Now that you know you're ready to be an Android developer, grab your computer and get cracking on installing the tools and frameworks necessary to build your first blockbuster application.
Be aware that the full Android source code is open source, which means that it's not only free to use, but also free to modify. If you want to download the Android source code and create a new version of Android, you're free to do so. Check the Android Git repository. You can also download the source code at http://source.android.com.
Sometimes when you're developing an Android application, you may want to use a resource from the core Android system, an icon for a Settings menu option, for example. By accessing the Android source code, you can browse the various resources and download the resources you need for your project. Having access to the source code also enables you to dig in and see exactly how Android does what it does.
You can visualize the Android source code as a system of discrete layers, each built upon the other. These layers include the following (see Figure 4-1):
Android was created on top ...