[android] Application Error - The connection to the server was unsuccessful. (file:///android_asset/www/index.html)

Another reason this error might occur is: there is no index.html in .../YourApp/www/ !

I just followed the ionic guide, and one of the steps is:

$ rm www/index.html

On iOS this is no problem as during the build the compiler takes some default HTML instead. However, when building for android, NO example index.html is used. Took me sometime to find out ("WHY does it work on iOS, but not on android...?)

Easy solution: create a index.html, save it under .../YourApp/www, rebuild ...et voila!