Hi @ratanapouy,
Could you please share a bit more about the first screen (Detail Screen) that you mentioned within your app?
Further, could you please show a bit more about the formula within Items property of the Display form of your Detail screen?
I have made a test on my side, please take a try with the following workaround:
Within Gallery screen (Screen1):
set Items property of the Gallery control (Gallery1) to my SP list data source. Set OnSelect property of Navigate button to following formula:
Navigate(Screen2,ScreenTransition.Fade)
Within Detail Screen (Screen2):
Set Item property of the Display form control to following formula:
Gallery1.Selected
Set OnSelect property of the "Has Attachments" Label control (On your side, it is "Attachment") to following formula:
If(Gallery1.Selected.'{HasAttachments}'=true,Navigate(Screen3,ScreenTransition.Fade))
Within Attachments Preview screen (Screen3):
Set Items property of the Gallery control (Gallery2) to following formula:
Gallery1.Selected.'{Attachments}'
Set the Image property of the Image control within the Gallery control (Gallery2) to following formula:
ThisItem.AbsoluteUri
If you could provide more details about your scenario, we would provided a proper workaround for you.
Best regards,
Kris
