What is Difference Between StreamBuilder and FutureBuilder In Flutter

hii I hope you all are well and doing something better in your life. so this time we understand what are StreamBuilder and FutureBuilder, how and when we use them.

Introduction

Flutter, the popular cross-platform framework, provides developers with two powerful widgets for handling asynchronous operations: StreamBuilder and FutureBuilder. Although they share similarities, it’s crucial to understand their differences to choose the appropriate one for your specific use case. In this blog post, we’ll dive into the characteristics and usage of both widgets, providing you with a comprehensive understanding of when to use each.

Introducing FutureBuilder

To begin, let’s explore FutureBuilder, which is designed for handling asynchronous operations that return a single value in the future. Follow these steps to leverage the power of FutureBuilder:

1. FutureBuilder is used when you have a one-time asynchronous operation that returns a value, such as an HTTP request or reading from a file.
2. Import the required dependencies: import 'dart:async';.
3. Create a Future an object that represents the asynchronous operation you want to perform. For example, you can use http.get() it to make an HTTP request and get a response.
4. Wrap the section of your UI that depends on the future result inside a FutureBuilder widget.
5. Pass the future object to the FutureBuilder using the future parameter.
6. Implement the builder callback function of the FutureBuilder widget. This function will be called when the future completes and returns a result.
7. Inside the builder function, access the snapshot of the future result using snapshot.data.
8. Based on the state of the snapshot (ConnectionState and AsyncSnapshot), you can handle different UI states such as data loading, error handling, or displaying the actual result.
9. Update your UI with the future result by accessing snapshot.data the builder function.

you better understand the code so there it is.

open your main.dart file and implement this code and see the output of what is happening.

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: HomePage()));

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int _count = 0; // used by StreamBuilder

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('StreamBuilder VS FutureBuilder',style: TextStyle(fontSize: 18,color: Colors.black),),
        centerTitle: true,
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          _buildFutureBuilder(),

        ],
      ),
    );
  }

  // constructing FutureBuilder
  Widget _buildFutureBuilder() {
    return Center(
      child: FutureBuilder<int>(
        future: _calculateSquare(10),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done)
            return Text("Square = ${snapshot.data}",style: TextStyle(fontSize: 20,color: Colors.purple),);

          return CircularProgressIndicator(color: Colors.green,);
        },
      ),
    );
  }

  // used by FutureBuilder
  Future<int> _calculateSquare(int num) async {
    await Future.delayed(Duration(seconds: 5));
    return num * num;
  }
  
}

Output:

Introducing StreamBuilder:

Moving on, let’s discuss StreamBuilder, which is suitable for handling asynchronous operations that produce multiple values over time. Follow these steps to implement StreamBuilder effectively:

1. StreamBuilder is used when you have a stream of asynchronous data that can change over time, such as real-time updates from a database or web service.
2. Import the required dependencies: import 'dart:async';.
3. Create a Stream an object that represents the data stream you want to listen to. It could be an instance of StreamController, or you can use built-in streams like Stream.fromFuture or Stream.periodic.
4. Wrap the section of your UI that depends on the stream data inside a StreamBuilder widget.
5. Pass the stream object to the StreamBuilder using the stream parameter.
6. Implement the builder callback function of the StreamBuilder widget. This function will be called whenever new data is emitted by the stream.
7. Inside the builder function, access the snapshot of the stream data using snapshot.data.
8. Based on the state of the snapshot (ConnectionState), you can show different UI states such as data loading, error handling, or displaying the actual data.
9. Update your UI whenever the stream emits new data by accessing snapshot.data inside the builder function.

Ok if you see the code then you better understand what I am saying

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: HomePage()));

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int _count = 0; // used by StreamBuilder

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('StreamBuilder VS FutureBuilder',style: TextStyle(fontSize: 18,color: Colors.black),),
        centerTitle: true,
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          _buildStreamBuilder(),
        ],
      ),
    );
  }

  // constructing StreamBuilder
  Widget _buildStreamBuilder() {
    return Center(
      child: StreamBuilder<int>(
        stream: _stopwatch(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.active)
            return Text("Stopwatch = ${snapshot.data}",style: TextStyle(fontSize: 20,color: Colors.orange),);
          return CircularProgressIndicator();
        },
      ),
    );
  }
  // used by StreamBuilder
  Stream<int> _stopwatch() async* {
    while (true) {
      await Future.delayed(Duration(seconds: 1));
      yield _count++;
    }
  }
}

Output:

Conclusion:

In conclusion, both StreamBuilder and FutureBuilder are important widgets in Flutter for handling asynchronous operations and updating the UI based on the resulting data. Here’s a summary of their characteristics:

StreamBuilder:

• Used for continuous streams of data that can change over time.
• Suitable for real-time updates, such as database or web service changes.
• Requires an Stream object to listen to the data stream.
• The builder the function is called whenever new data is emitted by the stream.
• Allows you to handle different UI states based on the state of the stream (ConnectionState) and access the data using snapshot.data.

FutureBuilder:

• Used for one-time asynchronous operations that return a value.
• Suitable for operations like HTTP requests or reading from files.
• Requires a Future object that represents the asynchronous operation.
• The builder function is called when the future completes and returns a result.
• Enables you to handle different UI states based on the state of the future (ConnectionState and AsyncSnapshot) and access the result using snapshot.data.

Both widgets serve similar purposes, but the key distinction lies in the nature of the asynchronous operations they handle. StreamBuilder is used for continuous streams that can emit multiple data events over time, while FutureBuilder is used for one-time operations that produce a single result.

Understanding when to use each widget is crucial for efficient and responsive Flutter app development. By leveraging the appropriate widget, you can effectively handle asynchronous data and provide a seamless user experience.

I hope now you understand what are StreamBuilder and FutureBuilder and why and where we use them.

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