Question

I’ve been beating my head against a wall with this problem, and need some help.
I am trying to display a UIActivityIndicator while I load data in the background. I’m not sure if this is relevant or not, but I am loading a tableview. The indicator appears, but doesn’t spin…unless I touch the screen, or something else happens while loading-like if I receive a text message. Here is the code:

UIActivityIndicatorView  *av = [[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite] autorelease];
av.frame=CGRectMake(145, 160, 25, 25);
av.tag  = 1;
[self.mTableView addSubview:av];
[av startAnimating];
[self performSelectorInBackground:@selector(load) withObject:nil];

I’ve also tried this:

UIActivityIndicatorView  *av = [[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite] autorelease];
av.frame=CGRectMake(145, 160, 25, 25);
av.tag  = 1;
[self.view addSubview:av];
[av startAnimating];
[self performSelectorInBackground:@selector(load) withObject:nil];

and have tried it with commenting out the last line-So not having the background thread run. I have tried both versions of the code in my viewDidLoad and viewDidAppear methods.

Any ideas?

Edit Here is my load method

- (void)load {

NSString *post = [NSString stringWithFormat:@"id[]=%@", [ids objectAtIndex:0]];

for(int i = 1; i < ids.count; i++){
    post = [NSString stringWithFormat:@"%@&id[]=%@", post, [ids objectAtIndex:i]];
}


NSURL *url=[NSURL URLWithString:@"http://myurl/instructions"];

NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];

NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];
[request setURL:url];
[request setHTTPMethod:@"POST"];
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setHTTPBody:postData];

/* when we user https, we need to allow any HTTPS cerificates, so add the one line code,to tell teh NSURLRequest to accept any https certificate, i'm not sure about the security aspects
 */

//[NSURLRequest setAllowsAnyHTTPSCertificate:YES forHost:[url host]];

NSError *error;
NSURLResponse *response;
NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

NSString *data=[[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];

[self parseData:data];

[spinner stopAnimating];

}

Answer 1

The UI needs time to load, and can’t start the animation immediately. By starting it with an NSTimer in the viewDidLoad method, the problem was solved.

timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(spin) userInfo:nil repeats:NO];
[[NSRunLoop mainRunLoop] addTimer:self.timer forMode:UITrackingRunLoopMode];

and the scan method:

spinner = [[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite] autorelease];
spinner.center = self.view.center;
spinner.hidesWhenStopped = YES;
[spinner startAnimating];
[self.view addSubview:spinner];
if ([spinner isAnimating]) NSLog(@"animating");
else NSLog(@"not animating");

[self performSelectorInBackground:@selector(load) withObject:nil];

Hopefully this helps.