Basic working of android application framework

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Android is a vast software system and it has been developed in a modular manner by using layers for it’s specific functionality on top of the Linux kernel to speed up development and still be open source.

Various layers of Android are shown in the image below

Linux Kernel – The lowest layer of the Android framework is the Linux kernel for low level hardware interfaces.

DVM / Libraries – Java programming language, is used for developing Android applications which are executed on a virtual machine (VM) instead of JVM and it is the Dalvik Virtual Machine (DVM). Every Android application runs in an instance of the DVM.

Applications – They are Android applications which are either custom developed or are provided with Android.

The layering is illustrated as

Android Application Framework – An Android application is actually a package of different components and each tasked for specific aim. It is not a executable as in case of Windows and has the following

Intents – It is usually an ‘action’ instruction and is a Java package name prefixed as ‘action.COMMAND_NAME.’. IThey are actually events to which the application will reply to.

Services – They run in background and persist even though might not always be in top of screen.

BroadcastReceivers – They alert applications of events in the device.

Activity – It is the part of application with which user interacts with.

ContentProviders – They enable data sharing amongst Android applications