web runtime app coding:
function download() {
var url = "http://www.xxx.com/xxx.wgz";
var urlEncoded = encodeURI(url);

download xxx.wgz file by Browser. First, run app with above code,call bowser to download file, it do well.
Redo it later, popup browser, not download file. If clear cache in browser, redo it ,it do well.

How to solve this problem of downloading file?

Thank you very much!