Why progressEvent.total returning -1 in phonegap

Why progressEvent.total returning -1 in phonegap

Im trying to download multiple files. File is downloading fine in my
device. But progressEvent giving some weird results. for all case
progressEvent.total returning -1. although progressEvent.loaded value
always changing . How to fix it.
function downloadFile(remoteUrl, localPath) {
var fileTransfer = new FileTransfer();
fileTransfer.onprogress = function(progressEvent) {
if (progressEvent.lengthComputable) {
var perc = Math.floor(progressEvent.loaded /
progressEvent.total * 100);
//statusDom.innerHTML = perc + "% loaded...";
statusDom.innerHTML = progressEvent.loaded + " - " +
progressEvent.total;
} else {
if(statusDom.innerHTML == "") {
statusDom.innerHTML = "Loading";
} else {
statusDom.innerHTML += ".";
}
}
};
fileTransfer.download(encodeURI(remoteUrl), localPath, function(e) {},
fail);
}