firebase 在Firestore查询完成后，如何获得StreamBuilder结果？

1yjd4xko 于 2023-05-29 发布在其他

关注(0)|答案(2)|浏览(138)

我有一个从Firestore集合中检索数据的查询，该查询的值用于定义StreamBuilder要构建的流。
我发现StreamBuilder在Firestore查询完成之前构建流，这与查询完成然后StreamBuilder构建的结果不同。

@override
  Widget build(BuildContext context) {
    getData();
    final _dataSource = FirebaseFirestore.instance
        .collection(
        'users/l9NzQFjN4iB0JlJaY3AI/userA/2VzSHur3RllcF5PojT61/exclusiveA');
    return StreamBuilder<QuerySnapshot>(
        stream: _dataSource.where('preferredCurrency', isEqualTo: currency).snapshots().distinct(), // exclusiveA is being read
        // results should return only documents where preferredCurrency field = the value of currency field
        builder: (context, snapshot) {

有没有一种方法可以编写Flutter，以便在使用StreamBuilder构建UI之前完成Future类型的查询？

flutter: Login successful.
flutter: The vehicle's maximum speed = 233.0.
flutter: The vehicle's pulling strength = 2222.0 bhp.
flutter: The vehicle's brand is CCCCC, and its model-name is BBBBB.
flutter: The preferred currency = GBP.
flutter: The vehicle's maximum speed = 220.0.
flutter: The vehicle's pulling strength = 9000.0 bhp.
flutter: The vehicle's brand is PPPPP, and its model-name is LLLLL.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 235.0.
flutter: The vehicle's pulling strength = 440.0 bhp.
flutter: The vehicle's brand is KEXUZ, and its model-name is N2000.
flutter: The preferred currency = YEN.
flutter: The vehicle's maximum speed = 88.0.
flutter: The vehicle's pulling strength = 1100.0 bhp.
flutter: The vehicle's brand is Eord, and its model-name is Eiesta.
flutter: The preferred currency = GBP.
flutter: The vehicle's maximum speed = 110.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is Zadilax, and its model-name is Zrechlax.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 300.0.
flutter: The vehicle's pulling strength = 3200.0 bhp.
flutter: The vehicle's brand is XXXXX, and its model-name is XXXXXXXXXX.
flutter: The preferred currency = YEN.
flutter: The vehicle's maximum speed = 2000.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is MMMMM, and its model-name is MATHEMS.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 110.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is Zadilax, and its model-name is Azerlax.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 2000.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is AAAAAAAAA, and its model-name is BBBBBBBBB.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 280.0.
flutter: The vehicle's pulling strength = 2234.0 bhp.
flutter: The vehicle's brand is ABCDE12345, and its model-name is TEST MAY 24.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = null.
flutter: The vehicle's pulling strength = null bhp.
flutter: The vehicle's brand is , and its model-name is .
flutter: The preferred currency = .
flutter: The vehicle's maximum speed = 120.0.
flutter: The vehicle's pulling strength = 320.0 bhp.
flutter: The vehicle's brand is Snow Patrol, and its model-name is HD Rider 100.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 2000.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is AAAAAAAA, and its model-name is BBBBBBBB.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 220.0.
flutter: The vehicle's pulling strength = 3200.0 bhp.
flutter: The vehicle's brand is Neverlet, and its model-name is NL 5000.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 1234.0.
flutter: The vehicle's pulling strength = 1111.0 bhp.
flutter: The vehicle's brand is XXXXXZZZZZ, and its model-name is SASSCF.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 123456789.0.
flutter: The vehicle's pulling strength = 123456.0 bhp.
flutter: The vehicle's brand is MAY 22, and its model-name is Y2023.
flutter: The preferred currency = YEN.
flutter: The vehicle's maximum speed = 2000.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is XXXXX, and its model-name is ZZZZZ.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 250.
flutter: The vehicle's pulling strength = 500 bhp.
flutter: The vehicle's brand is CMW, and its model-name is K325S.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 80.0.
flutter: The vehicle's pulling strength = 1200.0 bhp.
flutter: The vehicle's brand is Niatt, and its model-name is POQ 123.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 225.0.
flutter: The vehicle's pulling strength = 12345.0 bhp.
flutter: The vehicle's brand is TTTTT, and its model-name is YYYYY.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = null.
flutter: The vehicle's pulling strength = null bhp.
flutter: The vehicle's brand is Percedes B, and its model-name is XLK.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 100.0.
flutter: The vehicle's pulling strength = 1000.0 bhp.
flutter: The vehicle's brand is WWWWW, and its model-name is WATCHEMS.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 200.
flutter: The vehicle's pulling strength = 500 bhp.
flutter: The vehicle's brand is Vercedes, and its model-name is QWE223.
flutter: The preferred currency = GBP.
flutter: The vehicle's maximum speed = 235.0.
flutter: The vehicle's pulling strength = 900.0 bhp.
flutter: The vehicle's brand is Percedes ZZ, and its model-name is ASLK.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 2222.0.
flutter: The vehicle's pulling strength = 1234.0 bhp.
flutter: The vehicle's brand is Vvvvvvvv, and its model-name is Aaaaaaaaa.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 500.0.
flutter: The vehicle's pulling strength = 500.5 bhp.
flutter: The vehicle's brand is J5 Ingram, and its model-name is B Way.
flutter: The preferred currency = USD.
flutter: The vehicle's maximum speed = 235.0.
flutter: The vehicle's pulling strength = 550.0 bhp.
flutter: The vehicle's brand is Vercedes ZXC, and its model-name is X46i.
flutter: The preferred currency = Euros.
flutter: The vehicle's maximum speed = 876543.0.
flutter: The vehicle's pulling strength = 1234.0 bhp.
flutter: The vehicle's brand is Ssssssss, and its model-name is Zzzzzzz.
flutter: The preferred currency = ZZZ.
flutter: The vehicle's maximum speed = 250.5.
flutter: The vehicle's pulling strength = 770.7 bhp.
flutter: The vehicle's brand is Vercedes ZXC, and its model-name is L55i.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 2800.0.
flutter: The vehicle's pulling strength = 1100.0 bhp.
flutter: The vehicle's brand is ZZZZZ, and its model-name is ZAPPEMS.
flutter: The preferred currency = EUR.
flutter: The current user's ID is: gaWoPCiLPWef9mCmd6WngDiS1I63 and their currency-choice = YEN.

