App Inventor is perhaps the fastest and easiest way to develop custom Android applications. App Inventor uses a graphical programming model in a cloud-based development system. Sounds complicated, but its not at all. It’s easy.
App Inventor 2 is a significant update to version 1.
Application user interfaces are constructed using a WYSIWYG drag and drop style interface (similar to many such UI designers). Components are added, properties are edited.
Switch to the “Blocks” view and behaviors are attached to events by assembling program blocks that look like this:
Use of App Inventor 2 is presently free (its run by MIT) and uses a Google account for log in. Apps under development can be run in an emulator on your computer, or loaded into your actual Android phone using a Wi-Fi link, a USB connection, downloaded from a web site URL, or download the .apk file to your computer for transfer to your Android phone (USB or email it to your phone).
App Inventor was originally started by Google. MIT later took the project over and has made some very nice improvements to the original.
Can you do everything you would want to do in an app? No, but it is pretty amazing how much you can do in App Inventor. In some cases, you could implement much of your app in App Inventor, and then special custom code that cannot be done can be written as a separate activity. Your App Inventor code can then launch your code to perform the required functions.