[AC Question]

So I use DU Speed Booster to improve my memory usage and I think It deleted something to do with the cache or media database because my music library and gallery are empty yet all the files are still there. I have a Sony Xperia Z.

[B. Diddy]

Welcome to Android Central! First, I would strongly suggest getting rid of any "booster" apps. These apps claim to improve memory usage and performance, but they typically just close apps out of RAM on an automatic basis, ignoring the fact that Android is designed to keep RAM relatively full of open apps. So if the booster app closes apps from RAM, the system will just open them again. This sets up a cycle of close-open-close-open that ultimately drains battery.

Second, go to Settings>Apps>All​, select the Music and Gallery apps, and Clear Cache/Clear Data from both of them, then Force Stop. Now open them again and wait a few seconds for the databases to repopulate. Do they display properly now?