Android : App Inventor : Webview for download and upload file

I try to make android application web base using webview app inventor, and in my application, there is a link for download report .xls document, but it's only showing like the picture below but no file has downloaded, can anyone help me..

screenshoot at my android : http://goo.gl/yZdmnq

screenshoot at my app inventor blocks : http://goo.gl/JE6QL2

Thanks before..