Question

当我通过页面传递id（整数数据）时，我收到一条错误消息，提示genre_id为null。因此，当我使用索引作为变量将id传递到下一页时，出现了问题。如何使用索引将其作为下一页的ID传递？

在我使用的sqlite数据库中，我有一个tbl_genres和一个tbl_books，这些书的条目都通过genre_id（两个表中的一列）绑定到类型表。

@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(),
    );
  }

这是我的下一页...

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(),
    );
  }
}

还有如何在rawQuery中使用该索引来显示仅与该ID有关的信息？

Answer 1

如下修改您的第二页：

window.history.go(-1-n)

在rawQuery Dart中传递数据

1 个答案: