Book Image

Android System Programming

By : Roger Ye, Shen Liu
Book Image

Android System Programming

By: Roger Ye, Shen Liu

Overview of this book

Android system programming involves both hardware and software knowledge to work on system level programming. The developers need to use various techniques to debug the different components in the target devices. With all the challenges, you usually have a deep learning curve to master relevant knowledge in this area. This book will not only give you the key knowledge you need to understand Android system programming, but will also prepare you as you get hands-on with projects and gain debugging skills that you can use in your future projects. You will start by exploring the basic setup of AOSP, and building and testing an emulator image. In the first project, you will learn how to customize and extend the Android emulator. Then you’ll move on to the real challenge—building your own Android system on VirtualBox. You’ll see how to debug the init process, resolve the bootloader issue, and enable various hardware interfaces. When you have a complete system, you will learn how to patch and upgrade it through recovery. Throughout the book, you will get to know useful tips on how to integrate and reuse existing open source projects such as LineageOS (CyanogenMod), Android-x86, Xposed, and GApps in your own system.

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Table of Contents (15 chapters)
Preface
Preface
Virtual hardware platforms
Android version used in this book
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
Introduction to Android System Programming
Introduction to Android System Programming
What is system programming?
What is the scope of this book?
Overview of the Android system
The third-party open source projects derived from AOSP
Strategy of integration
Virtual hardware reference platforms
Summary
2
Setting Up the Development Environment
Setting Up the Development Environment
Summary of Android versions
Installing Android SDK and setting up an Android Virtual Device
The AOSP build environment and the Android emulator build
Creating your own repository mirror
Summary
3
Discovering Kernel, HAL, and Virtual Hardware
Discovering Kernel, HAL, and Virtual Hardware
What is inside the AOSP?
Android emulator HAL
Android emulator kernel and hardware
Summary
4
Customizing the Android Emulator
Customizing the Android Emulator
Why customize the Android emulator
Understanding build layers
Build variants
Creating a new x86emu device
Building and testing x86emu
Summary
5
Enabling the ARM Translator and Introducing Native Bridge
Enabling the ARM Translator and Introducing Native Bridge
Introducing Native Bridge
Integrating Houdini to the x86emu device
Building and testing
Summary
6
Debugging the Boot Up Process Using a Customized ramdisk
Debugging the Boot Up Process Using a Customized ramdisk
Analyzing the Android start up process
Source code and manifest changes
The Android-x86 start up process
Building x86emu with initrd.img
Creating a filesystem image
Kernel changes
Booting a disk image on the Android emulator
Summary
7
Enabling Wi-Fi on the Android Emulator
Enabling Wi-Fi on the Android Emulator
Wi-Fi on Android
Adding Wi-Fi to the emulator
Building the source code
Testing Wi-Fi on an emulator
Summary
8
Creating Your Own Device on VirtualBox
Creating Your Own Device on VirtualBox
HAL of x86vbox
Creating a new x86vbox device
Boot up process and device initialization
Summary
9
Booting Up x86vbox Using PXE/NFS
Booting Up x86vbox Using PXE/NFS
Setting up a PXE boot environment
Configuring and testing the PXE boot
NFS filesystem
Configuring the PXE boot menu
Summary
10
Enabling Graphics
Enabling Graphics
Introduction to the Android graphics architecture
Delving into graphics HAL
Graphics HAL of the Android emulator
Summary
11
Enabling VirtualBox-Specific Hardware Interfaces
Enabling VirtualBox-Specific Hardware Interfaces
OpenGL ES and graphics hardware initialization
Integrating VirtualBox Guest Additions
Summary
12
Introducing Recovery
Introducing Recovery
Recovery introduction
Analyzing recovery
Building recovery for x86vbox
Summary
13
Creating OTA Packages
Creating OTA Packages
What is inside an OTA package
Preparing an OTA package for x86vbox
Removing dependencies on /system
Building and testing
Summary
14
Customizing and Debugging Recovery
Customizing and Debugging Recovery
Debugging and testing native Android applications
Extending recovery and the updater
Supporting the third-party recovery packages
Summary

Strategy of integration

In the preceding sections, we talked about Android architecture, AOSP, and third-party open source projects for Android. The software industry has been there for decades. There are so many existing source codes that can be reused and the need to create something from scratch is very rare. The porting and customization for a new platform is basically art of integration.

In this book, we will use the AOSP source code as the foundation and try to build everything on top of it. However, we may not be able to rely on AOSP source code only. In fact, we want to demonstrate how to support a platform that is not supported by AOSP. How are we going to do this? Do we create something from scratch? The answer is no. We will demonstrate how we can integrate all existing projects together to create a new platform. That's the reason why we discuss third-party open source projects.

In our case, VirtualBox is not supported by AOSP and we are going to enable it using AOSP and Android-x86. We need to use projects from both AOSP and Android-x86 to build a system for VirtualBox. However, our goal is to create a new build system for VirtualBox with minimal changes to the AOSP source code tree. This is also the goal of many other projects based on AOSP.

Based on the previous understanding, we have four categories of projects in our integration process:

  • The original unmodified AOSP projects: In these kinds of projects, we will use AOSP projects without any changes.
  • The third-party projects: In this category, the projects are added by the third-party projects and are not part of AOSP, so there are no changes involved as well.
  • Projects modified by both AOSP and one of the third-party projects: This is complicated. We need to review the third-party changes and decide whether we want to include them in our system or not.
  • Projects modified by multiple open source projects and AOSP: This is the most complicated case that we should avoid to integrate or change.

It is very easy to understand that we should try to reuse projects in category 1 and 2 as much as possible. The challenges and major work will be in category 3, while we should try to avoid category 4 whenever possible.

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