protected virtual void OnPopViewModel(IPageViewModel viewModel, bool animated)
{
if (PageReferences.LastOrDefault()?.Model != viewModel)
{
throw new Exception(String.Format("The viewModel is not the last in the stack: {0}", viewModel));
}
var pageReference = PageReferences.LastOrDefault();
PageReferences.RemoveAt(PageReferences.Count - 1);
if (this.Navigation.NavigationStack.LastOrDefault() == pageReference.View)
{
PopAsync();
}
}
void _pages_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
bool wasResetting = resetting;
resetting = false;
if (e.Action == NotifyCollectionChangedAction.Add)
{
if (wasResetting && e.NewItems.OfType <IPageViewModel> ().FirstOrDefault() == PageReferences.FirstOrDefault()?.Model)
{
OnPopToRoot(Pages.LastOrDefault(), TransitionAnimationEnabled);
}
else if (wasResetting)
{
OnPopToNewRoot(e.NewItems.OfType <IPageViewModel> ().LastOrDefault(), TransitionAnimationEnabled);
}
else
{
OnPushViewModel(e.NewItems.OfType <IPageViewModel> ().LastOrDefault(), TransitionAnimationEnabled);
}
}
else if (e.Action == NotifyCollectionChangedAction.Remove)
{
if (PageReferences.LastOrDefault()?.Model == e.OldItems.OfType <IPageViewModel> ().LastOrDefault() && e.OldItems.Count == 1)
{
OnPopViewModel(e.OldItems.OfType <IPageViewModel> ().LastOrDefault(), TransitionAnimationEnabled);
}
else
{
PageReferences.RemoveAll(r => e.OldItems.Contains(r.Model));
}
}
else if (e.Action == NotifyCollectionChangedAction.Reset)
{
resetting = true;
}
}
async void updatePages()
{
if (_pages != null && _pages.Count > 0)
{
foreach (var pref in PageReferences.Where(p => !_pages.Contains(p.Model)).ToList())
{
PageReferences.Remove(pref);
}
if (new[] { this.Navigation.NavigationStack.FirstOrDefault(), this.Navigation.NavigationStack.LastOrDefault(), PageReferences.LastOrDefault()?.View }
.All(v => v == PageReferences.FirstOrDefault()?.View))
{
OnPopToRoot(Pages.LastOrDefault(), TransitionAnimationEnabled);
}
else
{
if (Navigation.NavigationStack.Count > 0)
{
var pref = createPageFor(Pages.LastOrDefault());
PageReferences.Clear();
PageReferences.Add(pref);
await popToNewRootAsync(pref.View, TransitionAnimationEnabled);
}
else
{
OnPushViewModel(Pages.LastOrDefault(), TransitionAnimationEnabled);
}
}
}
else
{
//At least on page should be displayed
PageReferences.Clear();
var blankPage = new ContentPage {
BackgroundColor = Color.Transparent
};
if (Navigation.NavigationStack.Count > 0)
{
await popToNewRootAsync(blankPage, TransitionAnimationEnabled);
}
else
{
await PushAsync(blankPage, TransitionAnimationEnabled);
}
}
}
