flutter-plugins

flutter-plugin-generator

Goal

Scaffolds and configures Flutter plugin packages, handling standard method channels, FFI integrations, and federated plugin architectures. It configures platform-specific native code environments, implements Android v2 embedding lifecycle interfaces, and establishes platform interface packages.

Decision Logic

Use the following decision tree to determine the plugin architecture and template:

1. Does the plugin require C/C++ native code via dart:ffi?

• Yes: Use --template=plugin_ffi.
• Note: FFI plugins support bundling native code and method channel registration, but not method channels themselves.
• No: Proceed to step 2.

1. Does the plugin require BOTH dart:ffi and Method Channels?

• Yes: Use --template=plugin (Non-FFI). You must configure FFI manually within the standard plugin structure.
• No: Proceed to step 3.

1. Will the plugin be developed by multiple teams or require highly decoupled platform implementations?

• Yes: Implement a Package-Separated Federated Plugin (App-facing package, Platform Interface package, Platform Implementation packages).
• No: Implement a standard monolithic plugin.

Instructions

1. Gather Plugin Requirements

STOP AND ASK THE USER:

• What is the plugin name?
• What is the organization name (reverse domain notation, e.g., com.example)?
• Which platforms should be supported (comma-separated: android,ios,web,linux,macos,windows)?
• Do you need an FFI plugin or a standard Method Channel plugin?
• Do you prefer Java or Kotlin for Android? Objective-C or Swift for iOS?
• Should this be a federated plugin?

1. Generate the Plugin Package

Execute the Flutter CLI command based on the user's parameters.

Standard Plugin Example:

   flutter create --org com.example --template=plugin --platforms=android,ios,macos -a kotlin -i swift my_plugin

FFI Plugin Example:

   flutter create --template=plugin_ffi my_ffi_plugin

1. Configure Federated Plugin Architecture (If Applicable)

If the user requested a federated plugin, configure the pubspec.yaml of the app-facing package to endorse the platform implementations.

   # App-facing pubspec.yaml
   flutter:
     plugin:
       platforms:
         android:
           default_package: my_plugin_android
         windows:
           default_package: my_plugin_windows

   dependencies:
     my_plugin_android: ^1.0.0
     my_plugin_windows: ^1.0.0

For the platform implementation packages, define the implements key:

   # Platform implementation pubspec.yaml (e.g., my_plugin_windows)
   flutter:
     plugin:
       implements: my_plugin
       platforms:
         windows:
           pluginClass: MyPlugin

1. Prepare Native Environments for Editing

Before modifying native code, you MUST build the example app to resolve dependencies and generate necessary files.

   cd my_plugin/example
   flutter build apk --config-only # For Android
   flutter build ios --no-codesign --config-only # For iOS
   flutter build windows # For Windows

1. Implement Android v2 Embedding Lifecycle

Modify the Android plugin class (e.g., android/src/main/kotlin/com/example/my_plugin/MyPlugin.kt). Extract logic from registerWith() into a private method shared with onAttachedToEngine(). Implement ActivityAware or ServiceAware if context is needed.

   package com.example.my_plugin

   import androidx.annotation.NonNull
   import io.flutter.embedding.engine.plugins.FlutterPlugin
   import io.flutter.embedding.engine.plugins.activity.ActivityAware
   import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
   import io.flutter.plugin.common.MethodCall
   import io.flutter.plugin.common.MethodChannel
   import io.flutter.plugin.common.MethodChannel.MethodCallHandler
   import io.flutter.plugin.common.MethodChannel.Result

   class MyPlugin: FlutterPlugin, MethodCallHandler, ActivityAware {
     private lateinit var channel : MethodChannel

     override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
       setupChannel(flutterPluginBinding.binaryMessenger)
     }

     // Shared private method for v1 and v2 embedding compatibility
     private fun setupChannel(messenger: BinaryMessenger) {
       channel = MethodChannel(messenger, "my_plugin")
       channel.setMethodCallHandler(this)
     }

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

     override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
       channel.setMethodCallHandler(null)
     }

     override fun onAttachedToActivity(binding: ActivityPluginBinding) {
       // Handle Activity attachment
     }

     override fun onDetachedFromActivityForConfigChanges() {}
     override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {}
     override fun onDetachedFromActivity() {}
   }

1. Validate and Fix

Run the plugin tests and analyzer to ensure the generated code is valid.

   cd my_plugin
   flutter analyze
   flutter test

If the analyzer reports missing dependencies or unresolved native symbols, verify that step 4 (building the example app) was executed successfully. Fix any missing imports in the native code blocks.

Constraints

• Never attempt to use Method Channels inside a package created with --template=plugin_ffi. If both are required, use --template=plugin.
• Always build the example project (flutter build <platform>) at least once before attempting to edit or analyze native Android (build.gradle), iOS (.xcworkspace), or Windows (.sln) files.
• Never leave public members undocumented in the Dart API (lib/<package_name>.dart).
• Always use the v2 Android embedding (FlutterPlugin). Do not rely solely on the deprecated PluginRegistry.Registrar.
• Never edit the .android or .ios directories inside a Flutter module; only edit the native code inside the plugin's android/ or ios/ directories.