Decode Listener

Register an  IReadListener in your Activity.OnResume() to receive read events on successful barcode reads:

protected override void OnResume()
{
	base.OnResume();

	if (decoder == null)
	{
		decoder = new BarcodeManager();
	}

	try
	{
		decoder.AddReadListener(this);
	}
	catch (DecodeException e)
	{
		Log.Error(LOGTAG, "Error while trying to bind a listener to BarcodeManager", e);
	}
}

Unregister the IReadListener in your Acvivity.onPause():

protected override void OnPause()
{
	base.OnPause();

	if (decoder != null)
	{
		try
		{
			decoder.RemoveReadListener(this);
		}
		catch (Exception e)
		{
			Log.Error(LOGTAG, "Error while trying to remove a listener from BarcodeManager", e);
		}
	}
}

The actual barcode scanning is started via any physical scan trigger on the device. Though to start scanning when a button on the application is pressed, you need to call  BarcodeManager.StartDecode() .