Dear Charlie,
Thank you so much for your reply.
I tested in browser and its working fine. Also I checked the fiori client code where its using the window.open(urlToAttachment) method to open the attachments.
The problem happens only in Android fiori client and I can open when the value of SAPKapselHandleHttpRequests is true. In this case, After login to the application my all https requests are failed and getting time out exception but http is working fine. I have to access some other https requests in my application those are pointing to a different domain.
For accessing https I changed the value of SAPKapselHandleHttpRequests in to false, then I can't open the attachments except this all are fine.
Regards,
Shafi