Google Android as a mobile development platformT-110.7111 Internet Technologies for Mobile ComputingOlli Mäkinen

Google Android

• Google’s own mobile operating system based on Linux• Open source with all primary components published• Google still has some closed-source applications

running on top (such as GPS navigation and the application store)

• Manufacturers are open to make their own adjustments to the OS without the requirement of publishing them as open source

Android System Architecture

Source: Google

Third Party Software

• Android spawns a Dalvik virtual machine for each application, including third party ones

• This enables strong control of the application’s behaviour and also helps with misbehaving applications

• Multi-tasking is available• An application framework provides a vast range of components that

can be used in the applications• Third parties can also install additional components that can be used

in other software• Signing is mandatory for distribution of the applications (self-signing

is possible too)• Android Market is available quite openly ($25 one-time fee plus a

30% royalty for Google)

Android Development

• Java based, but is not compliant with J2ME (Micro Edition) or J2SE (Standard Edition)

• Hardware features are available through Java APIs• SDK is available on Windows, OS X and Linux

machines• The SDK includes an emulator for different Android

device versions (up to 2.1 currently)• Plug-in (Android Development Tools, ADT) available for

Eclipse• Debugging is easy with the plug-in

Application Framework

• View System– Contains GUI elements, with XML-based layouts

• Content Providers– Provides interchangeable data between applications, such as contact

lists

• Resource Manager– Separate data storage for language files, graphics and layout data

• Notification Manager– Allows applications to add alerts, such as status bar messages,

sound or vibration

• Activity Manager– Controls the lifecycle of the applications

A Typical Android Application

• Activity– Java code– At least one needs to be specified– Each has its own view(s)

• Resources– Text strings, image files or other data

• Views– XML-based GUI– A view is one component, a view group contains many views– Several different layout options = view groups– Standardized components (buttons, input fields) = views

• R class– Generated based on the GUI and resources

• Event listeners for the components created into the Activity• A menu can be added for settings, created automatically

Links

• http://www.xtensivearts.com/2009/07/27/episode-4-checkboxes-complex-layouts/

• http://developer.android.com/sdk/index.html