如何在flutter中从firebase获取数据

Question

我正在构建一个 flutter 应用程序并使用 cloud-firestore，这就是我的数据库的样子

我想要一个函数，它在一个字符串数组中检索名为“驱动程序列表”的集合中的所有文档，这些文档是我已经使用过的，但它会将它们返回到新屏幕的列表视图中

class DriverList extends StatelessWidget {@overrideWidget build(BuildContext context) {
return new StreamBuilder<QuerySnapshot>(
  stream: Firestore.instance.collection('DriverList').snapshots(),
  builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
    if (!snapshot.hasData) return new Text('Loading...');
    return new ListView(
      children: snapshot.data.documents.map((DocumentSnapshot document) {
        return new ListTile(
          title: new Text(document['name']),
          subtitle: new Text(document['phone']),
        );
      }).toList(),
    );
  },
);

} }

Answer 1

这有一些额外的逻辑来删除潜在的重复记录，但您可以使用类似以下内容从 Firestore 检索数据。

我们访问集合引用，然后列出查询结果，然后为 Firestore 返回的数据创建本地模型对象，然后返回这些模型对象的列表。

  static Future<List<AustinFeedsMeEvent>> _getEventsFromFirestore() async {
CollectionReference ref = Firestore.instance.collection('events');
QuerySnapshot eventsQuery = await ref
    .where("time", isGreaterThan: new DateTime.now().millisecondsSinceEpoch)
    .where("food", isEqualTo: true)
    .getDocuments();

HashMap<String, AustinFeedsMeEvent> eventsHashMap = new HashMap<String, AustinFeedsMeEvent>();

eventsQuery.documents.forEach((document) {
  eventsHashMap.putIfAbsent(document['id'], () => new AustinFeedsMeEvent(
      name: document['name'],
      time: document['time'],
      description: document['description'],
      url: document['event_url'],
      photoUrl: _getEventPhotoUrl(document['group']),
      latLng: _getLatLng(document)));
});

return eventsHashMap.values.toList();
}

来源：https : //github.com/dazza5000/austin-feeds-me-flutter/blob/master/lib/data/events_repository.dart#L33

Answer 2

• 获取一次性数据：

  var collection = FirebaseFirestore.instance.collection('DriverList');
  var querySnapshot = await collection.get();
  for (var queryDocumentSnapshot in querySnapshot.docs) {
    Map<String, dynamic> data = queryDocumentSnapshot.data();
    var name = data['name'];
    var phone = data['phone'];
  }
  

• 每次更改时获取数据，使用StreamBuilder：

  StreamBuilder<QuerySnapshot<Map<String, dynamic>>>(
    stream: FirebaseFirestore.instance.collection('DriverList').snapshots(),
    builder: (_, snapshot) {
      if (snapshot.hasError) return Text('Error = ${snapshot.error}');
  
      if (snapshot.hasData) {
        final docs = snapshot.data!.docs;
        return ListView.builder(
          itemCount: docs.length,
          itemBuilder: (_, i) {
            final data = docs[i].data();
            return ListTile(
              title: Text(data['name']),
              subtitle: Text(data['phone']),
            );
          },
        );
      }
  
      return Center(child: CircularProgressIndicator());
    },
  )