protected override void OnElementChanged(ElementChangedEventArgs <TabbedPage> e) { base.OnElementChanged(e); var activity = Context.GetActivity(); var isDesigner = Context.IsDesignerContext(); var themeContext = isDesigner ? Context : activity; if (e.OldElement != null) { ((IPageController)e.OldElement).InternalChildren.CollectionChanged -= OnChildrenCollectionChanged; } if (e.NewElement != null) { if (IsBottomTabPlacement) { if (_relativeLayout == null) { _relativeLayout = new AWidget.RelativeLayout(Context) { LayoutParameters = new LayoutParams(LayoutParams.MatchParent, LayoutParams.MatchParent), }; if (_bottomNavigationView != null) { _relativeLayout.RemoveView(_bottomNavigationView); _bottomNavigationView.SetOnNavigationItemSelectedListener(null); } var bottomNavigationViewLayoutParams = new AWidget.RelativeLayout.LayoutParams( LayoutParams.MatchParent, LayoutParams.WrapContent); bottomNavigationViewLayoutParams.AddRule(AWidget.LayoutRules.AlignParentBottom); _bottomNavigationView = new BottomNavigationView(Context) { LayoutParameters = bottomNavigationViewLayoutParams, Id = Platform.GenerateViewId() }; var viewPagerParams = new AWidget.RelativeLayout.LayoutParams(LayoutParams.MatchParent, LayoutParams.MatchParent); viewPagerParams.AddRule(AWidget.LayoutRules.Above, _bottomNavigationView.Id); FormsViewPager pager = _viewPager = CreateFormsViewPager(themeContext, e.NewElement); pager.Id = Platform.GenerateViewId(); pager.AddOnPageChangeListener(this); _relativeLayout.AddView(pager, viewPagerParams); _relativeLayout.AddView(_bottomNavigationView, bottomNavigationViewLayoutParams); AddView(_relativeLayout); } } else { if (_tabLayout == null) { TabLayout tabs; if (FormsAppCompatActivity.TabLayoutResource > 0 && !isDesigner) { tabs = _tabLayout = activity.LayoutInflater.Inflate(FormsAppCompatActivity.TabLayoutResource, null).JavaCast <TabLayout>(); } else { tabs = _tabLayout = new TabLayout(themeContext) { TabMode = TabLayout.ModeFixed, TabGravity = TabLayout.GravityFill } }; FormsViewPager pager = _viewPager = CreateFormsViewPager(themeContext, e.NewElement); pager.Id = Platform.GenerateViewId(); pager.AddOnPageChangeListener(this); AddView(pager); AddView(tabs); } } OnChildrenCollectionChanged(null, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)); TabbedPage tabbedPage = e.NewElement; if (tabbedPage.CurrentPage != null) { ScrollToCurrentPage(); } _previousPage = tabbedPage.CurrentPage; ((IPageController)tabbedPage).InternalChildren.CollectionChanged += OnChildrenCollectionChanged; UpdateBarBackgroundColor(); UpdateBarBackground(); UpdateBarTextColor(); UpdateItemIconColor(); if (!isDesigner) { UpdateSwipePaging(); UpdateOffscreenPageLimit(); } } }