Implement TopBar.elevation option

This commit also changes the way TopBar background color is applied.
Instead of applying it to the TitleBar, it's applied to the entire TopBar layout

docs/docs/styling.md

     backgroundColor: 'red'
   },
   topBar: {
-    height: 70, // TopBar height in dp.
+    height: 70, // TopBar height in dp
     borderColor: 'red',
     borderHeight: 1.3,
+    elevation: 1.5, // TopBar elevation in dp
     title: {
-      height: 70 // TitleBar height in dp.
+      height: 70 // TitleBar height in dp
     }
   },
   bottomTabs: {

lib/android/app/src/main/java/com/reactnativenavigation/parse/TopBarOptions.java

         options.height = NumberParser.parse(json, "height");
         options.borderColor = ColorParser.parse(json, "borderColor");
         options.borderHeight = FractionParser.parse(json, "borderHeight");
+        options.elevation = FractionParser.parse(json, "elevation");
 
         options.validate();
         return options;
     public Bool hideOnScroll = new NullBool();
     public Bool drawBehind = new NullBool();
     public Number height = new NullNumber();
+    public Fraction elevation = new NullFraction();
     public Fraction borderHeight = new NullFraction();
     public Color borderColor = new NullColor();
     @Nullable public ArrayList<Button> leftButtons;
         if (other.height.hasValue()) height = other.height;
         if (other.borderHeight.hasValue()) borderHeight = other.borderHeight;
         if (other.borderColor.hasValue()) borderColor = other.borderColor;
+        if (other.elevation.hasValue()) elevation = other.elevation;
         validate();
     }
 
         if (!height.hasValue()) height = defaultOptions.height;
         if (!borderHeight.hasValue()) borderHeight = defaultOptions.borderHeight;
         if (!borderColor.hasValue()) borderColor = defaultOptions.borderColor;
+        if (!elevation.hasValue()) elevation = defaultOptions.elevation;
         validate();
     }
 

lib/android/app/src/main/java/com/reactnativenavigation/presentation/StackOptionsPresenter.java

 
     private void applyTopBarOptions(TopBarOptions options, AnimationsOptions animationOptions, Component component, Options componentOptions) {
         topBar.setHeight(options.height.get(LayoutParams.WRAP_CONTENT));
+        topBar.setElevation(options.elevation);
 
         topBar.setTitleHeight(options.title.height.get(LayoutParams.WRAP_CONTENT));
         topBar.setTitle(options.title.text.get(""));
     }
 
     private void mergeTopBarOptions(TopBarOptions options, AnimationsOptions animationsOptions, Component component) {
+        if (options.height.hasValue()) topBar.setHeight(options.height.get());
+        if (options.elevation.hasValue()) topBar.setElevation(options.elevation);
+
+        if (options.title.height.hasValue()) topBar.setTitleHeight(options.title.height.get());
         if (options.title.text.hasValue()) topBar.setTitle(options.title.text.get());
         if (options.title.component.hasValue()) topBar.setTitleComponent(options.title.component);
         if (options.title.color.hasValue()) topBar.setTitleTextColor(options.title.color.get());

lib/android/app/src/main/java/com/reactnativenavigation/views/topbar/TopBar.java

 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.graphics.Typeface;
+import android.os.Build;
 import android.support.annotation.ColorInt;
 import android.support.annotation.NonNull;
 import android.support.annotation.RestrictTo;
 import com.reactnativenavigation.parse.Component;
 import com.reactnativenavigation.parse.params.Button;
 import com.reactnativenavigation.parse.params.Color;
+import com.reactnativenavigation.parse.params.Fraction;
 import com.reactnativenavigation.parse.params.Number;
 import com.reactnativenavigation.utils.CompatUtils;
 import com.reactnativenavigation.utils.UiUtils;
     }
 
     public void setBackgroundColor(Color color) {
-        titleBar.setBackgroundColor(color);
+        if (!color.hasValue()) return;
+        setBackgroundColor(color.get());
+    }
+
+    public void setElevation(Fraction elevation) {
+        if (elevation.hasValue() &&
+            Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP &&
+            getElevation() != elevation.get().floatValue()) {
+            setElevation(UiUtils.dpToPx(getContext(), elevation.get().floatValue()));
+        }
     }
 
