Additional work on BottomTabs

android/app/src/main/java/com/reactnativenavigation/layouts/BottomTabsLayout.java

 import android.widget.RelativeLayout;
 
 import com.aurelhubert.ahbottomnavigation.AHBottomNavigation;
-import com.aurelhubert.ahbottomnavigation.AHBottomNavigationItem;
 import com.reactnativenavigation.params.ActivityParams;
 import com.reactnativenavigation.params.ScreenParams;
 import com.reactnativenavigation.params.TitleBarButtonParams;
     private final AppCompatActivity activity;
     private ActivityParams params;
     private BottomTabs bottomTabs;
-    private ArrayList<ScreenStack> screenStacks;
+    private ScreenStack[] screenStacks;
     private int currentStackIndex = 0;
 
     public BottomTabsLayout(AppCompatActivity activity, ActivityParams params) {
         super(activity);
         this.activity = activity;
         this.params = params;
-        screenStacks = new ArrayList<>();
+        screenStacks = new ScreenStack[(params.tabParams.size())];
         createLayout();
     }
 
     private void createBottomTabs() {
         bottomTabs = new BottomTabs(getContext());
         setBottomTabsStyle();
-        addTabs();
+        bottomTabs.addTabs(params.tabParams, this);
     }
 
     private void addBottomTabsToScreen() {
     }
 
     private void addInitialScreen() {
-        addView(getFirstScreenStack());
+        createAndAddScreenStack(0);
     }
 
     private void setBottomTabsStyle() {
 //        bottomTabs.setAccentColor(getColor(style, TAB_STYLE_SELECTED_COLOR, DEFAULT_TAB_SELECTED_COLOR));
     }
 
-    private void addTabs() {
-        for (ScreenParams screenParams : params.tabParams) {
-            ScreenStack stack = new ScreenStack(activity, screenParams);
-            screenStacks.add(stack);
-
-            AHBottomNavigationItem item = new AHBottomNavigationItem(screenParams.title, screenParams.tabIcon,
-                    Color.GRAY);
-            bottomTabs.addItem(item);
-            bottomTabs.setOnTabSelectedListener(this);
-        }
-    }
-
     @Override
     public View asView() {
         return this;
 
     @Override
     public boolean onBackPressed() {
-        return false;
+        if (getCurrentScreenStack().canPop()) {
+            getCurrentScreenStack().pop();
+            return true;
+        } else {
+            return false;
+        }
     }
 
     @Override
     public void setTopBarVisible(String screenInstanceId, boolean hidden, boolean animated) {
         for (int i = 0; i < bottomTabs.getItemsCount(); i++) {
-            screenStacks.get(i).setTopBarVisible(screenInstanceId, hidden, animated);
+            screenStacks[i].setTopBarVisible(screenInstanceId, hidden, animated);
         }
     }
 
     @Override
     public void setTitleBarTitle(String screenInstanceId, String title) {
         for (int i = 0; i < bottomTabs.getItemsCount(); i++) {
-            screenStacks.get(i).setTitleBarTitle(screenInstanceId, title);
+            screenStacks[i].setTitleBarTitle(screenInstanceId, title);
         }
     }
 
     @Override
     public void setTitleBarRightButtons(String screenInstanceId, String navigatorEventId, List<TitleBarButtonParams> titleBarButtons) {
         for (int i = 0; i < bottomTabs.getItemsCount(); i++) {
-            screenStacks.get(i).setTitleBarRightButtons(screenInstanceId, navigatorEventId, titleBarButtons);
+            screenStacks[i].setTitleBarRightButtons(screenInstanceId, navigatorEventId, titleBarButtons);
         }
     }
 
     @Override
     public void setTitleBarLeftButton(String screenInstanceId, String navigatorEventId, TitleBarLeftButtonParams titleBarLeftButtonParams) {
         for (int i = 0; i < bottomTabs.getItemsCount(); i++) {
-            screenStacks.get(i).setTitleBarLeftButton(screenInstanceId, navigatorEventId, titleBarLeftButtonParams);
+            screenStacks[i].setTitleBarLeftButton(screenInstanceId, navigatorEventId, titleBarLeftButtonParams);
         }
     }
 
         currentScreenStack.destroy();
         removeView(currentScreenStack);
 
-        ScreenStack newStack = new ScreenStack(activity, params);
-        screenStacks.set(currentStackIndex, newStack);
+        ScreenStack newStack = new ScreenStack(getContext(), params);
+        screenStacks[currentStackIndex] = newStack;
         addView(newStack, 0, new RelativeLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT));
     }
 
     @Override
     public void destroy() {
-
+        for (ScreenStack screenStack : screenStacks) {
+            screenStack.destroy();
+            removeView(screenStack);
+        }
+        screenStacks = null;
     }
 
