Why loading data Indicator is not working properly? - ios

Question

In my code I am using an UIActivityIndicatorView on an UIAlertView. It is working fine but my problem is it is not showing up on correct time. I mean to say when the device get data from web service after that this loading indicator is appearing in the end and its not rite thing I think because I want it to be appear when the web service is sending or receiving data.
I need help as I am new to iOS app development. If there is any other easy way to do this thing then suggest me.
I hope my question is clear, my problem is according to this code the loading indicator is appearing after i get reply from web service but i want to run this indicator as the user will press update button and web service should be called after that. Tell me where i am wrong.
Here is the code I am using
-(IBAction)update:(id)sender
{
av=[[UIAlertView alloc] initWithTitle:#"Updating Image..." message:#"" delegate:self cancelButtonTitle:nil otherButtonTitles:nil];
ActInd=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
[ActInd startAnimating];
[ActInd setFrame:CGRectMake(125, 60, 37, 37)];
[av addSubview:ActInd];
[av show];
{
NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults];
int gid=[defaults integerForKey:#"gid"];
NSString *gameid=[NSString stringWithFormat:#"%i", gid];
NSLog(#"%#",gameid);
img=mainImage.image;
NSData *imgdata=UIImagePNGRepresentation(img);
NSString *imgstring=[imgdata base64EncodedString];
NSLog(#"%#",imgstring);
NSString *escapedString = (NSString *)CFURLCreateStringByAddingPercentEscapes(
NULL,
(CFStringRef)imgstring,
NULL,
CFSTR("!*'();:#&=+$,/?%#[]"),
kCFStringEncodingUTF8);
NSLog(#"escapedString: %#",escapedString);
#try
{
NSString *post =[[NSString alloc] initWithFormat:#"gid=%#&image=%#",gameid,escapedString];
NSLog(#"%#",post);
NSURL *url=[NSURL URLWithString:#"http://mywebspace/updategameimage.php"];
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength = [NSString stringWithFormat:#"%d", [postData length]];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:url];
[request setHTTPMethod:#"POST"];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:postData];
NSError *error = [[NSError alloc] init];
NSHTTPURLResponse *response = nil;
NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSLog(#"Response code: %d", [response statusCode]);
if ([response statusCode] >=200 && [response statusCode] <300) {
NSString *responseData = [[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];
NSLog(#"Response ==> %#", responseData);
SBJsonParser *jsonParser = [SBJsonParser new];
NSDictionary *jsonData = (NSDictionary *) [jsonParser objectWithString:responseData error:nil];
NSLog(#"%#",jsonData);
NSInteger type = [(NSNumber *)[jsonData objectForKey:#"type"] integerValue];
NSLog(#"%d",type);
if (type==1) {
[self alertStatus:#"You can Keep on Drawing" :#"Sketch Updated"];
}
}
}
#catch (NSException * e) {
NSLog(#"Exception: %#", e);
[self alertStatus:#"Unable to connect with game." :#"Connection Failed!"];
}
}
[av dismissWithClickedButtonIndex:0 animated:YES];
[av release]; av=nil;
}

Answer 1

UI updates are done on main thread. You have started activity indicator on main thread.It's fine.
Now, you are making synchronous network call on main thread. It should be asynchronous. Here until you will receive the response from network call, your main thread will remain busy and your UI will not be updated.
To update the UI, you can either make the network call asynchronous or you can start the activity indicator in a separate function and then delay the call of network activity by performselector:afterdelay method.

Answer 2

You can use GCD, Raywenderlich Tutorial
-(IBAction)update:(id)sender
{
/*
Setup indicator and show it
*/
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
/*
Do network call
*/
dispatch_async(dispatch_get_main_queue(), ^{
/*
Update UI
*/
});
});
}