问题
I am trying to implement a simple spinner while my app seeks data from the Internet. My data grab is working fine, but it sometimes takes a while, so I'd like to use a UIActivityIndicatorView to let the user know that the app hasn't crashed. But it's currently not working. I've gleaned as much as I can from these forums, and others, but for some reason it's not working. Again, I feel like this solution is probably very simple. Here's what I'm doing:
I declare the spinner as a property in the .h file:
@property (strong, nonatomic) IBOutlet UIActivityIndicatorView *activityIndicator;
I have also dragged a spinner object onto the viewcontroller using storyboard, and created a connection to the property using CTRL-drag.
The button that triggers the URL request (and consequent loading & parsing of data) actually triggers a segue, so I figure using the
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
function is as good a place as any to get things started. I don't have a specific function attached to the button apart from the prepareforsegue function. (Maybe this is an issue? does it need to have an IBAction associated?...)
Anyway, that function triggers this:
[self GoAheadAndGetData];
which, in turn, begins like so:
- (void)GoAheadAndGetData {
[NSThread detachNewThreadSelector:@selector(threadStartAnimating:) toTarget:self withObject:nil];
....... etc
So that function looks like this:
- (void) threadStartAnimating:(id)data
{
[activityIndicator startAnimating];
}
And finally, at the end of the GoAheadAndGetData function, I have placed the stop animating call, like so:
[activityIndicator stopAnimating];
Is that clear? Please let me know if anyone needs more info - I have tried to strip it down to basics, so I don't have to post a ton of code here...
Thank you in advance - I'd really appreciate any help I could get. I don't quite know why it's not working at this point.
来源：https://stackoverflow.com/questions/10145045/uiactivityindicatorview-not-appearing-ios-5