Passing Data through in a rawQuery Dart - sqlite

Question

I am getting an error message saying that genre_id is null when I pass an id (integer data) through pages. So there is something wrong when I use the index as a variable to pass on an id to the next page. How do I use index to pass it as an id for the next page?
In my sqlite database that I am using, I have a tbl_genres and a tbl_books with the book entries being tied to the genre table with a genre_id (a column in both tables).
#override
Widget build(BuildContext context) {
return Scaffold(
body: !loading ? new ListView.builder(
itemCount: genreList.length,
itemBuilder: (BuildContext context, int index) {
return new Card(
child: new ListTile(
title: new Text("${genreList[index]}"),
onTap: () {
Navigator.push(context,
MaterialPageRoute(
builder: (context) =>
BookListPage(id: index), //how to pass index as an int?
),
);
}),
);
},
) : CircularProgressIndicator(),
);
}
Here is my next page...
class BookListPage extends StatefulWidget {
int id;
BookListPage({this.id});
#override
_BookListPageState createState() => _BookListPageState();
}
class _BookListPageState extends State<BookListPage> {
bool loading;
List<Map> bookNames;
final int id;
_BookListPageState({this.id});
void initState() {
super.initState();
loading = true;
getBookData();
}
Future getBookData() async {
print(id);
Directory documentsDirectory = await getApplicationDocumentsDirectory();
String path = join(documentsDirectory.path, "asset_sample_sqlite.db");
ByteData data = await rootBundle.load(join("assets", "sample_sqlite.db"));
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
await new File(path).writeAsBytes(bytes);
Database db = await openDatabase(path);
final _bookList = await db.rawQuery('SELECT book_name[] FROM tbl_books WHERE genre_id = $id'); //how to reference the passed id?
await db.close();
setState((){
loading = false;
bookNames = _bookList;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: !loading ? new ListView.builder(
itemCount: bookNames.length,
itemBuilder: (BuildContext context, int index) {
return new Card(
child: new ListTile(
title: new Text("${bookNames[index]}"),
),
);
}
) : CircularProgressIndicator(),
);
}
}
And also how do I use that index in the rawQuery to display information only relating to that id?

Answer 1

Modify your second page as follows:
class BookListPage extends StatefulWidget {
final int id;
BookListPage({this.id});
#override
_BookListPageState createState() => _BookListPageState();
}
class _BookListPageState extends State<BookListPage> {
bool loading;
List<Map> bookNames;
_BookListPageState();
void initState() {
super.initState();
loading = true;
getBookData();
}
Future getBookData() async {
print(widget.id);
Directory documentsDirectory = await getApplicationDocumentsDirectory();