title: When exactly is the NFC Service deactivated?
body: <p>I am wondering when exactly the NFC Service is started and stopped.
  The source code for android 4.0.3 seems to state that the polling is dependent on a single constant (located in NfcService.java)</p>
  
  <pre><code>/** minimum screen state that enables NFC polling (discovery) */
  static final int POLLING_MODE = SCREEN_STATE_ON_UNLOCKED;
  </code></pre>
  
  <p>I would interpret this as "the screen light is on, therefore the nfc service is active".
  BUT when the screen is locked, a NFC Tag wont be recognized, altough the screen is lit.</p>
  
  <p>So I am curious: Is the NFC Service already deactivated when the lock screen appears, or is it still running but not processing the Tags?</p>