I've been trying to implement Google In-App Billing into one of my Android apps by following http://developer.android.com/training/in-app-billing/preparing-iab-app.html#GetSample
but I get the error that "IabHelper cannot be resolved to a type" after following the steps for an "Existing Project". I've added a picture as well.
Make sure you have followed step 3:
Add the helper classes from the /util directory of the TrivialDrive sample to your project. Remember to change the package name declarations in those files accordingly so that your project compiles correctly.
You need to copy all the classes under
com.example.android.trivialdrivesample.util and put them in your project.
IabHelper is one of them and seems to be what you are missing.