how to use onActivityResult(..) if the activity is called from a menu

This is my problem:

class main extends menuActivity{
  //
  ..
  //
  public void onActivityResult(int requestCode, int resultCode, Intent data) {
     if (resultCode == 0) 
        camera_barcode = INTENT.getStringExtra("SCAN_RESULT");
     }
  }
}

the INTENT is created in the menuActivity class:

public class menuActivity extends Activity {

    public INTENT;
@Override
public boolean onCreateOptionsMenu(Menu menu) {

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

       //
       INTENT = new Intent("com.google.zxing.client.android.SCAN");
       INTENT.putExtra("SCAN_MODE", "QR_CODE_MODE");
       startActivityForResult(INTENT, 0);
       //
    }
} 

The problem is that the String camera_barcode is null, can't understand why.

Q: if instead of QR_CODE_MODE I want to scan 1d barcodes? R: cameraScan.putExtra("SCAN_MODE", "PRODUCT_MODE");

Thank you!!