     @Override
     public void onTabSelected(int position, boolean wasSelected) {
-        removeView(getCurrentScreenStack());
-        addView(screenStacks.get(position), 0, new LayoutParams(MATCH_PARENT, MATCH_PARENT));
+        removeCurrentStack();
+
+        ScreenStack newStack = screenStacks[position];
+        if (newStack == null) {
+            createAndAddScreenStack(position);
+        } else {
+            addView(newStack, 0, new LayoutParams(MATCH_PARENT, MATCH_PARENT));
+            newStack.preventMountAfterReatachedToWindow();
+        }
         currentStackIndex = position;
     }
 
-    private ScreenStack getCurrentScreenStack() {
-        return screenStacks.get(currentStackIndex);
+    private void createAndAddScreenStack(int position) {
+        ScreenStack newStack = new ScreenStack(getContext(), params.tabParams.get(position));
+        screenStacks[position] = newStack;
+        addView(newStack, 0, new LayoutParams(MATCH_PARENT, MATCH_PARENT));
     }
 
-    private ScreenStack getFirstScreenStack() {
-        return screenStacks.get(0);
+    private void removeCurrentStack() {
+        ScreenStack currentScreenStack = getCurrentScreenStack();
+        currentScreenStack.preventUnmountOnDetachedFromWindow();
+        removeView(currentScreenStack);
+    }
+
+    private ScreenStack getCurrentScreenStack() {
+        return screenStacks[currentStackIndex];
     }
 }

android/app/src/main/java/com/reactnativenavigation/react/ReactViewHacks.java

     }
 
     /**
-     * Must be called before view is removed from screen inorder to ensure onDetachedFromScreen is properly
-     * executed and componentWillUnmount is called
+     * Side effect: prevents JS components constructor from being called
      */
     public static void ensureUnmountOnDetachedFromWindow(ReactRootView view) {
         ReflectionUtils.setField(view, "mAttachScheduled", false);
     }
 
+    /**
+     * Side effect: ensures unmount will be called
+     */
+    public static void preventMountAfterReattachedToWindow(ReactRootView view) {
+        ReflectionUtils.setField(view, "mAttachScheduled", false);
+    }
+
 }

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

 
     public abstract void preventUnmountOnDetachedFromWindow();
 
+    public abstract void preventMountAfterReattachedToWindow();
+
     public String getScreenInstanceId() {
         return screenParams.screenInstanceId;
     }

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

             pop();
         }
     }
+
+    public void preventUnmountOnDetachedFromWindow() {
+        for (Screen screen : stack) {
+            screen.preventUnmountOnDetachedFromWindow();
+        }
+    }
+
+    public void ensureUnmountOnDetachedFromWindow() {
+        for (Screen screen : stack) {
+            screen.ensureUnmountOnDetachedFromWindow();
+        }
+    }
+
+    public void preventMountAfterReatachedToWindow() {
+        for (Screen screen : stack) {
+            screen.preventMountAfterReattachedToWindow();
+        }
+    }
 }

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

     public void preventUnmountOnDetachedFromWindow() {
         contentView.preventUnmountOnDetachedFromWindow();
     }
+
+    @Override
+    public void preventMountAfterReattachedToWindow() {
+        contentView.preventMountAfterReattachedToWindow();
+    }
 }

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

         }
     }
 
+    @Override
+    public void preventMountAfterReattachedToWindow() {
+        for (ContentView contentView : contentViews) {
+            contentView.preventMountAfterReattachedToWindow();
+        }
+    }
 
     public class ContentViewPagerAdapter extends PagerAdapter implements TabLayout.OnTabSelectedListener, ViewPager.OnPageChangeListener {
 

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

 package com.reactnativenavigation.views;
 
 import android.content.Context;
+import android.graphics.Color;
 
 import com.aurelhubert.ahbottomnavigation.AHBottomNavigation;
+import com.aurelhubert.ahbottomnavigation.AHBottomNavigationItem;
+import com.reactnativenavigation.params.ScreenParams;
+
+import java.util.List;
 
 public class BottomTabs extends AHBottomNavigation {
     public BottomTabs(Context context) {
         super(context);
     }
+
+    public void addTabs(List<ScreenParams> params, OnTabSelectedListener onTabSelectedListener) {
+        for (ScreenParams screenParams : params) {
+            AHBottomNavigationItem item = new AHBottomNavigationItem(screenParams.title, screenParams.tabIcon,
+                    Color.GRAY);
+            addItem(item);
+            setOnTabSelectedListener(onTabSelectedListener);
+        }
+    }
 }

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

     public void ensureUnmountOnDetachedFromWindow() {
         ReactViewHacks.ensureUnmountOnDetachedFromWindow(this);
     }
+
+    public void preventMountAfterReattachedToWindow() {
+        ReactViewHacks.preventMountAfterReattachedToWindow(this);
+    }
 }