在上一篇文章Flutter(六)：Flutter_Boost接入現有原生工程(iOS+Android)中介紹了Flutter_Boost的接入方法，這一篇將介紹Flutter自帶的接入方法。

新建工程

1.新建工程

• 1.使用Xcode新建flutter_demo_ios（模擬已有工程）
• 2.使用AndroidStudio新建flutter_demo_android（模擬已有工程）
• 3.使用AndroidStudio新建flutter_demo_flutter（新的flutter庫工程）

備註：
1.AndroidSudio需要安裝Dart和Flutter插件
2.flutter工程新建時選擇Module

2.新建完成

目錄結構如下：

Android接入

1.setting.gradle新增

setBinding(new Binding([gradle: this]))                             
evaluate(new File(                                                  
        settingsDir.parentFile,                                            
        'flutter_demo_library/.android/include_flutter.groovy'                        
))                

2.app下的build.gradle增加依賴

implementation project(':flutter')

然後執行gradle sync

3.跳轉代碼

startActivity(FlutterActivity.createDefaultIntent(currentActivity))

iOS接入

1.修改pod文件

flutter_application_path = '../flutter_demo_library'
load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')

target 'flutter_demo_ios' do
  # Comment the next line if you don't want to use dynamic frameworks
  use_frameworks!

  # Pods for flutter_demo_ios
  install_all_flutter_pods(flutter_application_path)
  
end

post_install do |installer|
  flutter_post_install(installer) if defined?(flutter_post_install)
end

執行pod install，podhelper.rb 腳本會把你的 plugins， Flutter.framework，和 App.framework 集成到你的項目中。

2.修改ViewController中的跳轉代碼

let flutterEngine = (UIApplication.shared.delegate as! AppDelegate).flutterEngine
let flutterViewController = FlutterViewController(engine: flutterEngine, nibName: nil, bundle: nil)
self.navigationController?.pushViewController(flutterViewController, animated: true)

ViewController記得還需要import Flutter，至此iOS接入完畢，使用模擬器也可以正常執行。

問題集錦

Android

1、Caused by: org.gradle.api.InvalidUserCodeException: Build was configured to prefer settings repositories over project repositories but repository 'maven' was added by plugin class 'FlutterPlugin'

原因：Android項目和Flutter項目的Gradle配置不一樣
解決方案：
1、只是demo的話，把Flutter/.android/根目錄下的setting.gradle和build.gradl拷貝到Android/根目錄下，替換Android項目自帶的
2、如果是老的工程，可以參考Flutter 混合開發組件化與工程化架構

2.解決Flutter 交互頁面可見之前會有一個短暫的延遲

原因：每一個 FlutterActivity 預設會創建它自己的 FlutterEngine。每一個 FlutterEngine 會有一個明顯的預熱時間。這意味著載入一個標準的 FlutterActivity 時，在你的 Flutter 交互頁面可見之前會有一個短暫的延遲。

解決方案：想要最小化這個延遲時間，你可以在抵達你的 FlutterActivity 之前，初始化一個 FlutterEngine，然後使用這個已經預熱好的 FlutterEngine。

在Application加入代碼:

class MyApplication : Application() {
  lateinit var flutterEngine : FlutterEngine

  override fun onCreate() {
    super.onCreate()

    // Instantiate a FlutterEngine.
    flutterEngine = FlutterEngine(this)

    // Start executing Dart code to pre-warm the FlutterEngine.
    flutterEngine.dartExecutor.executeDartEntrypoint(
      DartExecutor.DartEntrypoint.createDefault()
    )

    // Cache the FlutterEngine to be used by FlutterActivity.
    FlutterEngineCache
      .getInstance()
      .put("my_engine_id", flutterEngine)
  }
}

跳轉代碼：

startActivity(FlutterActivity
      .withCachedEngine("my_engine_id")
      .build(this))