Android use getDataString to get custom URL-Scheme problem

Question

Custom URL Scheme works and getDataString gets correct url's perfectly BUT it gets null in one situation: when myapp is not in background, I scan a QR Code myapp://A to active myapp, after then, scan any other QR Code(myapp://B, C, ...) will get correct url's but scan the initial myapp://A always get null. Is that normal? How to get the url in QR Code EVERYTIME?