admob bannerads do not show in dynamic list - firebase

Question

I am trying to display a bannerAd between every 3 posts. But ads do not show. I presume, that the list could be empty, as this list is a list build from the posts user likes and saves.
#override
Widget build(BuildContext context) {
return Expanded(
child: ListView(
padding: EdgeInsets.symmetric(horizontal: 10.0),
children: [
StreamBuilderWrapper(
shrinkWrap: true,
stream: postRef
.where("bookmarks",
arrayContains: FirebaseAuth.instance.currentUser.uid)
.orderBy('timestamp', descending: true)
.snapshots(),
physics: NeverScrollableScrollPhysics(),
itemBuilder: (_, DocumentSnapshot snapshot) {
internetChecker(context);
Review posts = Review.fromJson(snapshot.data());
return Padding(
padding: const EdgeInsets.only(bottom: 10.0),
child: Posts(post: posts),
);
},
),
ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemBuilder: (context, index) {
return Column(
children: [
if (index % 3 == 0 && index != 0)
AdWidget(ad: ad)
],);})
]));
}
This is my first time working with flutter, and i am new to coding. I am trying to display the bannerAds, however, they do not show and no log is displayed. This is probably due to the render error I have:
The following _CastError was thrown during paint():
Null check operator used on a null value
The relevant error-causing widget was:
ListView
When the exception was thrown, this was the stack:
#0 RenderViewportBase._paintContents
(package:flutter/src/rendering/viewport.dart:653:25)
#1 RenderViewportBase.paint
(package:flutter/src/rendering/viewport.dart:645:7)
#2 RenderObject._paintWithContext
(package:flutter/src/rendering/object.dart:2317:7)
#3 PaintingContext._repaintCompositedChild
(package:flutter/src/rendering/object.dart:139:11)
#4 PaintingContext.repaintCompositedChild
(package:flutter/src/rendering/object.dart:100:5)
...
The following RenderObject was being processed when the exception was
fired:
RenderViewport#ae00e
... needs compositing
... parentData: <none> (can use size)
... constraints: BoxConstraints(w=360.0, h=507.0)
... layer: OffsetLayer#0dfc7 DETACHED
... engine layer: Null#007db
... offset: Offset(0.0, 0.0)
... size: Size(360.0, 507.0)
... axisDirection: down
... crossAxisDirection: right
... offset: ScrollPositionWithSingleContext#1c5d2(offset: 0.0, range:
null..null, viewport: 507.0, ScrollableState,
AlwaysScrollableScrollPhysics
-> ClampingScrollPhysics -> RangeMaintainingScrollPhysics,
IdleScrollActivity#40f4c, ScrollDirection.idle)
I am confused with the widgets and views. Help me, please! Thank you!

Answer 1

i didn't understand clearly what you re doing, i assume you re doing this wrong way,I edited the whole code this may help .
#override
Widget build(BuildContext context) {
return Expanded(
child: StreamBuilder(
stream: postRef
.where("bookmarks",
arrayContains: FirebaseAuth.instance.currentUser!.uid)
.orderBy('timestamp', descending: true)
.snapshots(),
builder: (_, DocumentSnapshot snapshot) {
if (snapshot.hasData) {
return ListView.separated(itemCount: snapshot.data.docs.length,
itemBuilder: (
context,
index,
) {
internetChecker(context);
Review posts = Review.fromJson(snapshot.data());
return Padding(
padding: const EdgeInsets.only(bottom: 10.0),
child: Posts(post: posts),
);
}, separatorBuilder: (context, index) {
if (index % 3 == 0 && index != 0)
return
AdWidget(ad: ad);
}, );
}else if (snapshot.hasError) {
return Center(
child: Text("error"),
);
} else {
return Center(
child: Text("loading"),
);
}
},
),);