2. Android Studio

Android Studio is the official Integrated Development Environment (IDE) for Android app development, based on IntelliJ IDEA . On top of IntelliJ's powerful code editor and developer tools, Android Studio offers even more features that enhance your productivity when building Android apps, such as:

• A flexible Gradle-based build system
• A fast and feature-rich emulator
• A unified environment where you can develop for all Android devices
• Apply Changes to push code and resource changes to your running app without restarting your app
• Code templates and GitHub integration to help you build common app features and import sample code
• Extensive testing tools and frameworks
• Lint tools to catch performance, usability, version compatibility, and other problems
• C++ and NDK support
• Built-in support for Google Cloud Platform, making it easy to integrate Google Cloud Messaging and App Engine

Project structure

Each project in Android Studio contains one or more modules with source code files and resource files. Types of modules include:

• Android app modules
• Library modules
• Google App Engine modules

By default, Android Studio displays your project files in the Android project view, as shown in figure 1. This view is organized by modules to provide quick access to your project's key source files.

All the build files are visible at the top level under Gradle Scripts and each app module contains the following folders:

• manifests: Contains the AndroidManifest.xml file.
• java: Contains the Java source code files, including JUnit test code.
• res: Contains all non-code resources, such as XML layouts, UI strings, and bitmap images.

The Android project structure on disk differs from this flattened representation. To see the actual file structure of the project, select Project from the Project dropdown.

You can also customize the view of the project files to focus on specific aspects of your app development. For example, selecting the Problems view of your project displays links to the source files containing any recognized coding and syntax errors, such as a missing XML element closing tag in a layout file.

Gradle build system

Android Studio uses Gradle as the foundation of the build system, with more Android-specific capabilities provided by the Android plugin for Gradle. This build system runs as an integrated tool from the Android Studio menu, and independently from the command line. You can use the features of the build system to do the following:

• Customize, configure, and extend the build process.
• Create multiple APKs for your app, with different features using the same project and modules.
• Reuse code and resources across sourcesets.

By employing the flexibility of Gradle, you can achieve all of this without modifying your app's core source files. Android Studio build files are named build.gradle. They are plain text files that use Groovy syntax to configure the build with elements provided by the Android plugin for Gradle. Each project has one top-level build file for the entire project and separate module-level build files for each module. When you import an existing project, Android Studio automatically generates the necessary build files.

Build variants

The build system can help you create different versions of the same application from a single project. This is useful when you have both a free version and a paid version of your app, or if you want to distribute multiple APKs for different device configurations on Google Play.

Multiple APK support

Multiple APK support allows you to efficiently create multiple APKs based on screen density or ABI. For example, you can create separate APKs of an app for the hdpi and mdpi screen densities, while still considering them a single variant and allowing them to share test APK, javac, dx, and ProGuard settings.