firebase - 我如何使用从其他页面获取的值

Question

我想使用从另一页获取并馈入构造函数的值。我已经尝试过，但是它给的错误为only static member can be accessed in initializers。任何人都可以让我知道如何使用从另一页获取的变量。或者，请让我知道是否有办法从Firebase获取详细信息，即用户电话号码并将其分配给globalNumber
这是我的代码。变量名称为globalNumber

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

var globalNumber;
bool valueExist;

class Pricepage extends StatefulWidget {
  @override
  _PricepageState createState() => _PricepageState();
}

class _PricepageState extends State<Pricepage> {

  var globalNumber;

  _PricepageState({this.globalNumber});
  StreamSubscription<DocumentSnapshot> subscription;
  final DocumentReference documentReference =
  Firestore.instance.document("users/$globalNumber"); // (Here this value comes from the previous page this is just the phonenumber of the user from firebase auth)

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    subscription = documentReference.snapshots().listen((datasnapshot) {
      if (datasnapshot.data.containsValue("true")) {
        setState(() {
          valueExist = true;
        });
      }
      else {
        setState(() {
          valueExist = false;
        });
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: getPrice(),


      ),
    );
  }

  Widget getPrice() {
    try {
      if (valueExist) {
        return Text('Prices are visibile');
      }

      else {
        return Text('Verify first');
      }
    }
    catch (e) {
      print(e);
    }
  }
}

Answer 1

答复2.0
主要问题在于以下行:

final DocumentReference documentReference =
  Firestore.instance.document("users/$globalNumber");

You should not initialize your final variable outside the initState(). You need to do it inside the initState() only. That is why you are getting this error. As in your error only says only static member can be accessed in initializers. And your static member is documentReference only, which has to be initialized inside the initializers, which is in our case is our initState()

这应该起作用

class _PricepageState extends State<Pricepage> {

  var globalNumber;

  _PricepageState({this.globalNumber});
  StreamSubscription<DocumentSnapshot> subscription;
  final DocumentReference documentReference;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    // initialise the value here
    documentReference = Firestore.instance.document("users/$globalNumber"); // (Here this value comes from the previous page this is just the phonenumber of the user from firebase auth)

    subscription = documentReference.snapshots().listen((datasnapshot) {
      if (datasnapshot.data.containsValue("true")) {
        setState(() {
          valueExist = true;
        });
      }
      else {
        setState(() {
          valueExist = false;
        });
      }
    });
  }
}

其余代码将保持不变。