force portrait mode for now

android/app/src/main/AndroidManifest.xml

     package="com.reactnativenavigation">
 
     <application>
-        <activity android:name=".controllers.NavigationActivity" />
+        <activity
+            android:name=".controllers.NavigationActivity"
+            android:screenOrientation="portrait" />
     </application>
 
 </manifest>