The call to onActivityResult happens before onResume, actually (see the docs). Are you sure you’re actually starting the activity you wanted with startActivityForResult and that you’re setting the result of the invoked activity to RESULT_OK before returning a value to your activity? Try just putting a Log statement in your onActivityResult to log that value and make sure that gets hit. Also, where are you setting the value of the isLoggedIn preference? It seems like you should be setting that to true in your login activity before it returns anyways, but that’s clearly not happening.
Edit
The docs say:
You will receive this call immediately before onResume() when your activity is re-starting.