How to check which item in Gridview is in view

Question

Hello,

I am building a calendar and put the months into a GridView. How to get the current month Item in view from code behind? Kind of like the opposite of ScrollIntoView?

Thanks.

Answer 1

Hi Helen.W ,

According to your description, i guess you wonder such a function that while users scroll your gridview, you want to get the current month item in view from code behind without users select a item.

If so, would you mind to share the display style of your gridview? Does your gridview display an item once? 

If your gridview display the item regularly, I advise you to use ScrollViewer as a container and place your GridView in it. Then you could use ScrollViewer.ViewerChanged event to monitor if the GridView item in view is changed.

XAML of Sample :

 <ScrollViewer x:Name="scroll" Width="100" Height="100" Grid.Row="1" VerticalAlignment="Center" HorizontalAlignment="Center" ViewChanged="scroll_ViewChanged">
             <GridView x:Name="grid" ScrollViewer.HorizontalScrollMode="Auto" Grid.Row="1" VerticalAlignment="Center" HorizontalAlignment="Center" ItemClick="grid_ItemClick" IsItemClickEnabled="True" />
        </ScrollViewer>

Code behind of Sample:

 private void scroll_ViewChanged(object sender, ScrollViewerViewChangedEventArgs e)
        {
            ScrollViewer scr = (ScrollViewer)sender;
            double horoffset = scr.HorizontalOffset;//if your scrollviewer is display horizontally
            double veroffset = scr.VerticalOffset; //if your scrollviewer is display vertically
            //please calculate the relative displacement and calculate the index of items by (relative displacement/item's height or with)
        }

If you are afraid only part of item is in the view, please use ScrollIntoView for help.

If you need more help, please let me know!

Best Regards!

Answer 2

Thanks Xiaoliang.

But the statement you commented is really what I don't know. ScrollViewer has its own rules to displace certain number of rows per page. For example, it may show all months in one row, or show them in 2 rows. And I didn't see GridViewItem has a property HorizontalOffset/VerticalOffset showing how far it's from the edge of the parent ScrollViewer.

Thanks for further explanation in advance.

Answer 3

Hi Helen.W ,

HorizontalOffset/VerticalOffset is the property of ScrollViewer. And HorizontalOffset/VerticalOffset is Relative displacement of the rolling on ScrollViewer. When you view a item per in ScrollViewer, you could get the index of items. Please set the item fill ScrollViewer. Then you could get the exact relative displacement.

Please just have a try!

Best Regards!