我对Flutter和Dart非常初学。所以我试图更新父小部件的状态,但说实话,在尝试了许多不同的解决方案后,没有一个适用于我,或者我做错了什么吗?
我想要做的是在_Books()类中更改页面时更新_BooksState()中的_title。
我该如何从子(_Books())小部件设置_title状态?
class Books extends StatefulWidget {
@override
_BooksState createState() {
return _BooksState();
}
}
class _BooksState extends State<Books> {
String _title = 'Books';
_setTitle(String newTitle) {
setState(() {
_title = newTitle;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(_title),
),
body: _Books(),
);
}
}
class _Books extends StatelessWidget {
final PageController _controller = PageController();
final Stream<QuerySnapshot> _stream =
Firestore.instance.collection('Books').orderBy('title').snapshots();
_setAppBarTitle(String newTitle) {
print(newTitle);
// how do I set _title from here?
}
@override
Widget build(BuildContext context) {
return StreamBuilder<QuerySnapshot>(
stream: _stream,
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
final books = snapshot.data.documents;
switch (snapshot.connectionState) {
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
default:
return PageView.builder(
controller: _controller,
scrollDirection: Axis.horizontal,
itemCount: books.length,
itemBuilder: (context, index) {
final book = books[index];
return ListTile(
title: Text(book['title']),
subtitle: Text(book['author']),
);
},
onPageChanged: (index) {
_setAppBarTitle(books[index].data['title']);
},
);
}
},
);
}
}