How to fix "A dismissed Dismissible widget is still part of the tree." error in flutter

Question

I am building a fluter app with dismissible widget, firebase and StreamBuilder and getting following error "A dismissed Dismissible widget is still part of the tree."

Please find the below code sniped for the same.

Expanded(
                  child: StreamBuilder(
                    stream: Firestore.instance
                        .document('/users/User1/Trips/${widget.tripId}')
                        .collection('TropDocs')
                        .snapshots(),
                    builder: (context, snapshot) {
                      if (!snapshot.hasData) return const Text("Loading....");
                      return ListView.builder(
                        itemExtent: 150.0,
                        itemCount: snapshot.data.documents.length,
                        itemBuilder: (context, index) {

final item = snapshot.data.documents[index];
                          final itemID =
                              snapshot.data.documents[index].documentID;
                          final list = snapshot.data.documents;      
return Dismissible(
   key: Key(itemID),
              // We also need to provide a function that tells our app
              // what to do after an item has been swiped away.
              onDismissed: (direction) {
                // Remove the item from our data source.

                //fBtDoc.deleteTraveldoc(item);
                //Firestore.instance.collection('/users/User1/Trips/${widget.tripId}/TropDocs/').document('$itemID').delete();
                setState(() {
                  list.removeAt(index);
                });

                // Then show a snackbar!
                Scaffold.of(context)
                    .showSnackBar(SnackBar(content: Text("$item dismissed")));
              },
              // Show a red background as the item is swiped away
              background: Container(color: Colors.red),
              child: _buildlistitem(
                            context, snapshot.data.documents[index])
);

                        }
                      );
                    },
                  ),
                )

Answer 1

Probably, I'm late, but I think it will be helpful for others. Had the same problem and even setting

key: Key(itemId[index]),

didn't work. However,

key: UniqueKey(),

worked perfectly for me

Answer 2

I think that's because you are trying to use same key for every dismissible.

key: Key(itemID)

It should be key: Key(itemID[index])

Answer 3

In my cause, I have used as below

key: Key(index),

and then I did change it as below. It's working

key: UniqueKey(),