Incoming call notification - Android/iOS

I am developing a voip based phone call app specially for video conferencing type calls. Everything works via normal push notifications.

how do I show incoming call screen with sound e.g.

I am trying to implement - https://developer.android.com/guide/topics/connectivity/telecom/selfManaged not sure if I am in the right direction.

Note: I don't want to interrupt/intercept normal phone calls.

I have managed to implement this using combination of push notification, broadcast receiver, alarm service, setting window flags on activity with "FullScreenIntent".

• "OnMessageReceived" set an alarm for x seconds (500ms) with Broadcast receiver
• in receiver setup MainActivity intent and set flags "NewTask" and "frombackground"
• In MainActivity - override "OnNewIntent", set the window flags

Window.AddFlags(WindowManagerFlags.KeepScreenOn); Window.AddFlags(WindowManagerFlags.DismissKeyguard); Window.AddFlags(WindowManagerFlags.ShowWhenLocked); Window.AddFlags(WindowManagerFlags.TurnScreenOn); Window.AddFlags(WindowManagerFlags.Fullscreen);

this will open the app in fullscreen and can be routed to appropriate page for custom UI