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Last Updated: Mar 27, 2024
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Flutter State Management

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Introduction

This section will talk about flutter state management and how to deal with it. We already know that everything in Flutter is a widget. The widget can be divided into two types: stateless widgets and stateful widgets. There is no internal state in the Stateless widget. It means we can't update or modify it once it's been built until they're initialized again. A Stateful widget, on the other hand, is dynamic and has a state. This means we can simply tweak it during its existence without reinitializing it.

State in flutter

A state is a data that may be read when the widget is created and may change or be adjusted over the app's lifetime. You must update the state object if you wish to change your widget, which you can do with the setState() function present for Stateful widgets. We may use the setState() function to change the attributes of the state entity that causes the UI to redraw.

                                 Source: suragch.medium

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State Management

One of the most valuable and famous activities in the lifespan of an application is state management. Flutter is declarative, according to the documentation. It signifies that Flutter's UI is based on the current state of your app. 

To grasp the notion of state management, consider the following example. Assume you've generated a customer or product list in your app. Suppose you've dynamically added a new client or product to that list. Then, to see the newly added item in the record, you must reload the list. As a result, you must reload the list whenever you add a new item. To boost performance, this sort of programming necessitates state management to manage such a situation. The state is updated every time you create a modification or update it.

Types of State Management

The state management in Flutter is divided into two categories, as listed below:

  1. Ephemeral State
  2. App State

Ephemeral State

This state is also known as the User Interface State (UI State) or the Local State. It is a form of state linked to a specific widget or a state contained within a single widget. You don't need to employ state management strategies in this situation. Text Field is a similar example of this condition.

 

Example: 

class MyHomepageState extends State<MyHomepage> {
  String _name = "Hey Ninja!!!!";

  @override

  Widget build(BuildContext context) {

    return RaisedButton(

      child: Text(_name),

      onPressed: () {

        setState(() {

          _name = _name == "Hey Ninja!!!!" ? "Coding Ninjas" : "Hey Ninja!!!!";

        });
      },
    );
  }
}

App State

It's not the same as the ephemeral state. It's a state that we want to preserve throughout user sessions and communicate across different portions of our app. As a result, this state type can be applied universally. It's also referred to as a shared state or application state. User preferences, login information, alerts in a social media app, the shopping basket in an e-commerce app, and so on are all examples of this state.

Using the provider package, you may study the most basic example of app state management. The provider's state management is simple to grasp and needs little code. A third-party library is a supplier. To use this library, we must first learn three key ideas.

  1. ChangeNotifier
  2. ChangeNotifierProvider
  3. Consumer

 

ChangeNotifier

ChangeNotifier is an introductory class that notifies its listeners when anything changes. It is simple to comprehend, implement, and optimize for a small group of listeners. It is utilized for the listener to notice a change model. We simply use the notifyListener() function to notify the listeners in this case.

 

Example:

import 'package:flutter/material.dart';  
  
class Counter with ChangeNotifier {  
  int _count;  
  
  Count(this._count);  
  
  getCount() => _count;  
  setCount(int count) => _count = count;  
  
  void increment() {  
    _count++;  
    notifyListeners();  
  }  
  
  void decrement() {  
    _count--;  
    notifyListeners();  
  }  
}  

 

ChangeNotifierProvider

ChangeNotifierProvider is a widget that delivers a ChangeNotifier instance to its children. It is part of the provider bundle. The code samples below will help you grasp the notion of ChangeNotifierProvider.

 

Example:

class MyApp extends StatelessWidget {  
  @override  
  Widget build(BuildContext context) {  
    return MaterialApp(  
      theme: ThemeData(  
        primarySwatch: Colors.blue,  
      ),  
      home: ChangeNotifierProvider<CountModel>(  
        builder: (_) => CountModel(),  
        child: CountView(),  
      ),  
    );  
  }  
}  

 

Consumer

It is a supplier who does not perform anything special. It invokes the provider in a new widget and passes the build implementation to the builder. The code below describes it in further detail.

 

Example:

return Consumer<Count>(  
  builder: (context, count, child) {  
    return Text("Total price: ${count.total}");  
  },  
);  

Code

Let us have a look at the complete code to show state management. Copy the code given below and paste it into the main.dart file.

 

Code:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // Root widget 
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Name of the Application
      title: 'Flutter  State Management(Coding Ninjas)',
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      home: MyHomepage(),
    );
  }
}

class MyHomepage extends StatefulWidget {
  @override
  MyHomepageState createState() => MyHomepageState();
}

class MyHomepageState extends State<MyHomepage> {
  String _name = "Hey Ninja!!!!";

  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      child: Text(_name),
      onPressed: () {
        setState(() {
          _name = _name == "Hey Ninja!!!!" ? "Coding Ninjas" : "Hey Ninja!!!!";
        });
      },
    );
  }
}

 

Output:

When you run the above code, you will see the output as given below:

Frequently Asked Questions

What is flutter?

Flutter is a framework that allows you to create entirely platform-agnostic mobile applications for iOS and Android.

What are the advantages of flutter?

The following are some of the advantages of using flutter:

  1. Cross-platform Development
  2. Reduce Code Development
  3. Live and Hot Reloading
  4. Flexible UI
  5. Good community support

What is a state in flutter?

A state is data that may be read when the widget is created and may change or be adjusted over the app's lifetime.

Explain state management in a flutter.

One of the most valuable and famous activities in the lifespan of an application is state management. State management is used to boost the overall performance of our application. 

What is Ephemeral State?

This state is also known as the User Interface State (UI State) or the Local State. It is a form of state linked to a specific widget or a state contained within a single widget.

Conclusion

In this article, we have extensively discussed Flutter state management and its uses. We looked at various categories of state management in the flutter.

After reading about Flutter State Management, are you not feeling excited to read/explore more articles on flutter? Don’t worry; Coding Ninjas has you covered. To learn, see Flutter basicsFlutter App Development, and Flutter navigation

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Topics covered
1.
Introduction
2.
State in flutter
3.
State Management
4.
Types of State Management
4.1.
Ephemeral State
4.2.
App State
5.
Code
6.
Frequently Asked Questions
6.1.
What is flutter?
6.2.
What are the advantages of flutter?
6.3.
What is a state in flutter?
6.4.
Explain state management in a flutter.
6.5.
What is Ephemeral State?
7.
Conclusion