activity indicator before webView - iphone

Question

Good afternoon I have a difficulty using the "Activity indicator", I want it to appear in my view while I do the download of an XML into an NSData and when the download finished it becomes invisible.
tried, but the indicator only appears after the download is finished.
The code I used is simple, start the "Activity indicator" call the server URL, transfer to NSData and then stop the "Activity indicator" and call another View that presents the information in a WebView, and that is when the "Activity indicator" starts to load, I want the display to appear before loading the WebView appears.

Answer 1

You need to download on a different thread (not the main thread). Best way is to use GCD. Here is the sample code:
//Start Activity indicator on the main thread,
[activityIndicator performSelectorOnMainThread:#selector(startAnimating) withObject:nil waitUntilDone:YES];
dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Start Download code
dispatch_async( dispatch_get_main_queue(), ^{
[activityIndicator stopAnimating];
});
});

Answer 2

This is an example for UIActivityIndicatorView. It starts the spinner just before starting to download and stops the spinner when the block's completion handler is called. Remember to update the UI only from the main queue - in this case stopping the spinner.
-(void)test
{
CGRect screenRect = [[UIScreen mainScreen] bounds];
CGFloat screenWidth = screenRect.size.width;
CGFloat screenHeight = screenRect.size.height;
UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
[activityIndicator setCenter:CGPointMake(screenWidth/2.0, screenHeight/2.0)];
[self.view addSubview:activityIndicator];
[activityIndicator startAnimating];
NSMutableString *myURL = [[NSMutableString alloc] initWithString:#"http://www.domain.com/"];
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:[myURL stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding]]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection
sendAsynchronousRequest:urlRequest
queue:queue
completionHandler: ^( NSURLResponse *response,
NSData *data,
NSError *error)
{
if (error == nil)
{
// do whatever with data
dispatch_async(dispatch_get_main_queue(), ^{
[activityIndicator stopAnimating]; // stop spinner from the main queue
[activityIndicator removeFromSuperview];
});
} else // got an error
{
dispatch_async(dispatch_get_main_queue(), ^{
[activityIndicator stopAnimating]; // stop spinner from the main queue
[activityIndicator removeFromSuperview];
});
}
}];
}