     public Toolbar getTitleBar() {

lib/android/app/src/test/java/com/reactnativenavigation/viewcontrollers/OptionsApplyingTest.java

 package com.reactnativenavigation.viewcontrollers;
 
 import android.app.Activity;
+import android.content.Context;
 import android.graphics.Color;
 import android.graphics.drawable.ColorDrawable;
 import android.view.View;
 import com.reactnativenavigation.parse.params.Fraction;
 import com.reactnativenavigation.parse.params.Text;
 import com.reactnativenavigation.utils.CommandListenerAdapter;
-import com.reactnativenavigation.utils.ViewUtils;
 import com.reactnativenavigation.viewcontrollers.topbar.TopBarBackgroundViewController;
 import com.reactnativenavigation.viewcontrollers.topbar.TopBarController;
-import com.reactnativenavigation.views.topbar.TopBarBackgroundView;
+import com.reactnativenavigation.views.StackLayout;
+import com.reactnativenavigation.views.titlebar.TitleBarReactViewCreator;
+import com.reactnativenavigation.views.topbar.TopBar;
 
 import org.json.JSONObject;
 import org.junit.Test;
 import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
 import static android.widget.RelativeLayout.BELOW;
 import static org.assertj.core.api.Java6Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 
 public class OptionsApplyingTest extends BaseTest {
     private Activity activity;
     private ComponentViewController uut;
     private IReactView view;
     private Options initialNavigationOptions;
+    private TopBarController topBarController;
+    private TopBar topBar;
 
     @Override
     public void beforeEach() {
                 (activity1, componentId, componentName) -> view,
                 initialNavigationOptions
         );
+        topBarController = new TopBarController() {
+            @Override
+            protected TopBar createTopBar(Context context, ReactViewCreator buttonCreator, TitleBarReactViewCreator titleBarReactViewCreator, TopBarBackgroundViewController topBarBackgroundViewController, TopBarButtonController.OnClickListener topBarButtonClickListener, StackLayout stackLayout) {
+                topBar = spy(super.createTopBar(context, buttonCreator, titleBarReactViewCreator, topBarBackgroundViewController, topBarButtonClickListener, stackLayout));
+                return topBar;
+            }
+        };
         stackController = new StackControllerBuilder(activity)
                 .setTopBarButtonCreator(new TopBarButtonCreatorMock())
                 .setTitleBarReactViewCreator(new TitleBarReactViewCreatorMock())
                 .setTopBarBackgroundViewController(new TopBarBackgroundViewController(activity, new TopBarBackgroundViewCreatorMock()))
-                .setTopBarController(new TopBarController())
+                .setTopBarController(topBarController)
                 .setId("stack")
                 .setInitialOptions(new Options())
                 .createStackController();
         opts.topBar.background.color = new com.reactnativenavigation.parse.params.Color(Color.RED);
         uut.mergeOptions(opts);
 
-        assertThat(((ColorDrawable) stackController.getTopBar().getTitleBar().getBackground()).getColor()).isEqualTo(Color.RED);
+        assertThat(((ColorDrawable) stackController.getTopBar().getBackground()).getColor()).isEqualTo(Color.RED);
     }
 
     @Test
 
     @Test
     public void appliesTopBarComponent() throws Exception {
+        disablePushAnimation(uut);
         JSONObject json = new JSONObject();
         json.put("component", new JSONObject().put("name","someComponent").put("componentId", "id"));
         uut.options.topBar.background = TopBarBackgroundOptions.parse(json);
         stackController.push(uut, new CommandListenerAdapter());
         uut.onViewAppeared();
 
-        assertThat(((ColorDrawable) stackController.getTopBar().getTitleBar().getBackground()).getColor()).isEqualTo(Color.TRANSPARENT);
-        assertThat(ViewUtils.findChildrenByClassRecursive(stackController.getTopBar(), TopBarBackgroundView.class)).isNotNull();
+        verify(topBar, times(1)).setBackgroundComponent(any());
     }
 
     @Test