fixes

android/app/src/main/java/com/reactnativenavigation/params/ScreenStyleParams.java

 
     public Color navigationBarColor;
 
-    public boolean drawUnderTopBar;
+    public boolean drawBelowTopBar;
 }

android/app/src/main/java/com/reactnativenavigation/params/parsers/ScreenStyleParamsParser.java

                 new ScreenStyleParams.Color(ColorParser.parse(params.getString("bottomTabsButtonColor")));
         result.selectedBottomTabsButtonColor =
                 new ScreenStyleParams.Color(ColorParser.parse(params.getString("selectedBottomTabsButtonColor")));
-        result.drawUnderTopBar = params.getBoolean("drawUnderTopBar", false);
+        result.drawBelowTopBar = params.getBoolean("drawBelowTopBar", false);
         return result;
     }
 }

android/app/src/main/java/com/reactnativenavigation/screens/FragmentScreen.java

 import android.app.FragmentManager;
 import android.app.FragmentTransaction;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.support.v7.app.AppCompatActivity;
 import android.widget.FrameLayout;
     protected void createContent() {
         content = new FrameLayout(getContext());
         content.setId(ViewUtils.generateViewId());
-        ContentView contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, null);
-        addView(contentView, 0, 0);
-        addView(content, addBelowTopBar());
+        addContent();
         addFragment();
-        contentView.init();
     }
 
-    @NonNull
-    private LayoutParams addBelowTopBar() {
+    private void addContent() {
+        ContentView contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, null);
+        addView(contentView, 0, 0);
         LayoutParams params = new LayoutParams(MATCH_PARENT, MATCH_PARENT);
-        if (!screenParams.styleParams.drawUnderTopBar) {
+        if (screenParams.styleParams.drawBelowTopBar) {
             params.addRule(BELOW, topBar.getId());
         }
-        return params;
+        addView(content, params);
     }
 
 

android/app/src/main/java/com/reactnativenavigation/screens/ScreenFactory.java

         if (screenParams.isFragmentScreen()) {
             return new FragmentScreen(activity, screenParams, titleBarBackButtonListener);
         } else if (screenParams.hasTopTabs()) {
-            return new TabbedScreen(activity, screenParams, titleBarBackButtonListener);
+            return new ViewPagerScreen(activity, screenParams, titleBarBackButtonListener);
         } else {
             return new SingleScreen(activity, screenParams, titleBarBackButtonListener);
         }

android/app/src/main/java/com/reactnativenavigation/screens/SingleScreen.java

 package com.reactnativenavigation.screens;
 
-import android.support.annotation.NonNull;
 import android.support.v7.app.AppCompatActivity;
 
 import com.reactnativenavigation.params.ScreenParams;
     @Override
     protected void createContent() {
         contentView = new ContentView(getContext(), screenParams.screenId, screenParams.passProps, screenParams.navigationParams, this);
-        addView(contentView, addBelowTopBar());
-        contentView.init();
-    }
-
-    @NonNull
-    private LayoutParams addBelowTopBar() {
         LayoutParams params = new LayoutParams(MATCH_PARENT, MATCH_PARENT);
-        if (!screenParams.styleParams.drawUnderTopBar) {
+        if (screenParams.styleParams.drawBelowTopBar) {
             params.addRule(BELOW, topBar.getId());
         }
-        return params;
+        addView(contentView, params);
     }
 
     @Override

android/app/src/main/java/com/reactnativenavigation/screens/TabbedScreen.java → android/app/src/main/java/com/reactnativenavigation/screens/ViewPagerScreen.java

 package com.reactnativenavigation.screens;
 
-import android.support.annotation.NonNull;
 import android.support.design.widget.TabLayout;
 import android.support.v4.view.PagerAdapter;
 import android.support.v4.view.ViewPager;
 
 import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
 
-public class TabbedScreen extends Screen {
+public class ViewPagerScreen extends Screen {
 
     private List<ContentView> contentViews;
     private ViewPager viewPager;
     private ContentViewPagerAdapter adapter;
 
-    public TabbedScreen(AppCompatActivity activity, ScreenParams screenParams, TitleBarBackButtonListener backButtonListener) {
+    public ViewPagerScreen(AppCompatActivity activity, ScreenParams screenParams, TitleBarBackButtonListener backButtonListener) {
         super(activity, screenParams, backButtonListener);
     }
 
                     screenParams.passProps,
                     screenParams.navigationParams,
                     this);
-            viewPager.addView(contentView, addBelowTopBar());
-            contentView.init();
+            addContent(contentView);
             contentViews.add(contentView);
         }
 
         tabLayout.setupWithViewPager(viewPager);
     }
 
-    @NonNull
-    private LayoutParams addBelowTopBar() {
+    private void addContent(ContentView contentView) {
         LayoutParams params = new LayoutParams(MATCH_PARENT, MATCH_PARENT);
-        if (!screenParams.styleParams.drawUnderTopBar) {
+        if (screenParams.styleParams.drawBelowTopBar) {
             params.addRule(BELOW, topBar.getId());
         }
-        return params;
+        viewPager.addView(contentView, params);
     }
 
     @Override

android/app/src/main/java/com/reactnativenavigation/views/ContentView.java

         this.screenId = screenId;
         this.passProps = passProps;
         this.navigationParams = navigationParams;
-        scrollViewAttacher = new ScrollViewAttacher(scrollListener);
+        if (scrollListener != null) {
+            scrollViewAttacher = new ScrollViewAttacher(scrollListener);
+        }
+        attachToJS();
     }
 
-    public void init() {
+    private void attachToJS() {
         ReactInstanceManager react = NavigationApplication.instance.getNavigationReactInstance().getReactInstanceManager();
         startReactApplication(react, screenId, mergePropsAndNavigationParams());
     }
     @Override
     public void onViewAdded(View child) {
         super.onViewAdded(child);
-        scrollViewAttacher.onViewAdded(child);
+        if (scrollViewAttacher != null) {
+            scrollViewAttacher.onViewAdded(child);
+        }
     }
 
     private Bundle mergePropsAndNavigationParams() {