Using wrapper class in android studio

I've implemented a wrapper class according to this guide for the barcode functionality and when I try to use this wrapper class in my activity I get a nullpointerexception for the barcodeManager. When debugging I verify that the OnOpened method of the EMDKListener interface is not being called. Any hint? Here is the partial code for the wrapper class:

 

public class ZebraBarcode implements EMDKListener, DataListener, StatusListener{

   

    private Context mContext=null;

    private EMDKManager mEmdkManager=null;

    private BarcodeManager mBarcodeManager=null;

    private Scanner mScanner=null;

    private ScanDataCollection mScanDataCollection=null;

    private StatusData mStatusData=null;

   

    public ZebraBarcode(Context context){

        this.mContext=context;

    }

 

    public boolean getEMDKManager(){

        boolean bManager=true;

        EMDKResults results = EMDKManager.getEMDKManager(mContext, this);

        if(results.statusCode != EMDKResults.STATUS_CODE.SUCCESS){

            bManager=false;

        }

        return bManager;

    }   

   

    @Override

    public void onOpened(EMDKManager emdkManager) {

        this.mEmdkManager=emdkManager;

    }

 

In my activity I call this class:

 

if(Build.MANUFACTURER.contains("Zebra Technologies")

  || Build.MANUFACTURER.contains("Motorola Solutions")){

   mBarcodeSystem = new ZebraBarcode(mContext);
  if(!mBarcodeSystem.getEMDKManager()){

  Log.e(TAG,mContext.getString(R.string.error_message_barcode_manager_not_initiated));
   }