What are packages and plugins in Flutter?

Overview

Packages and Plugins are reusable code libraries in Flutter. The key difference is that packages contain pure Dart code, while plugins include platform-specific native code (Android/iOS).

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Comparison Table

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Packages

What is a Package?

A package contains pure Dart code that runs on any platform.

Examples

• provider - State management
• http - HTTP networking
• intl - Internationalization
• uuid - UUID generation
• equatable - Value equality

Installation

yamlCopy
dependencies:
  provider: ^6.0.5
  http: ^1.1.0
  intl: ^0.18.0

Usage Example

dartCopy
import 'package:http/http.dart' as http;
import 'package:provider/provider.dart';

// Pure Dart code - works everywhere
Future<void> fetchData() async {
  final response = await http.get(Uri.parse('https://api.example.com'));
  print(response.body);
}

// State management with provider
class Counter with ChangeNotifier {
  int _count = 0;
  
  int get count => _count;
  
  void increment() {
    _count++;
    notifyListeners();
  }
}

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Plugins

What is a Plugin?

A plugin includes Dart code + platform-specific native code to access device features.

Examples

• camera - Camera access
• battery - Battery info
• location - GPS location
• shared_preferences - Local storage
• url_launcher - Open URLs
• image_picker - Pick images

Installation

yamlCopy
dependencies:
  camera: ^0.10.5
  battery_plus: ^4.0.0
  geolocator: ^10.0.0
  shared_preferences: ^2.2.0

Usage Example

dartCopy
import 'package:battery_plus/battery_plus.dart';
import 'package:geolocator/geolocator.dart';
import 'package:shared_preferences/shared_preferences.dart';

// Access battery (native Android/iOS code)
Future<int> getBatteryLevel() async {
  final battery = Battery();
  return await battery.batteryLevel;
}

// Access GPS (native code)
Future<Position> getCurrentLocation() async {
  return await Geolocator.getCurrentPosition();
}

// Local storage (native SharedPreferences/UserDefaults)
Future<void> saveData(String key, String value) async {
  final prefs = await SharedPreferences.getInstance();
  await prefs.setString(key, value);
}

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How Plugins Work

Architecture

textCopy
┌────────────────────────────────────────┐
│  Flutter App (Dart)                    │
│  ↓                                     │
│  Plugin Dart Code                      │
│  ↓                                     │
│  Platform Channel (MethodChannel)     │
└────────────────────────────────────────┘
         ↓                    ↓
┌──────────────────┐  ┌──────────────────┐
│  Android         │  │  iOS             │
│  (Kotlin/Java)   │  │  (Swift/Obj-C)   │
│  ↓               │  │  ↓               │
│  Native APIs     │  │  Native APIs     │
└──────────────────┘  └──────────────────┘

Platform Channel Example

Dart side:

dartCopy
import 'package:flutter/services.dart';

class BatteryPlugin {
  static const platform = MethodChannel('com.example/battery');
  
  Future<int> getBatteryLevel() async {
    try {
      final int result = await platform.invokeMethod('getBatteryLevel');
      return result;
    } catch (e) {
      return -1;
    }
  }
}

Android side (Kotlin):

kotlinCopy
class MainActivity: FlutterActivity() {
  private val CHANNEL = "com.example/battery"
  
  override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
    MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL)
      .setMethodCallHandler { call, result ->
        if (call.method == "getBatteryLevel") {
          val batteryLevel = getBatteryLevel()
          result.success(batteryLevel)
        }
      }
  }
  
  private fun getBatteryLevel(): Int {
    val batteryManager = getSystemService(Context.BATTERY_SERVICE) as BatteryManager
    return batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)
  }
}

iOS side (Swift):

swiftCopy
@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(_ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    
    let controller = window?.rootViewController as! FlutterViewController
    let batteryChannel = FlutterMethodChannel(name: "com.example/battery",
                                              binaryMessenger: controller.binaryMessenger)
    
    batteryChannel.setMethodCallHandler({
      (call: FlutterMethodCall, result: @escaping FlutterResult) -> Void in
      if call.method == "getBatteryLevel" {
        self.getBatteryLevel(result: result)
      }
    })
    
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
  
  private func getBatteryLevel(result: FlutterResult) {
    UIDevice.current.isBatteryMonitoringEnabled = true
    let batteryLevel = Int(UIDevice.current.batteryLevel * 100)
    result(batteryLevel)
  }
}

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Finding Packages/Plugins

Pub.dev (Official Repository)

Visit pub.dev to browse packages.

