Use the Android software development kit (SDK) to develop apps that take advantage of the Android operating system and UI. The SDK includes a comprehensive set of development tools including a debugger, software libraries of prewritten code, a device emulator, documentation, sample code, and tutorials. Use these tools to create apps that look great and take advantage of the hardware capabilities available on each device.
To develop apps using the SDK, use the Java programming language for developing the app and Extensible Markup Language (XML) files for describing data resources. By writing the code in Java and creating a single app binary, you will have an app that can run on both phone and tablet form factors. You can declare your UI in lightweight sets of XML resources, one set for parts of the UI that are common to all form factors, and other sets for features specific to phones or tablets. At runtime, Android applies the correct resource sets based on its screen size, density, locale, and so on. To help you develop your apps efficiently, Google offers a full Java Integrated Development Environment (IDE) called Android Studio, with advanced features for developing, debugging, and packaging Android apps. Using Android Studio, you can develop on any available Android device, or create virtual devices that emulate any hardware configuration. Android provides a rich development architecture. You don’t need to know much about the components of this architecture, but it is useful to know what is available in the system for your app to use.
The following diagram shows the major components of the Android stack — the operating system and development architecture.
1. Apps: Your apps live at this level, along with core system apps for email, SMS messaging, calendars, Internet browsing, or contacts.
2. Java API Framework: All features of Android are available to developers through application programming interfaces (APIs) written in the Java language.
You don't need to know the details of all of the APIs to learn how to develop Android apps, but you can learn more about the following APIs, which are useful for creating apps: View System used to build an app's UI, including lists, buttons, and menus. Resource Manager used to access to non-code resources such as localized strings, graphics, and layout files. Notification Manager used to display custom alerts in the status bar.
Activity Manager that manages the lifecycle of apps. Content Providers that enable apps to access data from other apps.
1.0: Introduction to Android 8 All framework APIs that Android system apps use. 3. Libraries and Android Runtime: Each app runs in its own process and with its own instance of the Android Runtime, which enables multiple virtual machines on low-memory devices. Android also includes a set of core runtime libraries that provide most of the functionality of the Java programming language, including some Java 8 language features that the Java API framework uses. Many core Android system components and services are built from native code that requires native libraries written in C and C++. These native libraries are available to apps through the Java API framework. 4. Hardware Abstraction Layer (HAL): This layer provides standard interfaces that expose device hardware capabilities to the higher-level Java API framework. The HAL consists of multiple library modules, each of which implements an interface for a specific type of hardware components, such as the camera or Bluetooth module. 5. Linux Kernel: The foundation of the Android platform is the Linux kernel. The above layers rely on the Linux kernel for underlying functionalities such as threading and low-level memory management. Using a Linux kernel enables Android to take advantage of key security features and allows device manufacturers to develop hardware drivers for a well-known kernel.
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