Android Stack

There are 5 layers in the Android programming stack. Since the foundation of Android is Linux, the Linux kernel is the first stack.

Linux Kernel Layer

The folks who developed Android found Linux is:

• proven
• stable
• and secure

Linux has a great memory and process management scheme in addition Linux has a permission based security model that Android took.

In the Linux Kernel Layer stack you will find the software for the memory management, process management, and power management. This is also where the drivers for basic components like are kept:

Basic Components Lis:

• camera
• display
• WiFi
• Bluetooth
• Flash memory and more …

Libraries Layer

Most of the code is written in native code. Native code is either C or C++. These are fast executing computational routines most of the time.

Android rewrote libc (standard C library) so that it is optimized for embedded use.

In this layer there are also:

• SSL modules
• SQLLite modules
• Media Framework
• Webkit, etc…

SQLite is needed for contacts and apps.

Media framework supports media file formats.

Webkit is used like the browser basic engine.

The Run-Time Layer

Has 2 parts:

• The core libraries
• Android Runtime

Core libraries contain core classes that are in the android.jar file in your SDK.

Android Runtime (ART) (Android 5+) replaced Dalvik for improved application performance and battery usage.

Dalvik is a discontinued virtual machine. It was present before Android 5.

Application Framework

These are all Java layers representing the core platform services:

• Location Manager
• Telephony Manager
• Resource manager
• Notification Manager
• Activity Manager

Location Manager is to access the GPS. Telephony Manager interacts with the underlying Radio interface layer. Resource Manager will load images and strings. Notification Manager will add messages to the status bar. Activity Manager that handles the life-cycle, etc.

Application Layer

This is where core apps:

• Phone,
• Web Browser
• Contacts

and third party apps live.

Third party apps:

• Facebook
• YouTube
• Twitter
• Instagram
• TikTok

Android phones use the same API for both core apps and third party apps.