Since we will use Android emulator as one of the virtual hardware platforms, we need to use one particular Android version throughout this book. At the time of writing, the latest Android version is Android 7 (Nougat). We will use Android 7 throughout the book. I started work on this book with Android 6, so the source code for Android 6 is also available in my GitHub repository at https://github.com/shugaoye.

From the first release to Android 7, both the development environment and the AOSP source code have been changed a lot. We will have a brief look at various Android versions first before we talk about the development environment setup.

To set up the AOSP build environment, there are two things that you need to pay special attention to the host environment and Java SDK. Even though the recommended host environment is Ubuntu running on Intel architecture, the hardware architecture...

Ideally, if you have an AOSP build environment, you can build everything including Android SDK from scratch. However, it is much more convenient to have an Android SDK installation to help with virtual device creation or running emulator images.

You can always download the latest Android SDK from the following website:

https://developer.android.com/index.html

The host environment that we use in this book is Ubuntu 14.04. Download the Android SDK for Linux and decompress it to a folder in your Home directory.

The tools in Android SDK have been changed since API level 25. You may use an older version of Android SDK or the latest Android SDK so I gave the instructions for both cases here.

In order to create our own Android system, we have to set up the AOSP build environment and build our own AOSP target for the Android emulator. Since Android is under rapid development, the build process and environment setup can change from time to time. You can always refer to Google's website for the latest information, https://source.android.com/source/building.html.

While the Google website and other sources can give general guidelines and procedures about the AOSP build, in this section we will look specifically at how to build AOSP for Android emulator image for API level 25.

Since we want to set up a build environment for API level 25, you can refer to the table of AOSP...

It usually takes a very long time to download the AOSP source code. After you have downloaded the AOSP source code, you have actually downloaded a specific version of the AOSP source code from the remote repository. You may have to test different configurations or versions in your development work. It is a very time-consuming task to switch to a different version or create a new copy of the AOSP source code.

In this book, we will use the AOSP source code as the base for our development. To reuse some of the existing open source projects that are not included in AOSP, we have to modify the repo manifest from time to time. This involves changing the repo configuration. To work more efficiently, we can use a local mirror. It can save a lot of time to create a local mirror instead of downloading source code from remote repositories for all configuration changes. It may take hours...

In this chapter, we set up the environment for SDK and AOSP. We built the Android emulator images for AOSP. We also tested and compared the Android images in Android SDK and AOSP. All these steps are necessary before we continue exploring how to create our own Android system later. We also spent some time discussing how to set up our own repo mirror. This tip can help us later, when we start to create projects from multiple open source projects. In the next chapter, we will start to explore the architecture of Android. We will look into the details of layers related to the porting and customization of the Android system.