I had the same problem. Try
- Right click on your project
- Go to properties
- Click the Android section
- Select a different target api (assuming one is already selected, as mine was – otherwise, select the one you want and jump to step 9)
- Click OK
- Do steps 1-3 again
- Select your original target api
- Click OK
- Clean and build your project
Worked for me, anyway.
Derived the solution from:
“Unable to get system library for project” after I upgraded to Android SDK 2.3 and ADT 8.0