fixed push pop mechanism

android/app/src/main/java/com/reactnativenavigation/controllers/NavigationCommandsHandler.java

 
     private static final String ACTIVITY_PARAMS_BUNDLE = "ACTIVITY_PARAMS_BUNDLE";
 
+    static ActivityParams getActivityParams(Intent intent) {
+        return ActivityParamsParser.parse(intent.getBundleExtra(NavigationCommandsHandler.ACTIVITY_PARAMS_BUNDLE));
+    }
+
     /**
      * start a new activity with CLEAR_TASK | NEW_TASK
      *
         });
     }
 
-    static ActivityParams getActivityParams(Intent intent) {
-        return ActivityParamsParser.parse(intent.getBundleExtra(NavigationCommandsHandler.ACTIVITY_PARAMS_BUNDLE));
-    }
 
     public static void pop(Bundle screenParams) {
         final NavigationActivity currentActivity = NavigationActivity.currentActivity;

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

 public interface Screen {
     View asView();
 
+    void preventUnmountOnDetachedFromWindow();
+
     void ensureUnmountOnDetachedFromWindow();
 }

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

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

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

     }
 
     public void push(ScreenParams screenParams) {
+        Screen previous = stack.peek();
+        addScreen(screenParams);
+        removePreviousWithoutUnmount(previous);
+    }
+
+    private void addScreen(ScreenParams screenParams) {
         Screen screen = new ScreenImpl(getContext(), screenParams);
         addView(screen.asView(), new FrameLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT));
         stack.push(screen);
     }
 
-    public Screen pop() {
-        Screen popped = stack.pop();
-        popped.ensureUnmountOnDetachedFromWindow();
-        removeView(popped.asView());
-        return popped;
+    private void removePreviousWithoutUnmount(Screen previous) {
+        previous.preventUnmountOnDetachedFromWindow();
+        removeView(previous.asView());
+    }
+
+    public void pop() {
+        if (!canPop()) {
+            throw new RuntimeException("Can't pop ScreenStack of size " + getStackSize());
+        }
+
+        Screen toRemove = stack.pop();
+        Screen previous = stack.peek();
+
+        readdPrevious(previous);
+
+        toRemove.ensureUnmountOnDetachedFromWindow();
+        removeView(toRemove.asView());
+    }
+
+    private void readdPrevious(Screen previous) {
+        addView(previous.asView(), new LayoutParams(MATCH_PARENT, MATCH_PARENT));
     }
 
     public void popToRoot() {
     }
 
     public void destroy() {
-        while (!isEmpty()) {
-            pop();
+        for (Screen screen : stack) {
+            screen.ensureUnmountOnDetachedFromWindow();
+            removeView(screen.asView());
         }
+        stack.clear();
     }
 
     public boolean isEmpty() {
         return stack.size();
     }
 
-    public Screen peek() {
-        return stack.peek();
-    }
-
     public boolean canPop() {
         return getStackSize() > 1;
     }