How to automatically request in the background？ - ios

Question

I need to upload an Image to the sever, and have to request in the background in case of the user press the home button.
- (void)uploadImage
{
AppDelegate * app = (AppDelegate *)[UIApplication sharedApplication].delegate;
[app.uploadAndDownManager uploadIDImageWithImage:_im.image];
}
-(void)uploadIDImageWithImage:(UIImage *)image
{
if (!_uploadImage) {
_uploadImage = image;
}
[self uploadImageInBackground];
}
- (void)uploadImageInBackground
{
_uploadImageTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[[UIApplication sharedApplication] endBackgroundTask:_uploadImageTask];
_uploadImageTask = UIBackgroundTaskInvalid;
}];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task, preferably in chunks.
// your code
// NSLog(#" %f",[UIApplication sharedApplication].backgroundTimeRemaining);
[self test];
[[UIApplication sharedApplication] endBackgroundTask:_uploadImageTask];
_uploadImageTask = UIBackgroundTaskInvalid;
});
}
-(void)test
{
NSString * userStr = [[NSUserDefaults standardUserDefaults] objectForKey:#"userName"];
NSString * portNumber = [[NSUserDefaults standardUserDefaults] objectForKey:#"portNumber"];
NSString * urlStr = URL_ADDRESS(portNumber, #"uploadAction_execute.action");
NSURL * url = [NSURL URLWithString:urlStr];
NSData * data = UIImageJPEGRepresentation(_uploadImage, 0.8);
//保存本地
[self saveToLocalDocument:data];
ASIFormDataRequest * re = [ASIFormDataRequest requestWithURL:url];
re.delegate = self;
[re setData:data withFileName:[NSString stringWithFormat:#"%#_id_.jpg",userStr] andContentType:#"image/jpg" forKey:#"file"];
[re setRequestMethod:#"POST"];
[re setDidFinishSelector:#selector(finish:)];
[re setDidFailSelector:#selector(failed:)];
// [re startAsynchronous];
[re startSynchronous];
}
In case the request is failed, I let it request automatically:
- (void)failed:(ASIFormDataRequest *)request
{
NSLog(#"error %#",request.error);
[self performSelector:#selector(uploadIDImageWithImage:) withObject:nil afterDelay:REQUEST_AGAIN_TIME];
// [SVProgressHUD showImage:nil status:#"验证提交成功，等待审核"];
}
When I press the home button, it may works but it can be out of time sometimes. When it fails, it won't request again! If the request asynchronous, it won't work until I enter the foreground again.
How can I fix it?

Answer 1

I put the code
[[UIApplication sharedApplication] endBackgroundTask:_uploadImageTask];
_uploadImageTask = UIBackgroundTaskInvalid;
in the success method finish:, it seems worked:
If there are other methods or any problem in this way, please let me know, thanks!