Displaying Snackbar inside a SearchDelegate - flutter

Question

I am using a SearchDelegate and want to display a Snackbar when the user tries to perform a search with an empty query. I've tried returning Scaffold widgets from both the buildSuggestions and buildResults methods and then using a Builder / GlobalKey inside the buildResults method to display a message to the user if the search query has a length of zero. However this leads to the Scaffold's state being updated during the render method which throws an exception. Has anyone dealt with a similar challenge? Seems like a common use case that you would want to display a Snackbar inside your search delegate, yet I can't seem to fathom an easy way to do it.

Answer 1

Figured it out
class DataSearch extends SearchDelegate<String> {
List<Drug> drugList = new List<Drug>();
DataSearch(Future<List<Drug>> listDrugName) {
this.drugListFuture = listDrugName;
}
#override
List<Widget> buildActions(BuildContext context) {
// actions for app bar
return [
IconButton(
icon: Icon(Icons.clear),
onPressed: () {
query = "";
})
];
}
#override
Widget buildLeading(BuildContext context) {
// leading icon on the left of app bar
return IconButton(
icon: AnimatedIcon(
icon: AnimatedIcons.menu_arrow, progress: transitionAnimation),
onPressed: () {
close(context, null);
});
}
#override
Widget buildResults(BuildContext context) {
// show result from selection
return null;
}
#override
Widget buildSuggestions(BuildContext context) {
return new FutureBuilder(
future: db.getDrugEntries(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (!snapshot.hasData || snapshot.data.length < 1) {
return new Center(
child: new LoadingIndicator(Constants.msgLoading));
} else {
drugList = snapshot.data;
// show when user searches for something
final suggestionList = query.isEmpty
? drugList
: drugList
.where((r) =>
(r.drugId.toLowerCase())
.contains(query.toLowerCase()) ||
(r.fullDrugName.toLowerCase())
.contains(query.toLowerCase()) ||
(r.otherName.toLowerCase())
.contains(query.toLowerCase()) ||
(r.tradeName.toLowerCase())
.contains(query.toLowerCase()))
.toList();
return ListView.builder(
itemBuilder: (context, index) {
String drugName = suggestionList[index].genericName;
String drugId = suggestionList[index].drugId;
int queryIndex = drugName.indexOf(query);
if (queryIndex == -1) {
queryIndex = 0;
}
int queryIndexEnd = queryIndex + query.length;
return Container(button//...onTap:_launchExtraContent(context,drugId);
},
itemCount: suggestionList.length,
);
}
});
}
_
_launchExtraContent(BuildContext context, StringtheFileName) async {
try {
//......
} catch (e) {
_showSnackBar(context,'ERROR: Unable to retrieve file please submit a bug report');
}
}
void _showSnackBar(BuildContext context, String text) {
Scaffold.of(context).showSnackBar(new SnackBar(
content: new Text(
text,
textAlign: TextAlign.center,
),
backgroundColor: Colors.red,
));
}
}