I had app where you can read books from pdf url, fnd it worked well but book loads everytime i open book read page, then i wanted to save pdf first time i open page, and i was watching some tutorial for it, and first thing i did was that i declared this line in Manifest "
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
"
Then without writing any code i launched app but the books did not load as if there was no internet connection, but there was! So then i deleted that Write External Storage stroke and issue did not gone, from there i can't load books as i did usual.
SOLUTION: The solution was simple, and it's here: https://stackoverflow.com/a/49953004/19915097
Also good explanation of how loading data from firebase database works: https://stackoverflow.com/a/47853774/19915097
