code: public void acquireWakeLock() {
          if(mWakeLock == null) {
              PowerManager manager = (PowerManager) mContext.getSystemService(
                      Context.POWER_SERVICE);
              mWakeLock = manager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, mTag);
              mWakeLock.acquire();
              Log.d(mTag, "Wake lock acquired");
          } else {
              Log.d(mTag, "Already have a wake lock -- keeping it");
          }
      }
docs: Acquire a wake lock if we don't already have one.
  
  If we already have a lock, keeps the one we have.