I use firestore and streambuilder to read data in a list, when i run the application for the first time i get a message "Unexpected null value" and I realized that "snapshot.hasData" is always false and snapshot.ConnectionState.waiting is always true. But when i restart application with hot reload i can retrieve data.
This is my stream:
Stream<QuerySnapshot> _branchStream = FirebaseFirestore.instance.collection('Companies').doc(company_id).collection("Branch Offices").snapshots();
This is my StreamBuilder
StreamBuilder<QuerySnapshot>(
stream: _branchStream,
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
/* if (snapshot.hasError) {
return const Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return const Text("Loading");
}*/
return ListView(
children: snapshot.data!.docs
.map((DocumentSnapshot document) {
Map<String, dynamic> data =
document.data()! as Map<String, dynamic>;
return Padding(
padding: const EdgeInsets.all(22.0),
child: Card(
elevation: 8,
shadowColor: Colors.blueGrey,
shape: cardShape,
child: Row(
children: [
Expanded(
flex: 2,
child: Padding(
padding: const EdgeInsets.all(22.0),
child: CircleAvatar(
radius: 50,
backgroundImage:
NetworkImage(data['branch_image'],scale: 60),
),
)),
Expanded(
flex: 4,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Padding(
padding: const EdgeInsets.all(22.0),
child: Text(data['branch_name'], style: textBlackTitle, textAlign: TextAlign.center,),
),
Padding(
padding: const EdgeInsets.all(22.0),
child: Text("Ubicación: " data['branch_address'], style: textGraySubTitle, textAlign: TextAlign.center,),
),
],
)),
Expanded(
flex: 2,
child: IconButton(
// focusColor: Color(color1),
// color: Color(color1),
onPressed: (){
Navigator.push(context, MaterialPageRoute(builder: (context) => Home(branch_id : data['branch_id'], company_id : company_id, branch_name : data['branch_name'], branch_image : data['branch_image'])));
}, icon: Image.asset("assets/enter.png", fit: BoxFit.contain, height: 100,)))
],
),
),
);
})
.toList()
.cast(),
);
},
)
This is data that I want to get
This is what I get at the first time
This is what I get after hot reload (That I should have from the beginning).
CodePudding user response：
Because your data is null at the beginning, it takes some time to load the data.
You actually already included a check, but commented it out again. Undo it and try again.
/* if (snapshot.hasError) {
return const Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return const Text("Loading");
}*/
CodePudding user response：
It takes some time to load snapshot data. For better UX return specific widgets for each state of the snapshot.
Make sure you're using StreamBuilder inside StatefulWidget.
StreamBuilder<QuerySnapshot>(
stream: _branchStream,
builder: (BuildContext context, snapshot) {
if (snapshot.hasError) {
return //error widget
} else {
switch (snapshot.connectionState) {
case ConnectionState.none:
return //some widget
case ConnectionState.waiting:
return CircularProgressIndicator(),
case ConnectionState.active:
return ListView()
case ConnectionState.done:
return //some widget
}
}
);