Trying to overlay a Dialog on top of the system InCallUI. This never works reliably due to SYSTEM_ALERT_WINDOW restrictions and the fact that the system InCallUI has the highest priority ( TYPE_APPLICATION_OVERLAY is lower than TYPE_PHONE ).
Now, your Android tablet can show an InCallUI for a call active on your phone. This is implemented via a new InCallService extension that proxies touch events (mute, speaker) back to the phone over Bluetooth LE. incallui
The InCallUI activity requires an absurdly fast start-up time. Telecom starts a "warm-up" process pre-emptively. If your InCallActivity takes longer than ~200ms to inflate its layout or bind to InCallService , the system times out. The call connects, but the UI never appears. Trying to overlay a Dialog on top of the system InCallUI