Android contains a great support for interacting with different web services. This tutorial shows how to make a basic GET request to a web server and read the returned contents.
This tutorial shows how to use Android AsyncTask class to run jobs in background threads. All long running jobs need to run in a background thread so that they won't lock up the UI and create an Application Not Responding dialog.
This tutorials shows how to show information to the user with Android Toast. Toast draws a small box to the screen with defined for short period of time. It is usefult for showing acknowledgements and other small info tidbits to the user.
This tutorial shows how to use RadioButton widgets on Android.
This page contains a simple tutorial on how to use the Android Spinner component. The Android Spinner component is the UI element which is usually know as dropdown list.