Basics: Android Applications

Applications in Android are a bit different from what you may be used to in the desktop and server environments. The differences are driven by a few key concepts unique to the mobile phone environment and unique to Google’s intentions for Android.

Limited resources

Mobile phones today are very powerful handheld computers, but they are still limited. The fundamental limitation of a mobile device is battery capacity. Every clock tick of the processor, every refresh of memory, every backlit pixel on the user’s screen takes energy from the battery. Battery size is limited, and users don’t like frequent battery charging. As a result, the computing resources are limited— clock rates are in the hundreds of MHz, memory is at best a few gigabytes, data storage is at best a few tens of gigabytes.

Mobile mashups

In the desktop Internet world, mashups make it very easy to create new applications by reusing the data and user interface elements provided by existing applications. Google Maps is a great example: you can easily create a web-based application that incorporates maps, satellite imagery, and traffic updates using just a few lines of JavaScript on your own web page. Android extends that concept to the mobile phone. In other mobile environments, applications are separate, and with the exception of browser-based applications, you are expected to code your applications separately from the other applications that are running on the handset. In Android you can easily create new applications that incorporate existing applications.

Interchangeable applications

In other mobile software environments, applications are coded to access data from specific data providers. If you need to send an email from a Windows Mobile application, for example, you code explicit references to Pocket Outlook’s email interface, and send the email that way. But what if the user wants to use another email client?

Android incorporates a fundamental mechanism (Intents) that is independent of specific application implementations. In an Android application, you don’t say you want to send email through a specific application; instead, you say you want to send an email through whatever application is available. The operating system takes care of figuring out what application can send emails, starts that application if needed, and connects your request so the email can be sent. The user can substitute different browsers, different MP3 players, or different email clients at will, and Android adapts automatically.

That is why android sounds exciting and has endless features to play with.