UITableViewCell accessoryView not appearing until much later - iphone

Question

I've got a UITableView with several entries. Upon selecting one, I need it to do a potentially time-consuming network operation. To give the user some feedback, I tried to place a UIActivityIndicatorView in the UITableViewCell. However, the spinner doesn't appear until much later -- after I've done the expensive operation! What am I doing wrong?
- (NSIndexPath *) tableView:(UITableView *) tableView
willSelectRowAtIndexPath:(NSIndexPath *) indexPath {
UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc]
initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
[spinner autorelease];
[spinner startAnimating];
[[tableView cellForRowAtIndexPath:indexPath] setAccessoryView:activity];
if ([self lengthyNetworkRequest] == nil) {
// ...
return nil;
}
return indexPath;
}
As you can see, I have the spinner being set to the accessoryView before the lengthy network operation. But it only appears after the tableView:willSelectRowAtIndexPath: method finishes.

Answer 1

Once you tell the ActivityIndicator to start animating, you have to give your application's run loop a chance to start the animation before starting the long operation. This can be achieved by moving the expensive code into its own method and calling:
[self performSelector:#selector(longOperation) withObject:nil afterDelay:0];

Answer 2

EDIT: I think you should be using didSelect instead of willSelect.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
Try adding [CATransaction flush] right before
if ([self lengthyNetworkRequest] == nil) {

Answer 3

- (NSIndexPath *) tableView:(UITableView *) tableView
willSelectRowAtIndexPath:(NSIndexPath *) indexPath {
UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc]
initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
[spinner autorelease];
[spinner startAnimating];
[[tableView cellForRowAtIndexPath:indexPath] setAccessoryView:activity];
if ([self lengthyNetworkRequest] == nil) {
//doing the intensive work after a delay so the UI gets updated first
[self performSelector:#selector(methodThatTakesALongTime) withObject:nil afterDelay:0.25];
//you could also choose "performSelectorInBackground"
}
return indexPath;
}
- (void)methodthatTakesALongTime{
//do intensive work here, pass in indexpath if needed to update the spinner again
}