.forEach((DocumentSnapshot doc) {
        if(doc.documentID == uid)
        {
          if(doc.data['status']=='true')
          {
              flag = 'active';
          }
        }
        });
    });

  });
      return flag;
  }


  String value;

  @override
  Widget build(BuildContext context) {
    void showQueueDetailsPanel() {
      showModalBottomSheet(context: context, builder: (context) {
        return Container(
          padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 60.0),
          child: QueueDetails(value: place.name),
        );
      });
    }
    return Padding(
      padding: EdgeInsets.only(top: 8.0),
      child: Card(
        margin: EdgeInsets.fromLTRB(20.0, 6.0, 20.0, 0.0),
        child: ListTile(
          isThreeLine: true,
          leading: CircleAvatar(
            radius: 25.0,
            backgroundColor: Colors.white,
          ),
            title: Text(place.name),
            subtitle: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                //Text("People   "+place.totalPeople.toString()),
                Text(""),
                Text("Token    "+place.tokenAvailable.toString()),
              ],
            ),
            
            trailing: FlatButton.icon(
              icon: Icon(Icons.add_box_rounded),
              label: Text('Join'),
              onPressed: checkUserStatus()=='inactive' ?
              () async => showQueueDetailsPanel() : null,
            ),
          ),
        )
    );
    }
}

Answer 1

您正在尝试使 Stateless 小部件具有状态。要使您的代码正常工作，您需要将 Stateless 小部件转换为 Statefull 小部件。

您的代码如下所示：

class PlaceTile extends StatefulWidget {
  final Place place;
  PlaceTile({this.place});

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

class _PlaceTileState extends State<PlaceTile> {
  String flag = 'inactive';

  @override
  initState() {
    super.initState();
    checkUserStatus();
  }

  void getUserById(String id) {
    DatabaseService()
        .placesCollection
        .document(id)
        .get()
        .then((DocumentSnapshot doc) {
      print(doc.data);
    });
  }

  Future checkUserStatus() async {
    final FirebaseAuth auth = FirebaseAuth.instance;

    final FirebaseUser user = await auth.currentUser();
    String uid = user.uid;
    UserDatabaseService()
        .userCollection
        .getDocuments()
        .then((QuerySnapshot snapshot) {
      snapshot.documents.forEach((DocumentSnapshot doc) {
        if (doc.documentID == uid) {
          if (doc.data['status'] == 'true') {
            setState(() {
              flag = 'active';
            });
          }
        }
      });
    });
    return flag;
  }

      void showQueueDetailsPanel() {
    showModalBottomSheet(
        context: context,
        builder: (context) {
          return Container(
            padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 60.0),
            child: QueueDetails(value: widget.place.name),
          );
        });
  }


  @override
  Widget build(BuildContext context) {


    return Padding(
        padding: EdgeInsets.only(top: 8.0),
        child: Card(
          margin: EdgeInsets.fromLTRB(20.0, 6.0, 20.0, 0.0),
          child: ListTile(
            isThreeLine: true,
            leading: CircleAvatar(
              radius: 25.0,
              backgroundColor: Colors.white,
            ),
            title: Text(widget.place.name),
            subtitle: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                //Text("People   "+place.totalPeople.toString()),
                Text(""),
                Text("Token    " + widget.place.tokenAvailable.toString()),
              ],
            ),
            trailing: FlatButton.icon(
              icon: Icon(Icons.add_box_rounded),
              label: Text('Join'),
              onPressed: flag == 'inactive' ? showQueueDetailsPanel : null,
            ),
          ),
        ));
  }
}

Answer 2

  String checkUserStatus() {
    String flag = 'inactive';

    final FirebaseAuth auth = FirebaseAuth.instance;

    auth.currentUser().then((user) {
      String uid = user.uid;
      UserDatabaseService()
          .userCollection
          .getDocuments()
          .then((QuerySnapshot snapshot) {
        snapshot.documents.forEach((DocumentSnapshot doc) {
          if (doc.documentID == uid) {
            if (doc.data['status'] == 'true') {
              flag = 'active';
            }
          }
        });
      });
      return flag;
    });
  }

onPressed: checkUserStatus() == 'inactive'
                  ? () async => showQueueDetailsPanel()
                  : null,

如果 checkUserStatus() 用作异步函数，则应等待它或通过 .then() 访问其值。