The Klutter Framework makes it possible to write a Flutter plugin for both Android and iOS using Kotlin Multiplatform. Instead of writing platform specific code twice in 2 languages (Swift + Kotlin), it can be written once in Kotlin and used as a Flutter plugin.

Features

Use this plugin if you want to:

Write platform-specific code only once for both Android and IOS in Kotlin.
Use Kotlin Multiplatform libraries in your Flutter app.
Depend on other plugins made with Klutter.
Auto-generate Dart code for your (native) Platform library.

Getting started

Installation
Using plugins
Creating plugins
FAQ!

Easiest way to start a new project is with the Intellij or Android Studio plugin. This plugin will create a new Flutter plugin and setup Klutter automatically.
For a step-by-step guide (doing everything manually), see the battery app with Klutter tutorial.

Installation

What's the point?
Plugins build with the Klutter Framework work slightly different from regular plugins. The Klutter dependency is a requirement for both using and creating plugins with Klutter.

Steps:
Add the Klutter library to dependencies in the pubspec.yaml:

dev_dependencies:  
 klutter: ^0.3.0

Then run:

flutter pub get

Usage

What's the point?
Plugins build with the Klutter Framework work slightly different from regular plugins. The following tasks help Flutter to locate Klutter plugins and ensure compatibility between Flutter Android/IOS configuration and Klutter plugin Android/IOS configuration.

Steps:

Installation.
Initialization.
Add dependencies.

Install Klutter as dependency as described here.

Initialize Klutter in your project by running:

flutter pub run klutter:consumer init

The init task will set up Klutter for both Android and iOS. Alternatively you can set up Android and IOS separately.

Setup Android by running:

flutter pub run klutter:consumer init=android

Setup IOS by running:

flutter pub run klutter:consumer init=ios

Finally, Klutter plugins can be added by running the add command.

Example:
Add the library 'awesome_plugin' to your project:

flutter pub run klutter:consumer add=awesome_plugin

Background
The consumer init task will configure your Flutter project in:

IOS
Android

IOS
The Podfile has to be editted to be able to run the app on an iPhone simulator. Klutter will look for the following code block in the Podfile:

 post_install do |installer|
   installer.pods_project.targets.each do |target|
     flutter_additional_ios_build_settings(target)
   end
 end

Then it will be updated to the following code:

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_ios_build_settings(target)
    target.build_configurations.each do |bc|
        bc.build_settings['ARCHS[sdk=iphonesimulator*]'] =  `uname -m`
     end
  end
end

Android
The consumer init task will do the following for Android in your Flutter project:

Create a .klutter-plugins file in the root folder.
Create a new Gradle file in the flutter/packages/flutter_tools/gradle.
Update the android/settings.gradle file to apply the newly generated Gradle file.
Update the min/compile/target SDK versions to 21/31/31 in the android/app/build.gradle file.

The .klutter-plugins file will register all Klutter made plugins used in your project. The created Gradle file in the flutter_tools manages the plugins and enables them to be found by the Flutter project.

The task klutter:add registers a Klutter plugin in the .klutter-plugins file. This is then used by the Android Gradle file to find the plugin location and add the generated artifacts to your build.

Creation

What's the point?
The starting point of a Klutter plugins is a regular Flutter plugin project. The following steps describe how to create a Flutter plugin project and initialize Klutter in it.

Steps:

Create Flutter plugin project.
Installation.
Initialization.
Build Platform module and generate Dart code.
Verify your plugin.

Run the following to create a new Flutter plugin, substituting 'org.example' with your organisation name and 'plugin_name' with your plugin name:

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

Install the Klutter Framework as dependency and then run:

flutter pub run klutter:producer init

Build the platform module by running the following in the root folder (takes a few minutes!):

./gradlew clean build -p "platform"

Now test the plugin by following the steps outlined here in the root/example project. When done you can run the example project from the root/example/lib folder and see your first plugin in action!

Faq!

App won't start on...

App won't start

Make sure you have followed all the following steps:

flutter create <your_plugin_name> --org <your_organisation> --template=plugin --platforms=android,ios -a kotlin -i swift.
klutter is added to the dependencies in your pubspec.yaml (both the plugin and plugin/example for testing).
do flutter pub get in both root and root/example folder.
do flutter pub run klutter:producer init in the root folder.
do ./gradlew clean build -p "platform" in the root folder.
do flutter pub run klutter:consumer init in the root/example folder.
do flutter pub run klutter:consumer add=<your_plugin_name> in the root/example folder.

For Android emulator:

There should be a .klutter-plugins file in the root/example folder containing an entry for your plugin. If not then do flutter pub run klutter:consumer add=<your_plugin_name> in the root/example folder again.

There should be a platform.aar file in the root/android/klutter folder. If not then do ./gradlew clean build -p "platform" from the root folder.

For iOS simulator:

There should be a Platform.xcframework folder in root/ios/Klutter. If not then do ./gradlew clean build -p "platform" from the root folder.

If there's an error message saying unable to find plugin or similar then run pod update (or for Mac M1 users you might have to do: arch -x86_64 pod install) in the root/example/ios folder.