Restore state of listview connected with CollectionViewSource

Question

Hi it's 10 days that I'm stuck on saving and restoring state of ListView connected to collection ViewSource
there's nothing special... the problem is that when I try to restore state save scrollview(extracting from ListView) position (VerticalOffset), then restoring, the position of scroll is wrong, so for eg. items in the middle of the listview are wrong.
In few words all seem works, I mean saving and restoring,  but actually the scroll position is completely wrong, when I try to restore scrollposition near middle of the list, if the position to restore is near bottom or top it works fine.
So, I mean, if I scrolled near item in the middle, then suspending and resuming the position is not right but is some items down...
the listview is groupped with albums (group ) and songs (item), nothing special, here's a piece of code
restore
/// <summary>
       /// Invoked when this page is about to be displayed in a Frame.
       /// </summary>
       /// <param name="e">Event data that describes how this page was reached.
       /// This parameter is typically used to configure the page.</param>
       protected override void OnNavigatedTo(NavigationEventArgs e)
           //RESTORE
           if (!string.IsNullOrWhiteSpace(_pageKey)) return;   //vuol dire che lo stato è caricato e non necessita altro
           this._pageKey = "PageSongView";
           var frameState = SuspensionManager.SessionStateForFrame(this.Frame);
           if (frameState.ContainsKey(_pageKey))
               var pageState = frameState[_pageKey] as Dictionary<String, Object>;
               if (pageState.ContainsKey("AlbumListIn.VerticalOffset"))
                   var v_offset = (double?)pageState["AlbumListIn.VerticalOffset"];
                   AlbumListIn.Loaded += (snd, arg) =>
                       var scroll_viewer = VisualTreeHelperEx.ScanVisualTree<ScrollViewer>(AlbumListIn).First();
                       scroll_viewer.Loaded += (snd2, arg2) =>
                          scroll_viewer.ChangeView(null, v_offset, null, false);
save
protected override void OnNavigatedFrom(NavigationEventArgs e)
//SAVE
var frameState = SuspensionManager.SessionStateForFrame(this.Frame);
var pageState = new Dictionary<String, Object>();
_saveState(pageState);
frameState[_pageKey] = pageState;
private void _saveState(Dictionary<string, object> pageState)
var scroll_viewer = VisualTreeHelperEx.ScanVisualTree<ScrollViewer>(AlbumListIn).First();
pageState["AlbumListIn.VerticalOffset"] = (double?)scroll_viewer.VerticalOffset;
var k = 0;
in the xaml
<ListView x:Name="AlbumListIn"
ItemsSource="{Binding Source={StaticResource AlbumCollection}}"
XamlHlp:XamlHelper.SetItemsCommand="{Binding Path=VM.SongItemControl.SelectedSongItemsCommand, Source={StaticResource SongService}}"
SelectionMode="{Binding Path=VM.SongItemControl.IsMultipleSelection, Source={StaticResource SongService},Converter={StaticResource BoolSelMode}}"
Style="{StaticResource AlbumSongZoomInStyle}"
>
<ListView.GroupStyle>
<GroupStyle HeaderTemplate="{StaticResource AlbumListGroupHeaderDT }">
</GroupStyle>
</ListView.GroupStyle>
</ListView>
please help me I'm really stuck and I don't find any solution...

Answer 1

>In few words all seem works, I mean saving and restoring,  but actually the scroll position is completely wrong, when I try to restore scrollposition near middle of the list, if the position to restore is near bottom or top it works fine.
I think this may be due to cached UI layout, this need to measure again manually: 
https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.uielement.measure.aspx?f=255&MSPPError=-2147217396
https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.uielement.arrange.aspx
If the above methods are not working, share a demo.
Best Regards,
Please remember to mark the replies as answers if they help