上面的详细信息显示了在StreamBuilder开始构建之前Future类型查询未完成的结果：从Future查询到Flutter控制台的print语句是Flutter的最后输出，而流是整个集合的数据。
应该首先完成Future查询并确认'currency'值，然后过滤StreamBuilder结果，仅显示货币与查询中的'currency'值匹配的结果。

firebase

来源：https://stackoverflow.com/questions/76324053/how-can-i-get-streambuilder-results-after-a-firestore-query-has-been-completed

2条答案

按热度按时间

isr3a4wc1#

是的，在flutter中，您可以等待Future任务与FutureBuilder小部件竞争其执行。
这是你更新的代码

@override
Widget build(BuildContext context) {
  return FutureBuilder<QuerySnapshot>(
    future: getFutureData(),
    builder: (context, snapshot) {
      if (snapshot.connectionState == ConnectionState.waiting) {
        // Show a loading indicator while the query is being executed
        return CircularProgressIndicator();
      }

      if (snapshot.hasError) {
        // Handle any error that occurred during the query
        return Text('Error: ${snapshot.error}');
      }

      final _dataSource = snapshot.data.docs; // Access the documents from the query result

      return StreamBuilder<QuerySnapshot>(
        stream: _dataSource
            .where('preferredCurrency', isEqualTo: currency)
            .snapshots()
            .distinct(),
        builder: (context, snapshot) {
          // Build your UI based on the snapshot of the stream
          // ...
        },
      );
    },
  );
}

Future<QuerySnapshot> getFutureData() {
  final collectionRef = FirebaseFirestore.instance.collection(
      'users/l9NzQFjN4iB0JlJaY3AI/userA/2VzSHur3RllcF5PojT61/exclusiveA');
  return collectionRef.get();
}

