Retrieving signal strengh values from oncreate method

Question

how to retrieve the value of strengthAmplitude at oncreate method inside Activity.

 private class SignalStrengthListener extends PhoneStateListener
         {

     @Override

    public void onSignalStrengthsChanged(android.telephony.SignalStrengthsignalStrength) 
         {                        

             // get the signal strength (a value between 0 and 31)
             int strengthAmplitude = signalStrength.getGsmSignalStrength();


            super.onSignalStrengthsChanged(signalStrength);
          }
    }