UIActivityIndicatorView not staring

Question

I am trying to set a 'UIActivityIndicatorView' as an accessoryView in one of my 'UITableViewCell', in a such way as, the ActivityIndicator start animating when the user touch this cell. I add the following code at 'didSelectRowAtIndexPath' method:

UITableViewCell * cell = [tableView cellForRowAtIndexPath:indexPath];

UIActivityIndicatorView * activity = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

NSThread * newThread1 = [[NSThread alloc]initWithTarget:self selector:@selector(carregarNoticias) object:nil];

switch (indexPath.row) {
    case 0:
        cell.accessoryView = activity;
        [activity startAnimating];
        sleep(0.01);
        [newThread1 start];

        while (![newThread1 isFinished]) {
            //waiting for thread
       }

        [activity stopAnimating];
[self.navigationController pushViewController:noticias animated:YES];
break; 

I was expecting 'UIActivityIndicatorView' animating while the newthread1 is running. However, the animating only start when the newThread1 finish (and therefore I don't want the animation anymore). I added 0.01 seconds as sleep time to give time to the animation start. Nevertheless, this also did't solve.

Does anyone know what my error is? I appreciate any help!

Answer 1

I dont really know what you are trying to do adding delay like that.. try this line below, might be the one your look for.. and another thing.. please dont block the main thread like sleep(0.01); that, users wont like it..

cell.accessoryView = activity;

[activity startAnimating];

dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){

    // the system will wait until this 
    dispatch_async(dispatch_get_main_queue(), ^(void){

        [newThread1 start];

    });
    // is finished, maybe you dont need the `[NSThread sleepForTimeInterval:3];` 
    // pick the one that suits your implementation.. 

    [NSThread sleepForTimeInterval:3];

    dispatch_async(dispatch_get_main_queue(), ^(void){

        [activity stopAnimating];

        [self.navigationController pushViewController:noticias animated:YES];

    });
});

[NSThread sleepForTimeInterval:3] sleep the thread like the one you have sleep(0.01);

But using it inside

dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){  });

makes it async. and wont block the main thread..

while the dispatch_async(dispatch_get_main_queue(), ^(void){ fires your code at the main thread..

Happy coding, cheers! :)