Application Fundamentals. Android apps are written in the Java programming language.
The Android SDK tools compile your code—along with any data and resource files—into an APK: an Android package, which is an archive file with an .apk suffix. One APK file contains all the contents of an Android app and is the file that Android-powered devices use to install the app. Once installed on a device, each Android app lives in its own security sandbox: The Android operating system is a multi-user Linux system in which each app is a different user.
Developing on a Device. When building a mobile application, it's important that you always test your application on a real device before releasing it to users.
This page describes how to set up your development environment and Android-powered device for testing and debugging on the device. You can use any Android-powered device as an environment for running, debugging, and testing your applications. The tools included in the SDK make it easy to install and run your application on the device each time you compile. You can install your application on the device directly from Eclipse or from the command line with ADB. How to create android applications for tablets? With the new 2.3 SDK, we get the opportunity to develop android for tablets.
(At least, with the Galaxy Tab Addon). When starting a new tablet emulator, first we need to set the "Scale display to real size" option. This helps to set the tablet's size, to our screen size.