Open-source, Linux-based OS optimized for battery-powered, low-memory devices with access to various interfaces
Versions: name and API version (eg. Android 12 supports both API 31 and API 32)
Linux kernel services
Android automatically manages the process lifecycle and interprocess communication, file and network I/O, device drivers, …
Security management: apps run in sandboxes, with permissions given by the user
Power management: screen dimming, process killing, JobScheduler API
Native libraries
- System C library
- Surface manager (composing windows), OpenGL (3D graphics)
- OpenMAX, Media Framework (audio / video / image processing)
- SQLite (relational database engine)
- Webkit (browser engine)
Android runtime
Compilation process:
- programmer Java/Kotlin source
- ==javac/kotlinc Java bytecode/class files==
- ==Proguard obfuscated Java bytecode/class files==
- ==DX DEX bytecode file==
- ==Zip .apk file (resources + code)==
- ==dex2out .elf file (readable to hardware)==
Process VM - compilation of .apk to native machine code:
- Dalvik (until 4.4 KitKat): trace-based just-in-time compilation (saving storage space, but lower performance)
- Android Runtime - ART (from 5.0 Lollypop): ahead-of-time compilation
Gradle: Automated build system, dependency manager, APK signing, ProGuard support
Application framework
- Package manager: manage installed applications
- Window manager: connect view to activity’s window
- Content provider: manage inter-application data sharing access
- Location manager / Google Play Location Services: provide location information
- Notification manager: manage sound, vibration, LED flash and content of notifications
- Resource manager: manage (programmatically accessible) application resources
- Activity manager: manage application lifecycle and application stack navigation
- View system: build application UI from a layout definition, slowly deprecated for Jetpack Compose
System applications
Handling certain Intents