Volume Button Issue

[tube]

I noticed that the volume button of the Xperia X compact (model F5321, Build number 34.3.A.0.252, Android version 7.1.1) (for other phones please check) is fully operational even when the phone is locked.
More precisely, if a stranger pushes the power button he has access to your volume button even if his fingerprint isn't recognized by the phone. Unfortunately, by default the volume button is linked to the Ring and notification volume and therefore, this stranger could decrease your ringing volume to zero even when the phone is locked. If you know a way to either:
i) link the volume button to the Media Volume instead of the Ring and notification volume; or
ii) completely disable the phone volume button when the phone is locked
please let me know.
Thank you in advance.

[baberkhan]

if your phone is under warranty get it checked from sony center or  take it to some authorized mobile technician, sometimes dirt may cause volume button failure or dead.

[Strampke]

Always look up the bright side of life.

This behaviour is by intent and has always been like that.

Up till Android version 8 Oreo you could silence it and even set it to 'do not disturb'by just pushing the volume button.

Very useful in a meeting, in church or whenever you do not want to be disturbed.

The volume down option is still there in Android 9 Pie, however the 'do not disturb' option by just long-pressing has been abandoned in Pie.

(another example of how software developers sometimes live a ine in their own hemisphere, not being aware of normal human beings' expectations)