Right now I'm working on a video chat project. I've made it so that when a call comes in, you receive a push notification informing you of the call. The notification produces a ringtone when it's delivered. On android 9 and above, the ringtone volume doesn't change when you try to change it through the volume buttons. I found some android documentation that states this is intentional.
https://developer.android.com/guide/topics/media-apps/volume-and-earphones
The thing is, apps like Facebook messenger some how allow you to change the ringtone volume on android 9 and above devices. How are they accomplishing this?