How to observe specific folder for insertion or deletion in android?

Question

I am developing a whatsapp status saver app that let user download status from my app. I am able to fetch the files from my app but the problem is if user minimize my app and visit whatsapp to watch status then come back to my app they arent shown the new whatsapp status unless they close the app and open again. I am wishing for a way to keep on monitoring the status folder for any deletion or insertion irrespective of whether the app is in background or app is killed. Any guidance is highly appreciated.