iOS / Phonegap : using FileTransfer response - ios

Question

first, sorry if my english is bad.
Then, here is my issue:
I try to make an app for iOS with PhoneGap 2.8.1 . Evrything is going well on Android, now I just want to move my code on Xcode to compile on iPad or iPhone.
The probleme I have is with FileTransfer, when I upload an image. The transfer itself has no problem, as it finishes with a response code 200, so it's a success.
Then, my serve is supposed to return back an XML file, handled by the javascript code. The server works fine, because I have absolutly no problem with Android devices.
So, I made a lot of tests, and it appears that the app has a problem with the success callback or the FileTransfer.upload(). When I just put a simple console.log('success') in this callback function, it's fine. But when I try to use the FileUploadResult object, nothing happens.
And the weirdest thing is, that when I press the main button of the iPad or iPhone, in order to close my app, I see all my logs displayed in the debug window, such as console.log("Code = " + r.responseCode);, like in the PhoneGap example. And here, I can finally see that I actually receive the server response, but it's like something blocks it until I close the app.
Here is that part of the code :
function onPhotoDataSuccess(imageURI) {
console.log("---> Image: "+imageURI);
// File Transfer
var options = new FileUploadOptions();
options.fileKey="file";
options.chunkedMode = false;
options.fileName=imageURI.substr(imageURI.lastIndexOf('/')+1);
options.mimeType="image/jpeg";
var ft = new FileTransfer();
ft.upload(imageURI, encodeURI(window.localStorage.getItem("wsURL")), win, fail, options);
// Transfer succeeded
function win(r) {
console.log("Code = " + r.responseCode);
console.log("Response = " + r.response);
console.log("Sent = " + r.bytesSent);
// Handle the XML response
}
else {
alert("No response. Please retry");
}
}
// Transfer failed
function fail(error) {
alert("An error has occurred: Code = " + error.code);
console.log("upload error source " + error.source);
console.log("upload error target " + error.target);
}
}
Thanks for your help