Create a Custom Flutter Plugin with Android Support (Full Integration Guide)

import 'package:flutter/services.dart';

class FlutterCustomPlugin {
  static const MethodChannel _channel = MethodChannel('flutter_custom_plugin');

  static Future<String?> getPlatformVersion() async {
    final String? version = await _channel.invokeMethod('getPlatformVersion');
    return version;
  }
}

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📱 Step 4: Implement Android Platform Code

android/src/main/java/com/example/flutter_custom_plugin/FlutterCustomPlugin.java

package com.example.flutter_custom_plugin;

import androidx.annotation.NonNull;
import io.flutter.embedding.engine.plugins.FlutterPlugin;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;

public class FlutterCustomPlugin implements FlutterPlugin, MethodChannel.MethodCallHandler {
  private MethodChannel channel;

  @Override
  public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
    channel = new MethodChannel(binding.getBinaryMessenger(), "flutter_custom_plugin");
    channel.setMethodCallHandler(this);
  }

  @Override
  public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
    if (call.method.equals("getPlatformVersion")) {
      result.success("Android " + android.os.Build.VERSION.RELEASE);
    } else {
      result.notImplemented();
    }
  }

  @Override
  public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
    channel.setMethodCallHandler(null);
  }
}

Explanation:
This Java class implements FlutterPlugin and MethodCallHandler. When getPlatformVersion is invoked from Dart, it returns the current Android OS version. If the method isn’t recognized, notImplemented() is called.

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🧪 Step 5: Use the Plugin in a Flutter App

1. Add the plugin to your pubspec.yaml:

dependencies:
  flutter_custom_plugin:
    path: ../flutter_custom_plugin

2. Call it in your main app:

import 'package:flutter/material.dart';
import 'package:flutter_custom_plugin/flutter_custom_plugin.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: PluginHome(),
    );
  }
}

class PluginHome extends StatefulWidget {
  @override
  _PluginHomeState createState() => _PluginHomeState();
}

class _PluginHomeState extends State<PluginHome> {
  String _platformVersion = 'Unknown';

  @override
  void initState() {
    super.initState();
    getPlatformVersion();
  }

  Future<void> getPlatformVersion() async {
    final version = await FlutterCustomPlugin.getPlatformVersion();
    setState(() {
      _platformVersion = version ?? 'Failed to get version';
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Flutter Plugin Example")),
      body: Center(child: Text('Running on: $_platformVersion')),
    );
  }
}

Explanation:
We call our plugin’s getPlatformVersion() function inside initState() and display the Android OS version using a Text widget.

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🔄 Testing the Plugin

• Run the example app using flutter run.
• You should see the OS version returned from native Android code.
• If using Kotlin, ensure your plugin class uses override fun in a similar structure.

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🧠 Final Thoughts

Creating a custom Flutter plugin with Android support allows you to: