Updated Android Studio to 0.2.6 you can run into this error:
“Error: Default activity not found”, almost every line was red and some other irrelevant error. Nothing was changed in the project, only did the update from 0.2.5 to 0.2.6.
Do the following to fix the problem:
Build -> Rebuild Project and then restart Android Studio.
Thanks to #1 mike…@gmail.com
Source: Issue 59435 at https://code.google.com/p/android/issues/detail?id=59435