赞(0）回复(0）举报 2023-05-29

ecbunoof2#

在发布了这个问题之后，我想到了一个解决我遇到的问题的方法。
我想，如果我可以从另一个类（例如最近发生导航的类）调用查询，那么StreamBuilder不会等待Future交付的数据可以及时提供给Stream Builder。我试过这种方法，效果很好。
我在这个解决方案中发现的另一件事是，我根本不需要Firestore查询，这是因为数据来自导航到StreamBuilder类的类。所以，我所要做的就是转移一些现有的数据。
我选择的技术是为StreamBuilder所在的类创建一个构造函数，然后在Navigator调用时添加相关数据。这样做确保了当StreamBuilder开始构建时，“货币”值可用，以便可以根据所选货币过滤StreamBuilder结果。

flutter: Login successful.
flutter: The vehicle's maximum speed = 220.0.
flutter: The vehicle's pulling strength = 9000.0 bhp.
flutter: The vehicle's brand is PPPPP, and its model-name is LLLLL.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 2000.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is AAAAAAAA, and its model-name is BBBBBBBB.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 2000.0.
flutter: The vehicle's pulling strength = 2000.0 bhp.
flutter: The vehicle's brand is XXXXX, and its model-name is ZZZZZ.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 80.0.
flutter: The vehicle's pulling strength = 1200.0 bhp.
flutter: The vehicle's brand is Niatt, and its model-name is POQ 123.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 225.0.
flutter: The vehicle's pulling strength = 12345.0 bhp.
flutter: The vehicle's brand is TTTTT, and its model-name is YYYYY.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = null.
flutter: The vehicle's pulling strength = null bhp.
flutter: The vehicle's brand is Percedes B, and its model-name is XLK.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 100.0.
flutter: The vehicle's pulling strength = 1000.0 bhp.
flutter: The vehicle's brand is WWWWW, and its model-name is WATCHEMS.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 235.0.
flutter: The vehicle's pulling strength = 900.0 bhp.
flutter: The vehicle's brand is Percedes ZZ, and its model-name is ASLK.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 230.0.
flutter: The vehicle's pulling strength = 2300.0 bhp.
flutter: The vehicle's brand is EEEEE, and its model-name is EEEEEEEEEE.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 2222.0.
flutter: The vehicle's pulling strength = 1234.0 bhp.
flutter: The vehicle's brand is Vvvvvvvv, and its model-name is Aaaaaaaaa.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 250.5.
flutter: The vehicle's pulling strength = 770.7 bhp.
flutter: The vehicle's brand is Vercedes ZXC, and its model-name is L55i.
flutter: The preferred currency = EUR.
flutter: The vehicle's maximum speed = 2800.0.
flutter: The vehicle's pulling strength = 1100.0 bhp.
flutter: The vehicle's brand is ZZZZZ, and its model-name is ZAPPEMS.
flutter: The preferred currency = EUR.

上面的细节显示了从另一个类传输StreamBuilder所需数据的结果。

class StreamResults extends StatelessWidget {

  final _auth = auth.FirebaseAuth.instance;
  final _dB = FirebaseFirestore.instance;
  final _dataSource = FirebaseFirestore.instance
      .collection(
      'users/l9NzQFjN4iB0JlJaY3AI/userA/2VzSHur3RllcF5PojT61/exclusiveA');

  String? vehicleMake, vehicleTitle, currentUserID, pCurrency, currency, uid, docRefID;
  num? maxSpeed, pullStrength;

  StreamResults({this.uid, this.currency, this.docRefID});

在上面的详细信息中，您可以看到StreamResults类的构造函数，它是解决方案的一部分。

Navigator.pushAndRemoveUntil(context, MaterialPageRoute(builder:(context) => StreamResults(uid: uid, currency: currency, docRefID: docRefID)), (route) => false);

上面的细节显示了解决方案的Navigator调用，用于同时更改屏幕和传输数据。

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firebase 在Firestore查询完成后，如何获得StreamBuilder结果？

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