Misc ToolBar fixes

Minor refactor after merging #52.

android/app/src/main/java/com/reactnativenavigation/activities/BaseReactActivity.java

     @CallSuper
     public void push(Screen screen) {
         setNavigationStyle(screen);
-        if (mToolbar != null &&
-            getCurrentNavigatorId().equals(screen.navigatorId) &&
-            getScreenStackSize() >= 1) {
-            mToolbar.showBackButton(screen);
+        if (mToolbar != null) {
+            mToolbar.update(screen);
+
+            if (getCurrentNavigatorId().equals(screen.navigatorId) &&
+                getScreenStackSize() >= 1) {
+                mToolbar.showBackButton(screen);
+            }
         }
     }
 

android/app/src/main/java/com/reactnativenavigation/activities/BottomTabActivity.java

     }
 
     private void setupToolbar(ArrayList<Screen> screens) {
-        Screen initialScreen = screens.get(0);
         mToolbar.setScreens(screens);
-        mToolbar.updateToolbar(initialScreen);
+        Screen initialScreen = screens.get(0);
+        mToolbar.update(initialScreen);
         setNavigationStyle(initialScreen);
     }
 
-    @Override
-    public void setNavigationStyle(Screen screen) {
-        super.setNavigationStyle(screen);
-        mToolbar.setTitle(screen.title);
-    }
-
     private void setupTabs(Bundle style) {
 
         mBottomNavigation.setForceTitlesDisplay(style.getBoolean(TAB_STYLE_INACTIVE_TITLES, DEFAULT_TAB_INACTIVE_TITLES));
     @Override
     public void push(Screen screen) {
         super.push(screen);
-        setNavigationStyle(screen);
         mScreenStacks.get(mCurrentStackPosition).push(screen);
     }
 
     public Screen pop(String navigatorId) {
         super.pop(navigatorId);
         Screen screen = mScreenStacks.get(mCurrentStackPosition).pop();
-        setNavigationStyle(getCurrentScreen());
+        Screen currentScreen = getCurrentScreen();
+        setNavigationStyle(currentScreen);
+        mToolbar.update(currentScreen);
         return screen;
     }
 

android/app/src/main/java/com/reactnativenavigation/activities/SingleScreenActivity.java

     }
 
     protected void setupToolbar(Screen screen) {
-        mToolbar.updateToolbar(screen);
+        mToolbar.update(screen);
         setNavigationStyle(screen);
     }
     
     @Override
     public void push(Screen screen) {
         super.push(screen);
-        setNavigationStyle(screen);
         mScreenStack.push(screen);
     }
 
     public Screen pop(String navigatorId) {
         super.pop(navigatorId);
         Screen screen = mScreenStack.pop();
-        setNavigationStyle(getCurrentScreen());
+        Screen currentScreen = getCurrentScreen();
+        setNavigationStyle(currentScreen);
+        mToolbar.update(currentScreen);
         return screen;
     }
 

android/app/src/main/java/com/reactnativenavigation/activities/TabActivity.java

 import java.util.ArrayList;
 
 /**
+ * This class is currently not supported and will be removed in future release.
  * Created by guyc on 02/04/16.
  */
+@Deprecated
 public class TabActivity extends BaseReactActivity {
     public static final String EXTRA_SCREENS = "extraScreens";
 
     private void setupToolbar(ArrayList<Screen> screens) {
         Screen initialScreen = screens.get(0);
         mToolbar.setScreens(screens);
-        mToolbar.updateToolbar(initialScreen);
+        mToolbar.update(initialScreen);
         setNavigationStyle(initialScreen);
     }
 

android/app/src/main/java/com/reactnativenavigation/modal/RnnModal.java

 
     private ScreenStack mScreenStack;
     private View mContentView;
-    private Screen mScreen;
     private RnnToolBar mToolBar;
 
     public RnnModal(BaseReactActivity context, Screen screen) {
         super(context, R.style.Modal);
-        mScreen = screen;
         ModalController.getInstance().add(this);
-        init(context);
+        init(context, screen);
     }
 
     @SuppressLint("InflateParams")
-    private void init(final Context context) {
+    private void init(final Context context, Screen screen) {
         requestWindowFeature(Window.FEATURE_NO_TITLE);
         mContentView = LayoutInflater.from(context).inflate(R.layout.modal_layout, null, false);
         mToolBar = (RnnToolBar) mContentView.findViewById(R.id.toolbar);
         mScreenStack = (ScreenStack) mContentView.findViewById(R.id.screenStack);
         setContentView(mContentView);
-        mToolBar.updateToolbar(mScreen);
-        mScreenStack.push(mScreen, new RctView.OnDisplayedListener() {
+        mToolBar.update(screen);
+        mScreenStack.push(screen, new RctView.OnDisplayedListener() {
             @Override
             public void onDisplayed() {
                 Animation animation = AnimationUtils.loadAnimation(context, R.anim.slide_up);
         if (SdkSupports.lollipop()) {
             Window window = getWindow();
             window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
-            StyleHelper.setWindowStyle(window, context.getApplicationContext(), mScreen);
+            StyleHelper.setWindowStyle(window, context.getApplicationContext(), screen);
         }
     }
 
     public void push(Screen screen) {
         mScreenStack.push(screen);
-        mToolBar.updateToolbar(mScreen);
+        mToolBar.update(screen);
     }
 
     public Screen pop() {
-        if (mScreenStack.getStackSize() > 1) {
-            return mScreenStack.pop();
-        } else {
+        if (mScreenStack.isEmpty()) {
             ModalController.getInstance().remove();
             super.onBackPressed();
             return null;
+        } else {
+            return mScreenStack.pop();
         }
     }
 
     @Override
     public void onBackPressed() {
-        if (mScreenStack.getStackSize() > 1) {
-            mScreenStack.pop();
-        } else {
+        if (mScreenStack.isEmpty()) {
             ModalController.getInstance().remove();
             super.onBackPressed();
+        } else {
+            mScreenStack.pop();
         }
     }
 

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

 import com.reactnativenavigation.utils.ImageUtils;
 
 import java.lang.ref.WeakReference;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
         ContextProvider.getActivityContext().getSupportActionBar().setDisplayHomeAsUpEnabled(false);
     }
 
+    /**
+     * Update the ToolBar from screen. This function sets any properties that are defined
+     * in the screen.
+     * @param screen The currently displayed screen
+     */
     @UiThread
-    public void updateToolbar(Screen screen) {
-        setSupportActionBar();
+    public void update(Screen screen) {
+        ((AppCompatActivity) getContext()).setSupportActionBar(this);
         setTitle(screen.title);
         setStyle(screen);
         setupToolbarButtonsAsync(screen);
     }
 
-    private void setSupportActionBar() {
-        ((AppCompatActivity) getContext()).setSupportActionBar(this);
-    }
-
     private static class SetupToolbarButtonsTask extends AsyncTask<Void, Void, Map<String, Drawable>> {
         private final List<Button> mOldButtons;
         private final List<Button> mNewButtons;