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.
2. 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.
3. 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?

2. 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
   

3. 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
   

4. 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
   

5. 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() {}
   }
   

6. 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.