Exposed getUiImplementationProvider for people to override if needed (#3295)

android/app/src/main/java/com/reactnativenavigation/NavigationApplication.java

 import com.facebook.react.ReactNativeHost;
 import com.facebook.react.ReactPackage;
 import com.facebook.react.bridge.ReactContext;
+import com.facebook.react.uimanager.UIImplementationProvider;
 import com.facebook.react.uimanager.UIManagerModule;
 import com.reactnativenavigation.bridge.EventEmitter;
 import com.reactnativenavigation.controllers.ActivityCallbacks;
         super.onCreate();
         instance = this;
         handler = new Handler(getMainLooper());
-        reactGateway = new NavigationReactGateway();
+        reactGateway = new NavigationReactGateway(getUIImplementationProvider());
         eventEmitter = new EventEmitter(reactGateway);
         activityCallbacks = new ActivityCallbacks();
     }
         }
     }
 
+    // here in case someone wants to override this
+    protected UIImplementationProvider getUIImplementationProvider() {
+        return null; // if null the default UIImplementationProvider will be used
+    }
+
     public void startReactContextOnceInBackgroundAndExecuteJS() {
         reactGateway.startReactContextOnceInBackgroundAndExecuteJS();
     }

android/app/src/main/java/com/reactnativenavigation/react/NavigationReactGateway.java

 import com.facebook.react.bridge.ReactContext;
 import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;
 import com.facebook.react.shell.MainReactPackage;
+import com.facebook.react.uimanager.UIImplementationProvider;
 import com.reactnativenavigation.NavigationApplication;
 import com.reactnativenavigation.bridge.NavigationReactEventEmitter;
 import com.reactnativenavigation.bridge.NavigationReactPackage;
 	private JsDevReloadHandler jsDevReloadHandler;
 
 	public NavigationReactGateway() {
-		host = new ReactNativeHostImpl();
+		this(null);
+	}
+
+	public NavigationReactGateway(final UIImplementationProvider customImplProvider) {
+
+		if (customImplProvider != null) {
+			host = new ReactNativeHostImpl() {
+				/**
+				 * This was added in case someone needs to provide a different UIImplementationProvider
+				 * @param {UIImplementationProvider} defaultProvider
+				 * @return {UIImplementationProvider}
+				 */
+				@Override
+				protected UIImplementationProvider getUIImplementationProvider() {
+					return customImplProvider;
+				}
+			};
+		} else {
+			host = new ReactNativeHostImpl();
+		}
+
+
 		jsDevReloadHandler = new JsDevReloadHandler();
 	}
 
 		return host.hasInstance() && getReactInstanceManager().getCurrentReactContext() != null;
 	}
 
+
 	@Override
 	public boolean hasStartedCreatingContext() {
 		return getReactInstanceManager().hasStartedCreatingInitialContext();
 		}
 	}
 
+
 	public ReactNativeHost getReactNativeHost() {
 		return host;
 	}
 		reactEventEmitter = new NavigationReactEventEmitter(context);
 	}
 
-	private static class ReactNativeHostImpl extends ReactNativeHost implements ReactInstanceManager.ReactInstanceEventListener {
+	public static class ReactNativeHostImpl extends ReactNativeHost implements ReactInstanceManager.ReactInstanceEventListener {
 
-		ReactNativeHostImpl() {
+		public ReactNativeHostImpl() {
 			super(NavigationApplication.instance);
 		}
 
+
 		@Override
 		public boolean getUseDeveloperSupport() {
 			return NavigationApplication.instance.isDebug();