在我的应用程序中，我希望从Firebase的不同集合中调用数据。首先，我想列出所有项目并取得ID。 我想使用该ID从价格收集中检索价格。之后，我想从折扣中检索数据。享受折扣。 在这里我正在使用循环。 在下面的代码中，输出即将到来。之后是第一个加载清单，它调用了第二个收集价格。 任何人都知道解决方案。 我想听三个人的电话。因为如果有任何数据更改，我想更新。
@override
void initState() {
super.initState();
_loadItems();
}
Future _loadItems() async {
int price;
int discount;
//calling first collection for getting id and name
firestore.collection("item").snapshots().listen((itemData)async{
for(int i=0;i<itemData.documents.length;i++){
// calling second collection for getting price
firestore.collection("price").where("id",isEqualTo: itemData.documents[i].data["id"])
.snapshots().listen((priceData) async{
price=priceData.documents[0].data['price'];
debugPrint("price showing before loading:"+price.toString());
//calling third collection for getting discount
firestore.collection("discount")
.where("id",isEqualTo: itemData.documents[i].data["id"])
.snapshots().listen((discountData) async{
for(int j=0;j<discountData.documents.length;j++){
discount=discountData.documents.data['discount'];
}
});
});
setState(() {
debugPrint("price showing after loading:"+price.toString());
this.documents.add(new CartProduct(
name:itemData.documents[i].data["id"],
label:itemData.documents[i].data["label"],
price:price,
discount:discount
));
});
}
});
}
price showing after loading:0
price showing after loading:0
price showing after loading:0
price showing before loading:10.0
price showing before loading:10.0
price showing before loading:10.0
price showing before loading:10.0
price showing before loading:10.0
price showing before loading:10.0
price showing after loading:10.0
price showing after loading:10.0
price showing after loading:10.0
答案 0 :(得分：2)
我可以使用嵌套的StreamBuilder
Widget getTripleCollectionFromFirebase() {
return StreamBuilder<QuerySnapshot>(
stream: Firestore.instance.collection("item").snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) return Text("Error: ${snapshot.error}");
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text("No data, yet.");
case ConnectionState.waiting:
return Text('Loading...');
case ConnectionState.active:
case ConnectionState.done:
if (snapshot.data == null) {
return Text("No record");
} else {
// Do your staff after first query then call the other collection
return StreamBuilder<QuerySnapshot>(
stream: Firestore.instance
.collection("price")
.where("id", isEqualTo: "fill_it_with_your_code")
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) return Text("Error: ${snapshot.error}");
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text("No data, yet.");
case ConnectionState.waiting:
return Text('Loading...');
case ConnectionState.active:
case ConnectionState.done:
if (snapshot.data == null) {
return Text("No record");
} else {
// do your staff after second Query
return StreamBuilder<QuerySnapshot>(
stream: Firestore.instance
.collection("discount")
.where("id", isEqualTo: "something")
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError)
return Text("Error: ${snapshot.error}");
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text("No data, yet.");
case ConnectionState.waiting:
return Text('Loading...');
case ConnectionState.active:
case ConnectionState.done:
if (snapshot.data == null) {
return Text("No record");
} else {
// do your staff after third Query
// return the widget which you want to build when all data comes.
}
}
},
);
}
}
},
);
}
}
},
);
}
答案 1 :(得分：0)
这是我的代码。我将逐步解释它，以便您可以将其转换为您的。
buildUserActions返回一个StreamBuilder，StreamBuilder会获取Cloud Firestore的动作集合中的所有文档。当ConnectionState为active或done（如果我有数据）时，将其分配给名为_lastActionDocuments的变量。
QuerySnapshot _lastActionDocuments;
Stream<String> streamOfFillActionFields;
Widget buildUserActions() {
return StreamBuilder(
initialData: _lastActionDocuments,
stream: Firestore.instance.collection('actions').snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
case ConnectionState.waiting:
return Center(
child: CircularProgressIndicator(),
);
case ConnectionState.active:
case ConnectionState.done:
if (snapshot.hasError)
return Center(child: Text('Error: ${snapshot.error}'));
if (!snapshot.hasData) return Text('No data finded!');
_lastActionDocuments = snapshot.data;
streamOfFillActionFields = fillActionFields();
return reallyBuildActions();
}
},
);
}
然后我有一个Stream函数
Stream<String> fillActionFields() async* {
try {
List<ActionModel> newActionList = [];
for (DocumentSnapshot actionSnapshot in _lastActionDocuments.documents) {
var currentAction = ActionModel.fromSnapshot(actionSnapshot);
// I awaiting to get and fill all data.
await currentAction.fillAllFields();
newActionList.add(currentAction);
}
actionList = newActionList;
// what I yield is not important this case
yield 'data';
} catch (e) {
print(e);
yield 'nodata';
}
}
currentAction.fillAllFields基本上，该功能要求Firebase获取相关数据以填充我的操作对象中的所有字段。
Future<void> fillAllFields() async {
DocumentSnapshot ownerSnapshot = await ownerRef.get();
owner = UserModel.fromSnapshot(ownerSnapshot);
DocumentSnapshot routeSnapshot = await routeRef.get();
route = RouteModel.fromSnapshot(routeSnapshot);
}
然后我有另一个小部件正在返回StreamBuilder。在所有数据均来自引用调用之后，此窗口小部件将构建真正的UI小部件（buildAllActions）。
Widget reallyBuildActions() {
return StreamBuilder(
stream: streamOfFillActionFields,
builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
case ConnectionState.waiting:
return Center(
child: CircularProgressIndicator(),
);
case ConnectionState.active:
case ConnectionState.done:
if (snapshot.data == 'data') {
return buildAllActions();
} else {
return Center(
child: Column(
children: <Widget>[
CircularProgressIndicator(),
Text('Data Loading...')
],
),
);
}
}
},
);
}
答案 2 :(得分：0)
我得到了答案使用StreamSubscription并一个一个地打电话。首先，我运行一个循环，然后仅在调用第二个循环之后检查它是否完成。它工作正常，但会延迟。当我使用StreamBuilder时，它没有完成请求。我不知道为什么会这样。我的代码如下所示。
StreamSubscription<QuerySnapshot> streamSub1;
StreamSubscription<QuerySnapshot> streamSub2;
StreamSubscription<QuerySnapshot> streamSub3;
var list = new List();
_loadItems() {
int price;
int discount;
int count =1;
//calling first collection for getting id and name
streamSub1= firestore.collection("item").snapshots().listen((itemData)async{
for(int i=0;i<itemData.documents.length;i++){
list.add(id:itemData.documents[0].data['id'],name:itemData.documents[0].data['id');
if(onFavData.documents.length==productCount){
debugPrint("loop completed");
_loadPrice();
}
}
});
}
void _loadPrice(){
streamSub1.cancel();
int count =1;
for(int i=0;i<list.length;i++){
streamSub2= firestore.collection("price").where("id",isEqualTo: itemData.documents[i].data["id"])
.snapshots().listen((priceData) async{
list[i].price= priceData['price'];
if(count==list.length){
debugPrint("loop completed");
_loadDiscount();
}
});
}
}
_loadDiscount();{
streamSub2.cancel();
int count =1;
for(int i=0;i<list.length;i++){
streamSub3= firestore.collection("price").where("id",isEqualTo: itemData.documents[i].data["id"])
.snapshots().listen((priceData) async{
list[i].discount= priceData['price'];
if(count==list.length){
debugPrint("loop completed");
}
});
}
}