izouxv/swift_flutter

A example how to integrate Flutter with existing iOS app (Swift)

This project is a sample of how to add Flutter to existing app. For while is to iOS app only.

It uses "Add-to-App" Flutter feature. We will use Flutter module. This feature is available, while for now (Flutter 1.9), at Flutter master channel, you should run:

$ flutter channel master

iOS

Create a Flutter module

Let's assume you have an existent iOS App at swift_flutter/SwiftFlutter, and that you want you Flutter project as a sibling:

$ flutter create -t module --org com.example flutter_module

This creates a some/path/swift_flutter/SwiftFlutter Flutter module project with some Dart code to get you started and a .android/ hidden sub-folder that wraps up the module project in an Android library. And also, a .ios hidden sub-folder that wraps up the module project that contains some Cocoapods and a helper Ruby script.

Make the host app depend on the Flutter module

The description below assumes that your existing iOS app has a structure similar. If your existing app has a different folder structure and/or existing .xcconfig files, you can reuse those, but probably need to adjust some of the relative paths mentioned below accordingly.

The assumed folder structure is as follows:

some/path/swift_flutter
  flutter_module/
    lib/main.dart
    .ios/
    ...
  SwiftFlutter/
    SwiftFlutter/
      AppDelegate.swift
      ...

Add your Flutter app to your Podfile

Integrating the Flutter framework requires use of the CocoaPods dependency manager. This is because the Flutter framework needs to be available also to any Flutter plugins that you might include in flutter_module.

Add the following lines to your Podfile:

flutter_application_path = 'path/to/flutter_module/'
load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')

For each XCode target that needs to embed Flutter, call install_all_flutter_pods(flutter_application_path).

target 'SwiftFlutter' do
    install_all_flutter_pods(flutter_application_path)
end
target 'SwiftFlutterTests' do
    install_all_flutter_pods(flutter_application_path)
end

Whenever you change the Flutter plugin dependencies in some/path/flutter_module/pubspec.yaml, you need to run flutter packages get from some/path/flutter_module to refresh the list of plugins read by the podhelper.rb script. Then run pod install again from some/path/SwiftFlutter.

The podhelper.rb script will ensure that your plugins, the Flutter.framework, and the App.framework are embedded in your project.

You should now be able to build the project using ⌘B.

Write code to use FlutterViewController from your host app

The proper place to do this will be specific to your host app. Here is an example that makes sense for the blank screen of the host app generated by XCode 10.0.

First declare your app delegate to be a subclass of FlutterAppDelegate. Then define a FlutterEngine property, which help you to register a plugin without a FlutterViewController instance.

In your AppDelegate.swift:

import UIKit
import Flutter
import FlutterPluginRegistrant // Only if you have Flutter Plugins.

@UIApplicationMain
class AppDelegate: FlutterAppDelegate {
  var flutterEngine : FlutterEngine?;
  // Only if you have Flutter plugins.
  override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    self.flutterEngine = FlutterEngine(name: "io.flutter", project: nil);
    self.flutterEngine?.run(withEntrypoint: nil);
    GeneratedPluginRegistrant.register(with: self.flutterEngine);

    return super.application(application, didFinishLaunchingWithOptions: launchOptions);
  }
}

In your ViewController.swift:

import UIKit
import Flutter

class ViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()

    let button = UIButton(type:UIButton.ButtonType.custom)
    button.addTarget(self, action: #selector(handleButtonAction), for: .touchUpInside)
    button.setTitle("Press me", for: UIControl.State.normal)
    button.frame = CGRect(x: 80.0, y: 210.0, width: 160.0, height: 40.0)
    button.backgroundColor = UIColor.blue

    self.view.addSubview(button)
  }

  @objc func handleButtonAction() {
    let flutterEngine = (UIApplication.shared.delegate as? AppDelegate)?.flutterEngine;
    let flutterViewController = FlutterViewController(engine: flutterEngine, nibName: nil, bundle: nil)!;

    self.present(flutterViewController, animated: false, completion: nil)
  }
}

You should now be able to build and launch SwiftFlutter on the Simulator or on a device. Pressing the button should bring up a full-screen Flutter view with the standard Flutter Demo counting app.