Flutter - list duplicates old and new values - firebase

Question

I have a method for receiving push from Firebase Cloud Messaging, and within it, the notification is allocated within a list. What happens is that this method is making the old value a duplicate of the new value.
Firebase method:
FirebaseMessaging.onMessage.listen((RemoteMessage message) async {
if (message.notification != null) {
widget._localNotificationList.title = message.notification.title;
widget._localNotificationList.body = message.notification.body;
widget._pushDecode.notifList.add(widget._localNotificationList);
savePush(); //this method maintains notification on the user's screen, with sharedPreferences
setState(() {});
}
});
Page View:
ListView.builder(
itemCount: widget._pushDecode.notifList.length,
itemBuilder: (context, i) {
return Card(
margin: EdgeInsets.all(10),
elevation: 4,
child: ListTile(
trailing: IconButton(
icon: Icon(Icons.delete),
onPressed: () => removePush(i),
),
title: Text(
widget._pushDecode.notifList.reversed.elementAt(i).title,
),
subtitle: Text(
widget._pushDecode.notifList.reversed.elementAt(i).body,
),
),
);
},
),

Answer 1

You need to use the key value because it does not know if the widget that was in the position you are adding it for example is different then the previous, but using keys he can always know that two widgets are different when they are the same type like your card.
ListView.builder(
itemCount: widget._pushDecode.notifList.length,
itemBuilder: (context, i) {
return Card(
key: UniqueKey(), // you can also use ValueKey('this must be unique for each element in the list.')
margin: EdgeInsets.all(10),
elevation: 4,
child: ListTile(
trailing: IconButton(
icon: Icon(Icons.delete),
onPressed: () => removePush(i),
),
title: Text(
widget._pushDecode.notifList.reversed.elementAt(i).title,
),
subtitle: Text(
widget._pushDecode.notifList.reversed.elementAt(i).body,
),
),
);
},
),