问题描述
我已经创建了 List< String>favId = [];
变量用于存储具有SharedPreferences的商品ID,因此在重新启动应用程序后,收藏的商品ID不会丢失.这是我的SharedPreferences方法和最喜欢的IconButton的详细信息.
I've create List<String> favId = [];
variable to store item's ID with SharedPreferences, so the favorited items ID didnt lost after I restart the application. And here is my SharedPreferences method and favorite IconButton in detailDoaPage.dart :
...
static List<String> favId = [];
getData() async {
SharedPreferences pref = await SharedPreferences.getInstance();
setState(() {
favId = pref.getStringList("id") ?? [];
});
}
void initState() {
super.initState();
getIds();
}
getIds() async {
favId = getData();
}
void saveData() async {
SharedPreferences pref = await SharedPreferences.getInstance();
pref.setStringList("id", favId);
}
...
IconButton(
icon: Icon(
favId.contains(doa.id.toString())
? Icons.favorite
: Icons.favorite_border,
color: favId.contains(doa.id.toString())
? Colors.red
: Colors.grey,
),
onPressed: () => setState(() {
doa.fav = !doa.fav;
if (favId.contains(doa.id.toString())) {
favId.removeWhere(
(element) => element == doa.id.toString());
} else {
favId.add(doa.id.toString());
}
saveData();
favId.sort();
}),
)
除此之外,我还想在favPage.dart(另一页)中使用ListView.builder显示喜欢的项目.当然,我想从detailDoaPage.dart获取favId.如何在这两个页面中实施提供者/河流脚架?
Beside that, I also want to show the favorited item's with ListView.builder in favPage.dart (another page). Of course I want get the favId from detailDoaPage.dart. How can I implement the provider/riverpod across this 2 pages?
这是我的应用程序的预览:
Here is the preview of my app :
谢谢:)
推荐答案
我建议的方法是创建一个StateNotifier来处理状态以及与SharedPreferences的交互.以下内容也简化了小部件中的逻辑.
My recommended approach would be to create a StateNotifier that handles the state as well as the interactions with SharedPreferences. The following simplifies the logic in your widgets as well.
final sharedPrefs =
FutureProvider<SharedPreferences>((_) async => await SharedPreferences.getInstance());
class FavoriteIds extends StateNotifier<List<String>> {
FavoriteIds(this.pref) : super(pref?.getStringList("id") ?? []);
static final provider = StateNotifierProvider<FavoriteIds, List<String>>((ref) {
final pref = ref.watch(sharedPrefs).maybeWhen(
data: (value) => value,
orElse: () => null,
);
return FavoriteIds(pref);
});
final SharedPreferences? pref;
void toggle(String favoriteId) {
if (state.contains(favoriteId)) {
state = state.where((id) => id != favoriteId).toList();
} else {
state = [...state, favoriteId];
}
// Throw here since for some reason SharedPreferences could not be retrieved
pref!.setStringList("id", state);
}
}
用法:
class DoaWidget extends ConsumerWidget {
const DoaWidget({Key? key, required this.doa}) : super(key: key);
final Doa doa;
@override
Widget build(BuildContext context, ScopedReader watch) {
final favoriteIds = watch(FavoriteIds.provider);
return IconButton(
icon: favoriteIds.contains('') ? Icon(Icons.favorite) : Icon(Icons.favorite_border),
color: favoriteIds.contains('') ? Colors.red : Colors.grey,
onPressed: () => context.read(FavoriteIds.provider.notifier).toggle(doa.id.toString()),
);
}
}
这篇关于Flutter:如何将Riverpod与SharedPreference和List< String>一起使用多页变量?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!