Support adding react component to TopBar

Usage:
    navBarCustomView: 'example.CustomTopBar', // registered component name
    navBarComponentAlignment: 'center' // 'center'/'fill'

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

 import android.graphics.Typeface;
 import android.os.Bundle;
 import android.support.annotation.ColorInt;
+import android.text.TextUtils;
 
 import com.reactnativenavigation.utils.TypefaceLoader;
 
     public Color contextualMenuBackgroundColor;
 
     public Color topBarColor;
+    public String topBarReactView;
+    public String topBarReactViewAlignment;
     public CollapsingTopBarParams collapsingTopBarParams;
     public boolean topBarCollapseOnScroll;
     public boolean topBarElevationShadowEnabled;
     public Font bottomTabFontFamily;
 
     public Color navigationBarColor;
+
+    public boolean hasTopBarCustomComponent() {
+        return !TextUtils.isEmpty(topBarReactView);
+    }
 }

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

         result.contextualMenuBackgroundColor = getColor("contextualMenuBackgroundColor", getDefaultContextualMenuBackgroundColor());
 
         result.topBarColor = getColor("topBarColor", getDefaultTopBarColor());
+        result.topBarReactView = params.getString("topBarReactView");
+        result.topBarReactViewAlignment = params.getString("topBarReactViewAlignment");
         result.titleBarHideOnScroll = getBoolean("titleBarHideOnScroll", getDefaultTitleBarHideOnScroll());
         result.topBarTransparent = getBoolean("topBarTransparent", getDefaultTopBarHidden());
         result.topBarCollapseOnScroll = getBoolean("topBarCollapseOnScroll", false);

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

 
     private void createTitleBar() {
         addTitleBarButtons();
-        topBar.setTitle(screenParams.title);
-        topBar.setSubtitle(screenParams.subtitle);
+        if (screenParams.styleParams.hasTopBarCustomComponent()) {
+            topBar.setReactView(screenParams.styleParams.topBarReactView, screenParams.styleParams.topBarReactViewAlignment);
+        } else {
+            topBar.setTitle(screenParams.title);
+            topBar.setSubtitle(screenParams.subtitle);
+        }
     }
 
     private void addTitleBarButtons() {

android/app/src/main/java/com/reactnativenavigation/utils/ViewUtils.java

 public class ViewUtils {
     private static final AtomicInteger viewId = new AtomicInteger(1);
     private static int statusBarHeight = -1;
+    private static int toolBarHeight = -1;
 
     public static void runOnPreDraw(final View view, final Runnable task) {
         view.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
     public static float getWindowHeight(Activity activity) {
         DisplayMetrics metrics = new DisplayMetrics();
         activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);
-        return metrics.widthPixels;
+        return metrics.heightPixels;
     }
 
     private static int compatGenerateViewId() {
         return statusBarHeight;
     }
 
+    public static int getToolBarHeight() {
+        if (toolBarHeight > 0) {
+            return toolBarHeight;
+        }
+        final Resources resources = NavigationApplication.instance.getResources();
+        final int resourceId = resources.getIdentifier("action_bar_size", "dimen", "android");
+        toolBarHeight = resourceId > 0 ?
+                resources.getDimensionPixelSize(resourceId) :
+                (int) convertDpToPixel(56);
+        return toolBarHeight;
+    }
+
+
     public static ForegroundColorSpan[] getForegroundColorSpans(TextView view) {
         SpannedString text = new SpannedString(view.getText());
         return text.getSpans(0, text.length(), ForegroundColorSpan.class);

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

     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
         int measuredHeight = viewMeasurer.getMeasuredHeight(heightMeasureSpec);
-        setMeasuredDimension(viewMeasurer.getMeasuredWidth(widthMeasureSpec),
-                measuredHeight);
+        setMeasuredDimension(viewMeasurer.getMeasuredWidth(widthMeasureSpec), measuredHeight);
     }
 
     @Override

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

         addButtonsToTitleBar(navigatorEventId, menu);
     }
 
+    public int getRightButtonsWidth() {
+        return actionMenuView.getWidth();
+    }
+
     public void setLeftButton(TitleBarLeftButtonParams leftButtonParams,
                               LeftButtonOnClickListener leftButtonOnClickListener,
                               String navigatorEventId,

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

 import android.content.Context;
 import android.graphics.Color;
 import android.os.Build;
+import android.os.Bundle;
 import android.support.design.widget.AppBarLayout;
+import android.support.v7.app.ActionBar;
+import android.text.TextUtils;
+import android.view.Gravity;
 import android.view.ViewGroup;
 import android.widget.FrameLayout;
 
 import com.reactnativenavigation.animation.VisibilityAnimator;
 import com.reactnativenavigation.params.BaseScreenParams;
 import com.reactnativenavigation.params.ContextualMenuParams;
+import com.reactnativenavigation.params.NavigationParams;
 import com.reactnativenavigation.params.StyleParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
 import com.reactnativenavigation.params.TitleBarLeftButtonParams;
+import com.reactnativenavigation.screens.Screen;
 import com.reactnativenavigation.utils.ViewUtils;
 
 import java.util.List;
         titleBar.setSubtitle(subtitle);
     }
 
+    public void setReactView(String topBarReactView, String alignment) {
+        if (!TextUtils.isEmpty(topBarReactView)) {
+            final ContentView view = new ContentView(getContext(), topBarReactView, new NavigationParams(Bundle.EMPTY));
+            if ("fill".equals(alignment)) {
+                addReactViewFill(view);
+            } else {
+                addCenteredReactView(view);
+            }
+        }
+    }
+
+    private void addReactViewFill(ContentView view) {
+        view.setLayoutParams(new LayoutParams(MATCH_PARENT, ViewUtils.getToolBarHeight()));
+        titleBar.addView(view);
+    }
+
+    private void addCenteredReactView(final ContentView view) {
+        titleBar.addView(view, new LayoutParams(WRAP_CONTENT, ViewUtils.getToolBarHeight()));
+        view.setOnDisplayListener(new Screen.OnDisplayListener() {
+            @Override
+            public void onDisplay() {
+                view.getLayoutParams().width = (int) (float) view.getChildAt(0).getMeasuredWidth();
+                ((ActionBar.LayoutParams) view.getLayoutParams()).gravity = Gravity.CENTER;
+                view.requestLayout();
+            }
+        });
+    }
+
     public void setButtonColor(StyleParams styleParams) {
         titleBar.setButtonColor(styleParams.titleBarButtonColor);
     }

src/deprecated/platformSpecificDeprecated.android.js

   let ret = {
     orientation: originalStyleObject.orientation,
     statusBarColor: processColor(originalStyleObject.statusBarColor),
+    topBarReactView: originalStyleObject.navBarCustomView,
+    topBarReactViewAlignment: originalStyleObject.navBarComponentAlignment,
     topBarColor: processColor(originalStyleObject.navBarBackgroundColor),
     topBarTransparent: originalStyleObject.navBarTransparent,
     topBarTranslucent: originalStyleObject.navBarTranslucent,