QLPreviewController loses touch after presenting a modal view controller over it

Question

In an iPad master-detail application (the master is an UITableViewController and the detail a QLPreviewController) whenever I present a view controller modally and then dismiss it, the QLPreviewController stops receiving touch events or at least reacting to them. So, it's no longer possible to zoom in or out, or "bouncing" an image/document currently being shown, even after another image/document is selected and shown.

Keep in mind that before presenting the view controller modally everything works as expected and it's possible to zoom in/out.

Anyone knows a possible solution for this weird problem?

EDIT: added that this happens after dismissing the view controller presented modally.

EDIT 2: if the presentation style is UIModalPresentationFormSheet, the problem does not occur. It seems to only occur with UIModalPresentationFullScreen.

Answer 1

Although not a solution for this problem, a workaround is to present the view controller as UIModalPresentationFormSheet instead of fullscreen.

Answer 2

Yes that is expected behaviour.

When a ViewController is presented modally (I assume you are presenting something in a form sheet?), it prevents other view controllers receiving touch events.

The other alternative is to have a look at child view controllers as an alternative; but again, their touch events will take precedence over anything underneath.