android: turn off screen when close to face

If you are allowed to look at open source code without causing yourself problems, check the source of the Android Phone Application. Specifically src/com/android/phone/PhoneApp.java and src/com/android/phone/InCallScreen.java.

From src/com/android/phone/PhoneApp.java:

 //Around line 519
 // Wake lock used to control proximity sensor behavior.
 if ((pm.getSupportedWakeLockFlags()
          & PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK) != 0x0) {
     mProximityWakeLock = pm.newWakeLock(
         PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK,
         LOG_TAG);
 }

 ....
// Around line 1334
if (((state == Phone.State.OFFHOOK) || mBeginningCall)&& !screenOnImmediately) {
  // Phone is in use!  Arrange for the screen to turn off
  // automatically when the sensor detects a close object.
  if (!mProximityWakeLock.isHeld()) {
      if (DBG) Log.d(LOG_TAG, "updateProximitySensorMode: acquiring...");
      mProximityWakeLock.acquire();
  } else {
      if (VDBG) Log.d(LOG_TAG, "updateProximitySensorMode: lock already held.");
  }
} else {
  // Phone is either idle, or ringing.  We don't want any
  // special proximity sensor behavior in either case.
  if (mProximityWakeLock.isHeld()) {
    if (DBG) Log.d(LOG_TAG, "updateProximitySensorMode: releasing...");
    // Wait until user has moved the phone away from his head if we are
    // releasing due to the phone call ending.
    // Qtherwise, turn screen on immediately
    int flags =
        (screenOnImmediately ? 0 : PowerManager.WAIT_FOR_PROXIMITY_NEGATIVE);
    mProximityWakeLock.release(flags);
  }
}

Additionally, if you look at the code for the PowerManager class, PROXIMITY_SCREEN_OFF_WAKE_LOCK is documented (but hidden) and should do what you want ( I am not sure which API level this works for, however ) — but not in the table for some reason.

/**
 * Wake lock that turns the screen off when the proximity sensor activates.
 * Since not all devices have proximity sensors, use
 * {@link #getSupportedWakeLockFlags() getSupportedWakeLockFlags()} to determine if
 * this wake lock mode is supported.
 *
 * {@hide}
 */
public static final int PROXIMITY_SCREEN_OFF_WAKE_LOCK = WAKE_BIT_PROXIMITY_SCREEN_OFF;

If you aren’t afraid of using a potential undocumented feature, it should do exactly what you need.