Android powers hundreds of millions of mobile devices in more than 190 countries around the world. It's the largest installed base of any mobile platform and growing fast—every day another million users power up their Android devices for the first time and start looking for apps, games, and other digital content. Android gives you a world-class platform for creating apps and games for Android users everywhere, as well as an open marketplace for distributing to them instantly.
Before installing the Android SDK, you must agree to the following terms and conditions. This is the Android Software Development Kit License Agreement 1. Introduction 1.1 The Android Software Development Kit (referred to in this License Agreement as the "SDK" and specifically including the Android system files, packaged APIs, and Google APIs add-ons) is licensed to you subject to the terms of this License Agreement. This License Agreement forms a legally binding contract between you and Google in relation to your use of the SDK. 1.2 "Android" means the Android software stack for devices, as made available under the Android Open Source Project, which is located at the following URL: http://source.android.com/, as updated from time to time. 1.3 "Google" means Google Inc., a Delaware corporation with principal place of business at 1600 Amphitheatre Parkway, Mountain View, CA 94043, United States.
You should have already downloaded the Android SDK Tools. (If you downloaded the ADT Bundle, you should instead read Setting Up the ADT Bundle.) The SDK Tools package is not the complete SDK environment.
Terms An Activity is an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map. Each activity is given a window in which to draw its user interface.
Web Apps Figure 1. You can make your web content available to users in two ways: in a traditional web browser and in an Android application, by including a WebView in the layout. There are essentially two ways to deliver an application on Android: as a client-side application (developed using the Android SDK and installed on user devices in an APK) or as a web application (developed using web standards and accessed through a web browser—there's nothing to install on user devices).
Android is designed to run on many different types of devices, from phones to tablets and televisions. As a developer, the range of devices provides a huge potential audience for your app. In order for your app to be successful on all these devices, it should tolerate some feature variability and provide a flexible user interface that adapts to different screen configurations. To facilitate your effort toward that goal, Android provides a dynamic app framework in which you can provide configuration-specific app resources in static files (such as different XML layouts for different screen sizes). Android then loads the appropriate resources based on the current device configuration. Best Practices
Welcome to Training for Android developers.