1. The development history of Android
- In 2003, the Android operating system was developed by Andy Rubin's Android company
- In 2005, Google acquired the Android company
- In 2007, Android was open sourced
- In 2008, the Android 1.0 version was released, and the first Android phone HTC T-Mobile G1 came out
2. Features of Android
Android is a free and open source operating system based on Linux.
Therefore, the biggest feature of Android is that it is open source, free, and customizable .
Free open source is a double-edged sword, attracting many developers into the field of Android development and promoting the rapid development of Android; but it also brings a serious problem: fragmentation .
Fragmentation includes: screen fragmentation and system fragmentation . We need to take into account the fragmentation problem to adapt when developing, and then carefully explore this piece in the future.
3. Android API level
4. Android system architecture
1. Linux Kernel Layer
The Android system is based on Linux. This layer provides various underlying drivers for various hardware of Android devices, such as audio drivers, camera drivers, Bluetooth drivers, etc.
2. System runtime layer
Libraries: C/C++ libraries that provide some feature support for the Android system, such as SQLite library provides database support, Webkit library provides browser kernel support, etc.
Core library: allows developers to develop Android applications using the Java language
Virtual machine: Dalvik virtual machine (changed to ART operating environment after 5.0) is specially customized for mobile devices. It is optimized for limited memory and CPU. It makes each Android application run in an independent process. And has its own instance of Dalvik. Dalvik is compiled at runtime, compiled when ART is installed, and does not need to be compiled when running later
3. Application Framework Layer
Mainly some of Android's own core APIs
4. Application layer
The applications we develop, the contacts and desktops that come with the system are all in this layer