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NSUserDefaults on iOS and SharedPreferences on android,
providing a persistent store for simple data.
to add the shared_preferences package as a dependency, run flutter pub add:
<code_start>
import 'package:shared_preferences/shared_preferences.dart';
<code_end>
to implement persistent data, use the setter methods
provided by the SharedPreferences class.
setter methods are available for various primitive
types, such as setInt, setBool, and setString.
to read data, use the appropriate getter method provided
by the SharedPreferences class. for each
setter there is a corresponding getter method,
for example, getInt, getBool, and getString.
<code_start>
future<void> updateCounter() async {
final prefs = await SharedPreferences.getInstance();
int? counter = prefs.getInt('counter');
if (counter is int) {
await prefs.setInt('counter', ++counter);
}
setState(() {
_counter = counter;
});
}
<code_end>
<topic_end>
<topic_start>
routing
most apps contain several screens for displaying different
types of information. for example, you might have a product
screen that displays images where users could tap on a product
image to get more information about the product on a new screen.
in android, new screens are new activities.
in iOS, new screens are new ViewControllers. in flutter,
screens are just widgets! and to navigate to new
screens in flutter, use the navigator widget.
<topic_end>
<topic_start>
how do i navigate between screens?
in react native, there are three main navigators:
StackNavigator, TabNavigator, and DrawerNavigator.
each provides a way to configure and define the screens.
in flutter, there are two main widgets used to navigate between screens:
a navigator is defined as a widget that manages a set of child
widgets with a stack discipline. the navigator manages a stack
of route objects and provides methods for managing the stack,
like navigator.push and navigator.pop.
a list of routes might be specified in the MaterialApp widget,
or they might be built on the fly, for example, in hero animations.
the following example specifies named routes in the MaterialApp widget.
info note
named routes are no longer recommended for most
applications. for more information, see
limitations in the navigation overview page.
<code_start>
class NavigationApp extends StatelessWidget {
// this widget is the root of your application.
const NavigationApp({super.key});
@override
widget build(BuildContext context) {
return MaterialApp(
//...
routes: <string, WidgetBuilder>{
'/a': (context) => const UsualNavScreen(),
'/b': (context) => const DrawerNavScreen(),
},
//...
);
}
}
<code_end>
to navigate to a named route, the navigator.of()
method is used to specify the BuildContext
(a handle to the location of a widget in the widget tree).
the name of the route is passed to the pushNamed function to
navigate to the specified route.
<code_start>
Navigator.of(context).pushNamed('/a');
<code_end>
you can also use the push method of navigator which
adds the given route to the history of the
navigator that most tightly encloses the given BuildContext,
and transitions to it. in the following example,
the MaterialPageRoute widget is a modal route that
replaces the entire screen with a platform-adaptive
transition. it takes a WidgetBuilder as a required parameter.
<code_start>
navigator.push(
context,
MaterialPageRoute(
builder: (context) => const UsualNavScreen(),
),
);
<code_end>
<topic_end>
<topic_start>
how do i use tab navigation and drawer navigation?
in material design apps, there are two primary options
for flutter navigation: tabs and drawers.