An example demostrates how to add a new Flutter sub-module into existing native Android and iOS project, to make the drastic transition smoother.

A detailed step-by-step guide on how to setup a Flutter hybrid project is available here:

1. Power of hybrid (I): add flutter to existing apps
2. Power of hybrid (II): communicate with native code

Below is a quick-start guide to get things running.

Import Flutter project

Install Flutter SDK if you haven't already. This example uses v1.9.1.

1. Go to folder FlutterHybridExample/flutter_common_module, type command line to generate common binary files:

flutter pub get

2. Open Android Studio, import this project by clicking File -> Open, open folder FlutterHybridExample/flutter_common_module.

Then you should be able to build and run a demo pure Flutter app on your Android or iOS devices.

Import iOS project

Install cocoapods if you haven't already.

1. Go to folder FlutterHybridExample/ios_native_app, type command line to install cocoapods dependencies:

pod install

2. Open the project by command line:

open ios_native_app.xcworkspace

Then you should be able to run the app with Flutter module embedded.

Build error

With Flutter 1.9.1 you might run into this build error in the final phase [CP] Embed Pods Frameworks, saying permission denied when signing file Flutter.framework:

PhaseScriptExecution [CP] Embed Pods Frameworks

/Users/myuser/Library/Developer/Xcode/DerivedData/ios_native_app/Build/Products/Debug-iphonesimulator/ios_native_app.app/Frameworks/Flutter.framework: replacing existing signature
/Users/myuser/Library/Developer/Xcode/DerivedData/ios_native_app/Build/Products/Debug-iphonesimulator/ios_native_app.app/Frameworks/Flutter.framework: Permission denied
Command PhaseScriptExecution failed with a nonzero exit code

According to a user replied in Flutter issue tracker, it can be fixed by adding a line chmod -R +w $1 to script ios_native_app/Pods/Target Support Files/Pods-ios_native_app/Pods-ios_native_app-frameworks.sh.

code_sign_if_enabled() {
  if [ -n "${EXPANDED_CODE_SIGN_IDENTITY:-}" -a "${CODE_SIGNING_REQUIRED:-}" != "NO" -a "${CODE_SIGNING_ALLOWED}" != "NO" ]; then
    # Use the current code_sign_identity
    echo "Code Signing $1 with Identity ${EXPANDED_CODE_SIGN_IDENTITY_NAME}"
    chmod -R +w $1 # ADD THIS NEW LINE
    local code_sign_cmd="/usr/bin/codesign --force --sign ${EXPANDED_CODE_SIGN_IDENTITY} ${OTHER_CODE_SIGN_FLAGS:-} --preserve-metadata=identifier,entitlements '$1'"

    if [ "${COCOAPODS_PARALLEL_CODE_SIGN}" == "true" ]; then
      code_sign_cmd="$code_sign_cmd &"
    fi
    echo "$code_sign_cmd"
    eval "$code_sign_cmd"
  fi
}

Import Android project

1. Open Android Studio, import this project by clicking File -> Open, open folder FlutterHybridExample/android_native_app.

After a minute of gradle sync, you should be able to run the app with Flutter module embedded.