APK Detailed Explanation

APK is the abbreviation of Android Package, which is the Android installation package (apk). APK is a file format similar to Symbian Sis or Sisx. By directly transferring the APK file to an Android emulator or Android phone for execution, it can be installed. Like sis files, apk files package the projects compiled by the Android SDK into an installation program file in apk format. Actually, APK files are in zip format, but the extension is changed to apk. After unzipping with UnZip, you can see the Dex file. Dex stands for Dalvik VM Executable, which is the Android Dalvik executable program, not Java ME bytecode but Dalvik bytecode. When Android runs a program, it first needs to unzip it, then directly executes it similar to Symbian, which is different from PE files in Windows Mobile.

1. META-INF\ (Note: commonly seen in Jar files);
2. res\ (Note: directory for storing resource files);
3. AndroidManifest.xml (Note: global configuration file for the program);
4. classes.dex (Note: Dalvik bytecode);
5. resources.arsc (Note: compiled binary resource files).

Android is a Java-based development environment. It is a development language very similar to widely accepted Java and much easier than C, which sets a standard for mobile development. Google has also done an excellent job in writing API documentation and providing sample code.

• Getting the SDK: Download and install Android SDK [Software Development Kit], which mainly includes the core library files, an emulator, development tools, and some example sample files. It is recommended to use Eclipse and the Android Eclipse extension. If you only use Android, the Eclipse IDE is sufficient, but if it is your first time developing Java applications, it is recommended to download the full Java SE Development Kit (JDK) because it includes the tools needed to sign applications.