Unfortunately, a targetNotFound event is not possible from an app-flow-perspective. We would constantly need to fire this event for each frame in which no target could be found, which would be of no use to you (It is actually the same behavior as checking if the onEnterFieldOfVision event on the target has not been fired).
The use case you are describing would require a server-based target recognition (commonly referred to as server-based visual search). A developer would send the current screen content to the server, and the server is then replying with a selection of targets that are most likely in the camera frame.
The feature is on our radar, but I cannot give you any more information on how and when you will be able to achieve this at this time unfortunately.
almost 10 years ago
Is there a way to trigger an objective-c/adnroid function if target image could not be found in a collection/assets bundle? Or may be you could advise me a better way to achive following:
Because there is a limit of 1000 target images in one collection I need my app to be able to switch between collections untill it finds the one that contains target image user is scanning. If target image is not found in default collection I want to swtich to another one and check there.