【Flutter】shared_ Preferences local storage (introduction | install the shared_preferences plug-in | use the shared_preferences process)

One 、shared_preferences Introduction to local storage plug-ins

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shared_preferences yes Flutter Provided Local data access plug-in unit ;

On different platforms , Develop based on different mechanisms , Such as Android Based on SharedPreferences Development , iOS Based on NSUserDefaults Development ;

Accessing local files is a time-consuming operation , Therefore access shared_preferences Storage is a Asynchronous operations ;

Two 、 install shared_preferences plug-in unit

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install shared_preferences plug-in unit :

shared_preferences Plug-in address : https://pub.dev/packages/shared_preferences

according to https://pub.dev/packages/shared_preferences/install Address the installation tutorial to install ;

First , stay pubspec.yaml In profile , Import plug-in package :

dependencies:  shared_preferences: ^2.0.7

then , Download the plug-in package , Click on Pub Get Button , Download the plug-in package into this project ;

Last , stay Dart Import the following code into the code , You can use shared_preferences ;

import 'package:shared_preferences/shared_preferences.dart';

3、 ... and 、 Use shared_preferences technological process

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After completing the above installation shared_preferences After the plug-in , To start using ;

First , Import plug-in package ;

import 'package:shared_preferences/shared_preferences.dart';

then , obtain shared_preferences example ;

final prefs = await SharedPreferences.getInstance();

Last , Through the above shared_preferences Instances can Set up / Read Stored key value pair value ;

///  Set the value prefs.setInt('counter', counter);///  Get value  final counter = prefs.getInt('counter') ?? 0;}

If you want to delete data , call shared_preferences Example of remove Method ;

prefs.remove('counter');

The picture below is Flutter Of SharedPreferences Class , Focus on data access methods ;

Data storage example :

  _setValue() async { 
        ///  First get  SharedPreferences  example     SharedPreferences prefs = await SharedPreferences.getInstance();    setState(() { 
          textInfo = ' Save string  "  Xiao Wang  "  To  shared_preferences  complete ';    });    ///  Save data to  SharedPreferences  in     await prefs.setString("name", " Xiao Wang ");  }

Data access examples :

  _getValue() async { 
        ///  First get  SharedPreferences  example     SharedPreferences prefs = await SharedPreferences.getInstance();    ///  from  SharedPreferences  get data     String? name = await prefs.getString("name");    setState(() { 
          textInfo = ' from  shared_preferences  Take out the data  " ${name} "';    });  }

Four 、 Complete code example

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import 'package:flutter/material.dart';import 'package:shared_preferences/shared_preferences.dart';void main() { 
      runApp(MyApp());}class MyApp extends StatefulWidget { 
      const MyApp({ 
    Key? key}) : super(key: key);  @override  _MyAppState createState() => _MyAppState();}class _MyAppState extends State<MyApp> { 
      String textInfo = " Click the button to save the data to  shared_preferences  in ";  _setValue() async { 
        ///  First get  SharedPreferences  example     SharedPreferences prefs = await SharedPreferences.getInstance();    setState(() { 
          textInfo = ' Save string  "  Xiao Wang  "  To  shared_preferences  complete ';    });    ///  Save data to  SharedPreferences  in     await prefs.setString("name", " Xiao Wang ");  }  _getValue() async { 
        ///  First get  SharedPreferences  example     SharedPreferences prefs = await SharedPreferences.getInstance();    ///  from  SharedPreferences  get data     String? name = await prefs.getString("name");    setState(() { 
          textInfo = ' from  shared_preferences  Take out the data  " ${name} "';    });  }  @override  Widget build(BuildContext context) { 
        return MaterialApp(      home: Scaffold(        appBar: AppBar(          title: Text("shared_preferences  The data access "),        ),        body: Column(          children: [            Text(textInfo),            ElevatedButton(              onPressed: (){ 
                    _setValue();              },              child: Text(" Store data to  shared_preferences  in "),            ),            ElevatedButton(              onPressed: (){ 
                    _getValue();              },              child: Text(" from  shared_preferences  Get data in "),            ),          ],        ),      ),    );  }}

Execution results :

5、 ... and 、 Related resources

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Reference material :

• Flutter Official website : https://flutter.dev/
• Flutter Plug in download address : https://pub.dev/packages
• Flutter Developing documents : https://flutter.cn/docs ( Strongly recommend )
• official GitHub Address : https://github.com/flutter
• Flutter The Chinese community : https://flutter.cn/
• Flutter Practical tutorial : https://flutter.cn/docs/cookbook
• Flutter CodeLab : https://codelabs.flutter-io.cn/
• Dart Chinese document : https://dart.cn/
• Dart Developer website : https://api.dart.dev/
• Flutter Chinese net : https://flutterchina.club/ , http://flutter.axuer.com/docs/
• Flutter Related issues : https://flutterchina.club/faq/ ( It is recommended to watch it at the introductory stage )
• GitHub Upper Flutter Open source examples : https://download.csdn.net/download/han1202012/15989510
• Flutter Practical e-books : https://book.flutterchina.club/chapter1/
• Dart Language practice website : https://dartpad.dartlang.org/

Important topics :

• Flutter Animation reference documentation : https://flutterchina.club/animations/

Blog source download :

• GitHub Address : https://github.com/han1202012/flutter_shared_preferences ( Keep updating with the progress of the blog , There may not be the source code of this blog )

• Blog source snapshot : ( The source code snapshot of this blog , You can find the source code of this blog )