Lost images after synchronizing

I accidentally delete Ankidroid folder on my tablet including AnkiDroid/collection.media and was forced to resynchronize the empty app to bring back my cards but after it finished all cards are back except for pics in the cards. How is that synchronizing can bring back cards but not media? What should I do?

Your AnkiWeb account is not showing any deletions, so I presume you resolved your issue. If not, what does the check media tool say?

Two of my decks were shared decks so I delete and download them again to restart. but one of my decks is created by myself so actually the problem still exist for that deck. All media are gone in it.

Since they’re not showing as deletions, that implies they were never uploaded to AnkiWeb, and I’m afraid there is nothing that can be done on this end.

Why they did not upload to Ankiweb? How can I be sure that this will not happen again? I just check and did not find anything wrong with synchronising setting.

One possibility is you had media syncing turned off in the preferences. You can check things have synced correctly in the future by confirming media appears when reviewing on AnkiWeb.