Disclaimer
No warranty
Call Prefix Filter is an individual's amateur project. The app does not offer any warranty.
Android landscape
v1.x.x and v2.0.x
The app calls the internal Telephony API to drop a call. A multitude of phone vendor customize their Android firmware in different ways. There is no guarantee that the app works in all the variants. In fact, it is found that some phones work better than the others.
The early releases can no longer drops a call at the Android 8.0 emulator. Some phone vendors still tailor their Android Oreo firmware to support older call blocker. Nevertheless, the support for backwards compatibility vanishes with time. The app does not work on most phones running on Android 10 or newer.
v3.x.x
The app is migrated to the CallSceeningService API, which is introduced in Android 7.0. The app requires Android 10 or newer, which facilitates a call screener without being a dialer.
Test environment
v3.x.x
The app works well in the following Android Emulator instances.
Android 12.1, x86_64 platform.
Android 11.0, x86 platform.
Android 10.0, x86 platform.
v1.x.x and v2.0.x
The app works well in several mobile phones.
Android 6.0, arm platform.
Android 7.0, arm64 platform.
Android 8.0, arm64 platform.
For privacy reason, the specifications of the phones are not disclosed.
The app works well in the following Android Emulator instances.
Android 7.0, x86 platform.
Android 6.0, x86_64 platform.
Android 5.0, x86_64 platform.
Android 4.1, x86 platform.
Android 4.0, arm platform.
Android 2.3, arm platform.