title: "Android library projects cannot be launched"?
body: <p>Now I am totally confused by this error message: <strong>Android library projects cannot be launched.</strong> </p>
  
  <p>I carefully checked the build path and library, everything seems "OK", and there is no error on Problems view, however, when I tried to run my application as an Android project, it failed and showed that message.</p>
  
  <p>Any explanation for why it's happening is appreciated!</p>