If you have a relatively small collection of key-values to save, you can use theshared_preferences plugin.

Normally, you would have to write native platform integrations for storing data on each platform. Fortunately, theshared_preferences plugin can be used to persist key-value data to disk on each platform Flutter supports.

This recipe uses the following steps:

1. Add the dependency.
2. Save data.
3. Read data.
4. Remove data.

Before starting, add theshared_preferences package as a dependency.

To add theshared_preferences package as a dependency, runflutter pub add:

flutter pub add shared_preferences

To persist data, use the setter methods provided by theSharedPreferences class. Setter methods are available for various primitive types, such assetInt,setBool, andsetString.

Setter methods do two things: First, synchronously update the key-value pair in memory. Then, persist the data to disk.

// Load and obtain the shared preferences for this app.finalprefs=awaitSharedPreferences.getInstance();​// Save the counter value to persistent storage under the 'counter' key.awaitprefs.setInt('counter',counter);

To read data, use the appropriate getter method provided by theSharedPreferences class. For each setter there is a corresponding getter. For example, you can use thegetInt,getBool, andgetString methods.

finalprefs=awaitSharedPreferences.getInstance();​// Try reading the counter value from persistent storage.// If not present, null is returned, so default to 0.finalcounter=prefs.getInt('counter')??0;

Note that the getter methods throw an exception if the persisted value has a different type than the getter method expects.

To delete data, use theremove() method.

finalprefs=awaitSharedPreferences.getInstance();​// Remove the counter key-value pair from persistent storage.awaitprefs.remove('counter');

Although the key-value storage provided byshared_preferences is easy and convenient to use, it has limitations:

• Only primitive types can be used:int,double,bool,String, andList<String>.
• It's not designed to store large amounts of data.
• There is no guarantee that data will be persisted across app restarts.

It's a good idea to test code that persists data usingshared_preferences. To enable this, the package provides an in-memory mock implementation of the preference store.

To set up your tests to use the mock implementation, call thesetMockInitialValues static method in asetUpAll() method in your test files. Pass in a map of key-value pairs to use as the initial values.

SharedPreferences.setMockInitialValues(<String,Object>{'counter':2});

import'package:flutter/material.dart';import'package:shared_preferences/shared_preferences.dart';​voidmain()=>runApp(constMyApp());​classMyAppextendsStatelessWidget{constMyApp({super.key});​@overrideWidgetbuild(BuildContextcontext){returnconstMaterialApp(title:'Shared preferences demo',home:MyHomePage(title:'Shared preferences demo'),);}}​classMyHomePageextendsStatefulWidget{constMyHomePage({super.key,requiredthis.title});​finalStringtitle;​@overrideState<MyHomePage>createState()=>_MyHomePageState();}​class_MyHomePageStateextendsState<MyHomePage>{int_counter=0;​@overridevoidinitState(){super.initState();_loadCounter();}​/// Load the initial counter value from persistent storage on start,/// or fallback to 0 if it doesn't exist.Future<void>_loadCounter()async{finalprefs=awaitSharedPreferences.getInstance();setState((){_counter=prefs.getInt('counter')??0;});}​/// After a click, increment the counter state and/// asynchronously save it to persistent storage.Future<void>_incrementCounter()async{finalprefs=awaitSharedPreferences.getInstance();setState((){_counter=(prefs.getInt('counter')??0)+1;prefs.setInt('counter',_counter);});}​@overrideWidgetbuild(BuildContextcontext){returnScaffold(appBar:AppBar(title:Text(widget.title)),body:Center(child:Column(mainAxisAlignment:MainAxisAlignment.center,children:[constText('You have pushed the button this many times:'),Text('$_counter',style:Theme.of(context).textTheme.headlineMedium,),],),),floatingActionButton:FloatingActionButton(onPressed:_incrementCounter,tooltip:'Increment',child:constIcon(Icons.add),),);}}