I open an older project which has a normal Android 2.2 external library registered. I want to use Google maps and I change the external library to Android 2.2 Google APIs. A
Make sure you only have lower caps characters in the path to the file.
In IDEA 12 at least, Preferences > Schemas and DTDs, press the + to add External Schemas and DTDs, in the URI edit field add "http://schemas.android.com/apk/res/android", press OK to save. This was a little flaky, I had to do it twice, but it worked, the error is gone.
Try IDEA 10.5 EAP, it has improved Android support and easier SDK configuration. File | Invalidate caches may also help.
Unfortunatelly, I couldn't find the solution to this issue and, so far, the only way to solve is to create a new project with correct external libraries and to copy files into it.
You should maybe check the configuration of your modules. Be sure to mark the relevant folders as "Sources", "Test Sources" or "Excluded".
I had a namespace warning in res/anim/fade_in.xml
. When I marked the resource folder of my project as "Sources" as shown in the screenshot the namespace errors disappeared.