【发布时间】：2020-11-15 18:17:46
【问题描述】：
我想在 Drawer 中使用带有 Switch 的 Dark/Light 主题。您可以在我的“drawerDosyasi.dart”中看到“Switch”。但首先我想在我的主页（Anasayfa）上用 SwitchListTile 编写代码。
两个问题：
1- 我现在遇到这个错误
错误：在此消费者小部件上方找不到正确的提供者
这可能是因为您使用了不包含提供程序的BuildContext
你的选择。有几种常见的情况：
-
您尝试读取的提供程序位于不同的路径中。
提供者是“范围的”。因此，如果您在路线内插入提供者，那么 其他路由将无法访问该提供程序。
-
您使用了
BuildContext，它是您尝试读取的提供程序的祖先。确保 Consumer 在您的 MultiProvider/Provider 下。 这通常发生在您创建提供程序并尝试立即读取它时。
例如，而不是：
Widget build(BuildContext context) { return Provider<Example>( create: (_) => Example(), // Will throw a ProviderNotFoundError, because `context` is associated // to the widget that is the parent of `Provider<Example>` child: Text(context.watch<Example>()), ), }考虑像这样使用
builder：Widget build(BuildContext context) { return Provider<Example>( create: (_) => Example(), // we use `builder` to obtain a new `BuildContext` that has access to the provider builder: (context) { // No longer throws return Text(context.watch<Example>()), } ), }
2- 我无法将开关移动到抽屉。给出关于转为 null 的错误。所以我希望能够在 DrawerHeader 中使用 Switch() 更改暗/亮模式
谁能修复我的代码？我是新手，两天解决不了问题。
anasayfa.dart
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (_) => ThemeNotifier(),
child: Consumer<ThemeNotifier>(
builder: (context, ThemeNotifier notifier, child) {
return MaterialApp(
title: 'Flutter Theme Provider',
theme: notifier.darkTheme ? dark : light,
home: Anasayfa(),
);
},
),
);
}
}
class Anasayfa extends StatefulWidget {
@override
_AnasayfaState createState() => _AnasayfaState();
}
class _AnasayfaState extends State<Anasayfa> {
int currentPage = 0;
nested() {
return NestedScrollView(
headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
return [
SliverAppBar(
toolbarHeight: 40,
expandedHeight: 92.0,
floating: false,
pinned: true,
flexibleSpace: FlexibleSpaceBar(
background: Image.asset(
"assets/images/besmele.jpg",
fit: BoxFit.cover,
),
),
actions: [
IconButton(
icon: Icon(Icons.account_circle),
color: Colors.white,
onPressed: () {},
),
],
)
];
},
body: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Consumer<ThemeNotifier>(
builder: (context, notifier, child) => SwitchListTile(
title: Text("Dark Mode"),
onChanged: (val) {
notifier.toggleTheme();
},
value: notifier.darkTheme,
),
),
],
),
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: nested(),
drawer: Drawer(
child: DrawerDosyasi(),
),
bottomNavigationBar: CurvedNavigationBar(
color: Colors.blue,
backgroundColor: Colors.white,
buttonBackgroundColor: Colors.blue,
height: 50,
items: <Widget>[
Icon(
Icons.campaign,
size: 20,
color: Colors.white,
),
Icon(
Icons.supervisor_account,
size: 20,
color: Colors.white,
),
Icon(
Icons.home,
size: 20,
color: Colors.white,
),
Icon(
Icons.video_collection_rounded,
size: 20,
color: Colors.white,
),
Icon(
Icons.menu_book_rounded,
size: 20,
color: Colors.white,
),
],
animationDuration: Duration(
milliseconds: 300,
),
index: 2,
animationCurve: Curves.bounceInOut,
onTap: (index) {
debugPrint("Current index is $index");
},
),
);
}
}
drawerDosyasi.dart
class DrawerDosyasi extends StatefulWidget {
@override
_DrawerDosyasiState createState() => _DrawerDosyasiState();
}
class _DrawerDosyasiState extends State<DrawerDosyasi> {
@override
Widget build(BuildContext context) {
return Container(
child: ListView(
padding: EdgeInsets.zero,
children: <Widget>[
DrawerHeader(
decoration: BoxDecoration(
color: Colors.blue,
),
child: Row(
children: [
Expanded(
flex: 1,
child: Switch(),
),
Expanded(
flex: 3,
child: CircleAvatar(
radius: 60,
backgroundColor: Colors.white,
),
),
Expanded(flex: 1, child: SizedBox.expand()),
],
),
),
ListTile(
leading: Icon(Icons.home),
title: Text('Anasayfa'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.account_circle),
title: Text('Profil'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.campaign),
title: Text('Duyurular'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.account_box),
title: Text('Hocalar'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.library_books),
title: Text('Dergiler'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.video_collection_rounded),
title: Text('Canlı Dersler'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.menu_book_rounded),
title: Text('Kütüphane'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.supervisor_account),
title: Text('Tartışmalar'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.create),
title: Text('Yazı Gönder'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.message_rounded),
title: Text('İletişim'),
tileColor: Colors.white,
),
ListTile(
leading: Icon(Icons.exit_to_app_rounded),
title: Text('Çıkış'),
tileColor: Colors.white,
),
],
),
);
}
}
theme.dart
ThemeData light = ThemeData(
brightness: Brightness.light,
primarySwatch: Colors.blue,
accentColor: Colors.blue,
scaffoldBackgroundColor: Color(0xfff1f1f1));
ThemeData dark = ThemeData(
brightness: Brightness.dark,
primarySwatch: Colors.indigo,
accentColor: Colors.green[700],
);
class ThemeNotifier extends ChangeNotifier {
final String key = "theme";
SharedPreferences _prefs;
bool _darkTheme;
bool get darkTheme => _darkTheme;
ThemeNotifier() {
_darkTheme = true;
_loadFromPrefs();
}
toggleTheme() {
_darkTheme = !_darkTheme;
_saveToPrefs();
notifyListeners();
}
_initPrefs() async {
if (_prefs == null) _prefs = await SharedPreferences.getInstance();
}
_loadFromPrefs() async {
await _initPrefs();
_darkTheme = _prefs.getBool(key) ?? true;
notifyListeners();
}
_saveToPrefs() async {
await _initPrefs();
_prefs.setBool(key, _darkTheme);
}
}
【问题讨论】：
标签： android flutter dart switch-statement android-dark-theme