It appears every time you make or receive a call. It displays the contact name, the duration, the mute button, and the dreaded red "end" icon. But behind those familiar touch targets lies one of the most complex, security-sensitive, and historically problematic modules in the Android Open Source Project (AOSP): .
Here is a deep dive into the architecture, evolution, and hidden intelligence of the Android call screen. In technical terms, InCallUI is a system application ( com.android.dialer.incallui ) responsible for the in-call screen. It is not the dialer. While the Dialer app handles number input and search, the InCallUI takes over the moment the telephony stack answers a ringing event. android incallui
Since Android 6.0, any dialer app can implement the InCallService and replace the default call screen. This is how apps like Truecaller or Simple Dialer work. 3. Critical Feature #1: The Proximity Sensor Dance InCallUI must handle a hardware nightmare: the proximity sensor. A bug here causes "black screen of death" (can’t hang up) or "pocket dialing" (screen on during call). It appears every time you make or receive a call