Some app generate an error and phone shows transparent popup, which looks like system popup because it is persisted across all apps and even hide system buttons or keyboard.
Example of messages in the box:
Resource has been exhausted (e.g. check quota)
Is there a system setting to move notifications to notification area instead? Or complete hide it...
With the help of Andrew I launched the command:
adb shell "pm list packages -f"
to get the list of packages and then scanned for their properties (Bash script):
list='com.google.android.youtube com.viber.voip'
mkdir -p dump
for i in $list; do
adb.exe shell appops get $i |& tee -a dump/$i.txt
done
Then I searched for the keyword TOAST_WINDOW. for Youtube app it was:
Uid mode: COARSE_LOCATION: ignore
LEGACY_STORAGE: allow
VIBRATE: allow; time=+7h31m46s232ms ago; duration=+27ms
TAKE_AUDIO_FOCUS: allow; time=+28m45s847ms ago
WAKE_LOCK: allow; time=+1h13m24s504ms ago; duration=+9s138ms
TOAST_WINDOW: allow; time=+1h12m25s632ms ago; duration=-24855d3h14m7s312ms
START_FOREGROUND: allow; time=+82d1h9m54s814ms ago; duration=+2m34s513ms
USE_BIOMETRIC: allow; time=+40d0h55m4s406ms ago
The line:
WAKE_LOCK: allow; time=+1h13m24s504ms ago; duration=+9s138ms
probably tells that last toast was 1h ago with duration of 9s. It looks like what we experienced!
So I disabled the privilege:
# adb shell appops set com.google.android.youtube TOAST_WINDOW deny
# adb shell appops get com.google.android.youtube
...
TOAST_WINDOW: deny; time=+1h23m2s506ms ago; duration=-24855d3h14m7s312ms
I hope this solves the problem. IDK if an app upgrade resets user settings...
UPDATE this UI element is called Toast.
Seems the duration of a toast is hard-coded in Android sources: