瞭解了Flutter的Widget以及Flutter的渲染，突然有新的問題的產生，Flutter如果要和Native進行混合開發，就會產生新的問題，

• 混合棧管理

比如Flutter要回退到原生介面，原生介面應該如何感知呢，原生介面進入Flutter介面又要怎麼通知Native

根據原始碼加圖片來看下Flutter怎麼在Android啟動

Flutter出現的目的旨在統一Android/IOS兩端程式設計，因此完全基於Flutter開發的App，只需提供一個包含FlutterView的頁面，後續頁面增加/刪除/跳轉均在FlutterView的Navigator中進行管理。

直接公佈最合適的方案

抽取單一FlutterView或FlutterNativeView，後續每啟動一個Activity都對FlutterView或FlutterNativeView進行復用

對比RN，native與rn混合開發，是有一個reactActivity，用layoutInspector看下Flutter層面

可以看到flutter基於自身去渲染

接下來用原始碼看戲FlutterActivity都做了什麼操作

public class FlutterActivity extends Activity implements Provider, PluginRegistry, ViewFactory {
    private final FlutterActivityDelegate delegate = new FlutterActivityDelegate(this, this);//1
    private final FlutterActivityEvents eventDelegate;//1
    private final Provider viewProvider;
    private final PluginRegistry pluginRegistry;//2

    public FlutterActivity() {
        this.eventDelegate = this.delegate;
        this.viewProvider = this.delegate;
        this.pluginRegistry = this.delegate;
    }
    …………
}
 

看下建構函式   

  2.pluginRegistry主要用於原生方法註冊通訊的，封裝一些方法，相當於給Flutter增加外掛

1.FlutterActivityEvents是一個介面，具體實現類是FlutterActivityDelegate 給FlutterView傳送當前app處於的狀態，包括記憶體和生命週期，上下文，以及intent

   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.eventDelegate.onCreate(savedInstanceState);
    }
  public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        this.eventDelegate.onConfigurationChanged(newConfig);
    }

  protected void onPostResume() {
        super.onPostResume();
        this.eventDelegate.onPostResume();
    }
…………
 

1.我們知道當走到Activity的onCreate時，會執行Delegate的onCreate

    public FlutterActivityDelegate(Activity activity, FlutterActivityDelegate.ViewFactory viewFactory) {
        this.activity = (Activity)Preconditions.checkNotNull(activity);
        this.viewFactory = (FlutterActivityDelegate.ViewFactory)Preconditions.checkNotNull(viewFactory);
    }

這裡面接受一個Activity

    public void onCreate(Bundle savedInstanceState) {
        if (VERSION.SDK_INT >= 21) {
            Window window = this.activity.getWindow();
            window.addFlags(-2147483648);
            window.setStatusBarColor(1073741824);
            window.getDecorView().setSystemUiVisibility(1280);
        }

        String[] args = getArgsFromIntent(this.activity.getIntent());
        FlutterMain.ensureInitializationComplete(this.activity.getApplicationContext(), args);
        this.flutterView = this.viewFactory.createFlutterView(this.activity);
        if (this.flutterView == null) {
            FlutterNativeView nativeView = this.viewFactory.createFlutterNativeView();
            this.flutterView = new FlutterView(this.activity, (AttributeSet)null, nativeView);
            this.flutterView.setLayoutParams(matchParent);
            this.activity.setContentView(this.flutterView);
            this.launchView = this.createLaunchView();
            if (this.launchView != null) {
                this.addLaunchView();
            }
        }

        if (!this.loadIntent(this.activity.getIntent())) {
            if (!this.flutterView.getFlutterNativeView().isApplicationRunning()) {
                String appBundlePath = FlutterMain.findAppBundlePath(this.activity.getApplicationContext());
                if (appBundlePath != null) {
                    FlutterRunArguments arguments = new FlutterRunArguments();
                    arguments.bundlePath = appBundlePath;
                    arguments.entrypoint = "main";
                    this.flutterView.runFromBundle(arguments);
                }
            }

        }
    }