Page 66 "TRY IT OUT" the modify the "secondactivity.xml" file name is incorrect and such a filename does not exist. The correct filename is "activity_second.xml".
Page 73, Para 6, "import android.Activity;" should be "import android.app.Activity;"
Thank you for your post!
I'll send this to the editor for review. What's the ISBN of your book?
Have a nice evening!