Screen background color android (#465)

* Implement screenBackgroundColor

* Collapse ViewPagerScreen on TopTab select

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

     public int selectedTopTabIndicatorHeight;
     public Color selectedTopTabIndicatorColor;
 
+    public Color screenBackgroundColor;
+
     public boolean drawScreenAboveBottomTabs;
 
     public Color snackbarButtonColor;

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

             result.drawScreenBelowTopBar = false;
         }
 
+        result.screenBackgroundColor = getColor("screenBackgroundColor", getDefaultScreenBackgroundColor());
+
         result.bottomTabsHidden = getBoolean("bottomTabsHidden", getDefaultBottomTabsHidden());
         result.drawScreenAboveBottomTabs = !result.bottomTabsHidden &&
                                            params.getBoolean("drawScreenAboveBottomTabs", getDefaultDrawScreenAboveBottomTabs());
         return AppStyle.appStyle != null && AppStyle.appStyle.drawScreenBelowTopBar;
     }
 
+    private StyleParams.Color getDefaultScreenBackgroundColor() {
+        return AppStyle.appStyle != null ? AppStyle.appStyle.screenBackgroundColor : getColor("screenBackgroundColor", new StyleParams.Color());
+    }
+
     private boolean getDefaultTopTabsHidden() {
         return AppStyle.appStyle != null && AppStyle.appStyle.topTabsHidden;
     }

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

 import android.widget.ScrollView;
 
 import com.reactnativenavigation.events.Event;
+import com.reactnativenavigation.events.ViewPagerScreenChangedEvent;
 import com.reactnativenavigation.events.ViewPagerScreenScrollStartEvent;
 import com.reactnativenavigation.params.PageParams;
 import com.reactnativenavigation.params.ScreenParams;
     @Override
     public void onEvent(Event event) {
         super.onEvent(event);
-        if (ViewPagerScreenScrollStartEvent.TYPE.equals(event.getType())) {
+        if (ViewPagerScreenScrollStartEvent.TYPE.equals(event.getType()) || ViewPagerScreenChangedEvent.TYPE.equals(event.getType())) {
             ((CollapsingView) topBar).collapse(new CollapseAmount(CollapseCalculator.Direction.Down));
             ((CollapsingView) viewPager).collapse(new CollapseAmount(CollapseCalculator.Direction.Down));
         }

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

         setStatusBarColor(styleParams.statusBarColor);
         setNavigationBarColor(styleParams.navigationBarColor);
         topBar.setStyle(styleParams);
+        if (styleParams.screenBackgroundColor.hasColor()) {
+            setBackgroundColor(styleParams.screenBackgroundColor.getColor());
+        }
     }
 
     private void createViews() {

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

 import android.support.v4.view.ViewPager;
 import android.support.v7.app.AppCompatActivity;
 
+import com.reactnativenavigation.events.Event;
+import com.reactnativenavigation.events.ViewPagerScreenChangedEvent;
 import com.reactnativenavigation.params.BaseScreenParams;
 import com.reactnativenavigation.params.PageParams;
 import com.reactnativenavigation.params.ScreenParams;

src/deprecated/platformSpecificDeprecated.android.js

     selectedTopTabIndicatorHeight: originalStyleObject.selectedTopTabIndicatorHeight,
     selectedTopTabIndicatorColor: originalStyleObject.selectedTopTabIndicatorColor,
 
+    screenBackgroundColor: originalStyleObject.screenBackgroundColor,
+
     drawScreenAboveBottomTabs: !originalStyleObject.drawUnderTabBar,
 
     bottomTabsColor: originalStyleObject.tabBarBackgroundColor,