GridView.ScrollIntoView() doesn't work

I am writing an application which contains two pages, GroupedItemsPage and ItemDetailPage. I let lots of pictures present in the GroupItemsPage, then after select a specified picture in this page, it will nevigate the the second page withe the details showing for the selected picture. Since I put too much pictures in the first page, therefore the gridview always put the top picutres into view each time I goback to the first page. even the picture I selected previously are the last picture which need a scroll to the end.

I tried to use GridView.ScrollIntoView() in the LoadState method, my codes like below.

protected override void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)
        {
            // TODO: Create an appropriate data model for your problem domain to replace the sample data
            var sampleDataGroups = SampleDataSource.GetGroups((String)navigationParameter);
            this.DefaultViewModel["Groups"] = sampleDataGroups;

            if (pageState!=null&&pageState.ContainsKey("SelectedItem"))
            {
                SelectedItemId = pageState["SelectedItem"].ToString ();                var sampleDataItem = SampleDataSource.GetItem(SelectedItemId);
                //SampleDataGroup group = ((SampleDataItem)sampleDataItem).Group;
                //groupedItemsViewSource.View.MoveCurrentTo(group);

                itemGridView.ScrollIntoView(sampleDataItem);   
            }
        }

however, nomatter what I do, it just doesn't work.

then I moved the method call to Loaded event like below. It works:

  public GroupedItemsPage()
        {
            this.InitializeComponent();
            Loaded += GroupedItemsPage_Loaded;
        }

        void GroupedItemsPage_Loaded(object sender, RoutedEventArgs e)
        {
            if (SelectedItemId!=null&&SelectedItemId != string.Empty)
            {
                var sampleDataItem = SampleDataSource.GetItem(SelectedItemId);
                //SampleDataGroup group = ((SampleDataItem)sampleDataItem).Group;
                //groupedItemsViewSource.View.MoveCurrentTo(group);

                itemGridView.ScrollIntoView(sampleDataItem);    
            }
        }