Google Android SDK

Android software development is the process of creating new applications for the operating system of Android. Applications are created using Java programming language. Android SDK [software development kit] includes a comprehensive set of applications such as libraries, debuggers, documentation, sample code, handset emulator based on QEMU and tutorials for Android. It works on Microsoft Windows XP and later, Mac OS X 10.5.8 or later for Mac platforms. Developers can use any text editor to edit XML and Java files, use command line tools of Apache Ant and Java Development Kit to create, debug and build applications and control devices attached to your Android such as remote installation of a software package and triggering a reboot. Applications for Android are packaged in APK file format. The APK package stores DEX files called Dalvik executables which are compilations of byte code files. Android applications are made of one or more components such as content providers, services, activities and broadcast receivers. Every component has its own role in the overall behavior of the application, and be accessed or executed individually by the application or even other applications [depending on permit availability].

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Google Android SDK for Linux

Android SDK is the program that provides you the developer tools and API libraries you need to test, debug and build applications for Android. Applications for Android are written in Java programming language. Android SDK tools compile the program code along with resource files and any other data into an archive of files with APK format known as the Android package. Android SDK for Linux systems has been tested on Lucid Lynx and Ubuntu Linux. It requires GNU C Library [glic] 2.7 or later. It requires version 8.04 on Ubuntu Linux. 64-bit distributions should be able to run 32-bit applications. Some Linux distributions may support GNU Compiler for Java [gcj] or JDK 1.4. Both are not supported by development for Android. All the codes in an APK file are considered one program, and it is the file used by Android-powered devices to install the program. Once installed, every application lives on its own security sandbox. The operating system of Android is a multiuser Linux program wherein every application is considered a different user. The system assigns a unique Linux user ID to each application [unknown to the user and used by the system alone]. The system sets a permit for all files in the application so that only the corresponding user ID assigned to that application can access them. This means that an application runs independent of other applications because each application has its own VM [virtual machine]. Every program, by default, operates its own Linux process. Android begins the operation when one of the application’s components has to be executed, then stops the operation when no longer needed or when system has to recover memory for other programs. This is Android’s “principle of least privilege”. The application can only access components that will do the job needed and nothing else. This provides system security as the application cannot access components without system permit. But an application can share data with other applications and access system services through a couple of ways. Two applications can be possibly arranged to share a Linux user ID for them to access each other’s components. Applications sharing the same ID must run with the same Linux process, share the same virtual machine [VM], and have the same certificate to save system resources. Another way is for the application to request for a permit to access device data like SMS messages, contacts, SD card or mountable storage, camera, etc. The user must grant all application permits during installation time.

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