Android Learning Path (i)

This blog is the second line of code for the study notes, most of which are all taken from the second line of code.

(i) Android system architecture

Broadly divided into: Linux kernel layer, System runtime layer, application framework layer and application layer.

1. Linux kernel layer

The Android system is based on the Linux kernel, providing low-level drivers for various hardware devices, such as display drivers, audio drivers, camera drivers, bluetooth drivers, Wi-Fi drivers, power management, and more.

2. System Runtime Layer

Provide Android with the same feature support as you would with a C + + library. such as SQLite provides database support, opengl| The ES Library provides 3D drawing support, and WebKit provides browser kernel support. Also on this level, there is the Android runtime library, which mainly provides core libraries that allow developers to write Android apps in the Java language. The Android Runtime library also contains the Dalvik virtual machine (5.0 system changed to the Art runtime environment), it is each Android application can run in a separate process, and has its own Dalvik virtual machine strength. Compared to the Java Virtual machine, Dalvik is specifically tailored for mobile set-up, which is optimized for mobile memory CPU performance.

(The mechanism of ART is different from Dalvik.) Under Dalvik, every time the application is run, the bytecode needs to be converted to machine code via an instant compiler, which slows down the efficiency of the application, while in the art environment, when the application is first installed, bytecode is pre-compiled into machine code, making it a true native application. This process is called precompilation (aot,ahead-of-time). In this case, the startup (first time) and execution of the application will become faster. ）

3. Application Framework Layer

Some of the core applications that can be used to build an application are those that use these APIs, and developers can build their own applications by using these APIs. api,android

4. Application Layer

The app belongs to this layer.

(ii) version

The Google I/O Conference, Android5.0, replaces the Dalvik virtual machine with the Art runtime environment. The concept of material design is proposed to optimize the application interface. In addition to the launch, Android wear,android auto,android TV. In order to enter wearable devices, automobiles, televisions and so on.

Google I/O Android 6.0, join the Run-time permissions feature

Google I/O Android 7.0, add the Multi-window mode feature.

There are now 8.0

Android Learning Path (i)