Quality Indicators:

• ✅ Pub Points (max 160)
• ✅ Popularity score
• ✅ Likes count
• ✅ Verified publishers
• ✅ Null safety support
• ✅ Recent updates

Popular Packages

State Management:

• provider
• riverpod
• flutter_bloc
• get

Networking:

• http
• dio

Local Storage:

• shared_preferences
• hive
• sqflite

UI/UX:

• flutter_svg
• cached_network_image
• shimmer
• lottie

Utils:

• intl
• uuid
• path_provider
• url_launcher

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Creating Your Own Package

Create Package

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flutter create --template=package my_package

Package Structure

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my_package/
├── lib/
│   ├── my_package.dart      # Main export file
│   └── src/
│       └── my_class.dart    # Implementation
├── test/
│   └── my_package_test.dart
├── pubspec.yaml
├── README.md
├── CHANGELOG.md
└── LICENSE

Example Package

lib/my_package.dart:

dartCopy
library my_package;

export 'src/string_utils.dart';

lib/src/string_utils.dart:

dartCopy
class StringUtils {
  static String capitalize(String text) {
    if (text.isEmpty) return text;
    return '${text[0].toUpperCase()}${text.substring(1)}';
  }
  
  static String reverse(String text) {
    return text.split('').reversed.join('');
  }
}

pubspec.yaml:

yamlCopy
name: my_package
description: Useful string utilities
version: 1.0.0
homepage: https://github.com/user/my_package

environment:
  sdk: '>=3.0.0 <4.0.0'

dependencies:
  flutter:
    sdk: flutter

dev_dependencies:
  flutter_test:
    sdk: flutter
  flutter_lints: ^2.0.0

Publish to Pub.dev

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# Dry run
flutter pub publish --dry-run

# Publish
flutter pub publish

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Creating Your Own Plugin

Create Plugin

bashCopy
flutter create --template=plugin my_plugin

Plugin Structure

textCopy
my_plugin/
├── lib/
│   └── my_plugin.dart         # Dart API
├── android/
│   └── src/main/kotlin/       # Android code
├── ios/
│   └── Classes/               # iOS code
├── example/
│   └── lib/main.dart          # Demo app
└── pubspec.yaml

Example Plugin

lib/my_plugin.dart:

dartCopy
import 'package:flutter/services.dart';

class MyPlugin {
  static const MethodChannel _channel = MethodChannel('my_plugin');
  
  static Future<String> getPlatformVersion() async {
    final String version = await _channel.invokeMethod('getPlatformVersion');
    return version;
  }
}

android/src/main/kotlin/MyPlugin.kt:

kotlinCopy
class MyPlugin: FlutterPlugin, MethodCallHandler {
  override fun onMethodCall(call: MethodCall, result: Result) {
    if (call.method == "getPlatformVersion") {
      result.success("Android ${android.os.Build.VERSION.RELEASE}")
    } else {
      result.notImplemented()
    }
  }
}

ios/Classes/MyPlugin.swift:

swiftCopy
public class MyPlugin: NSObject, FlutterPlugin {
  public static func register(with registrar: FlutterPluginRegistrar) {
    let channel = FlutterMethodChannel(name: "my_plugin", binaryMessenger: registrar.messenger())
    let instance = MyPlugin()
    registrar.addMethodCallDelegate(instance, channel: channel)
  }
  
  public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
    if call.method == "getPlatformVersion" {
      result("iOS " + UIDevice.current.systemVersion)
    } else {
      result(FlutterMethodNotImplemented)
    }
  }
}

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Best Practices

Important: Always check package quality before using

✅ Choose Quality Packages

yamlCopy
# Good - High pub points, recent update
dependencies:
  provider: ^6.0.5  # 160/160 points, 1M+ downloads

# Risky - Low quality indicators
dependencies:
  unknown_package: ^0.0.1  # 50/160 points, old version

Version Constraints

yamlCopy
# ✅ Good - Allow compatible updates
dependencies:
  http: ^1.1.0

# ❌ Bad - Locked to exact version
dependencies:
  http: 1.1.0

Minimal Dependencies

yamlCopy
# ✅ Good - Only what you need
dependencies:
  http: ^1.1.0

# ❌ Bad - Unused dependencies
dependencies:
  http: ^1.1.0
  dio: ^5.0.0  # Don't need both!

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Resources

• Pub.dev Package Repository
• Flutter Packages Documentation
• Developing Packages
• Platform Channels