I was setup UIImplementationProvider in ReactNativeHost, and do the fresco initialization as well.but when start the application it would report an error because add the RootView in non-UIThread.

@Override
        protected UIImplementationProvider getUIImplementationProvider() {
            Fresco.initialize(getApplicationContext());
            return new FlatUIImplementationProvider();
        }

Environment:
OS: macOS Sierra 10.12.6
Node: 9.2.0
Yarn: 1.3.2
npm: 5.5.1
Watchman: 4.9.0
Android Studio 3.0.1 Build #AI-171.4443003, built on November 10, 2017

Packages: (wanted => installed)
react-native: 0.50.1 => 0.50.1
react: 16.0.0-alpha.12 => 16.0.0

Target Platform: Android 6.0 and 7.0
--------stacktrace-------

mqt_native_modules(2027)

android.view.ViewRootImpl$CalledFromWrongThreadException
Only the original thread that created a view hierarchy can touch its views.
android.view.ViewRootImpl.checkThread(ViewRootImpl.java:7318)

2 android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:1078)
3 android.view.View.requestLayout(View.java:19062)
4 android.view.View.requestLayout(View.java:19062)
5 android.view.View.requestLayout(View.java:19062)
6 android.view.View.requestLayout(View.java:19062)
7 android.widget.RelativeLayout.requestLayout(RelativeLayout.java:381)
8 android.view.View.requestLayout(View.java:19062)
9 android.view.ViewGroup.addView(ViewGroup.java:4272)
10 android.view.ViewGroup.addView(ViewGroup.java:4215)
11 android.view.ViewGroup.addView(ViewGroup.java:4188)
12 com.facebook.react.flat.FlatNativeViewHierarchyManager.addRootView(FlatNativeViewHierarchyManager.java:51)
13 com.facebook.react.uimanager.UIViewOperationQueue.addRootView(UIViewOperationQueue.java:605)
14 com.facebook.react.uimanager.UIImplementation.registerRootView(UIImplementation.java:203)
15 com.facebook.react.uimanager.UIManagerModule.addRootView(UIManagerModule.java:308)
16 com.facebook.react.ReactInstanceManager.attachRootViewToInstance(ReactInstanceManager.java:1032)
17 com.facebook.react.ReactInstanceManager.setupReactContext(ReactInstanceManager.java:980)
18 com.facebook.react.ReactInstanceManager.access$1200(ReactInstanceManager.java:112)
19 com.facebook.react.ReactInstanceManager$4$2.run(ReactInstanceManager.java:943)
20 android.os.Handler.handleCallback(Handler.java:815)
21 android.os.Handler.dispatchMessage(Handler.java:104)
22 com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31)

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