showing UIActivityIndicator on fetch of XML - ios

Question

what im trying to do is parse an XML data and show it in my UITableView but the thing is it shows like after 2-3 seconds, im trying to include a UIActivityIndicator when the data loads and also im trying to include a gcd, but the thing is im new at this stuff so im really confuse on what to do or where do i posible put the gcd code.
that is my .m file.
#implementation ViewController
#synthesize listTableView;
dispatch_queue_t myQueue;
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [[xmlParser listPopulated]count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString *CellIdentifier = #"CustomCell";
dataFileHolder *currentData = [[xmlParser listPopulated] objectAtIndex:indexPath.row];
CustomCellXMLClass *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(cell == nil) {
cell = [[CustomCellXMLClass alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"cell"];
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"CustomCellXMLSample" owner:self options:nil];
cell = [nib objectAtIndex:0];
}
NSString *nameLabel = [currentData nameOfCat];
NSString *dataToCacheLabel = [myCache objectForKey:nameLabel];
if(nameLabel != nil){
dataToCacheLabel = [NSString stringWithString:nameLabel];
if (dataToCacheLabel != nil) {
[myCache setObject:dataToCacheLabel forKey:nameLabel];
[cell.nameLabel setText:dataToCacheLabel];
}
}
NSString *detailLabel = [currentData descriptionOfCat];
NSString *stringToCache = [myCache objectForKey:detailLabel];
if (detailLabel != nil) {
stringToCache = [NSString stringWithString:detailLabel];
if (stringToCache != nil) {
[myCache setObject:stringToCache forKey:detailLabel];
[cell.detailLabel setText:stringToCache];
}
}
NSString *imageURL = [currentData imageLink];
NSData *dataToCache;
if (imageURL != nil) {
dataToCache = [NSData dataWithContentsOfURL:[NSURL URLWithString:imageURL]];
if (dataToCache != nil) {
[myCache setObject:dataToCache forKey:imageURL];
[cell.imageShow setImage:[UIImage imageWithData:dataToCache]];
}
else {
NSURL *imageURL = [NSURL URLWithString:#"http://i178.photobucket.com/albums/w255/ace003_album/190579604m.jpg"];
dataToCache = [NSData dataWithContentsOfURL:imageURL];
[myCache setObject:dataToCache forKey:imageURL];
[cell.imageShow setImage:[UIImage imageWithData:dataToCache]];
}
}
return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 78;
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{
NSString *title = #"Sample View";
return title;
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self.activityIndicator startAnimating];
self.activityIndicator.hidesWhenStopped = YES;
dispatch_queue_t myQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(myQueue, ^ {
xmlParser = [[XMLParser alloc]loadXMLByURL:#"http://www.irabwah.com/mobile/core.php?cat=0"];
[self.activityIndicator performSelectorOnMainThread:#selector(stopAnimating) withObject:nil waitUntilDone:YES];
});
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end

Answer 1

Depending on how XMLParser works your current CGD block is ok for that. You wouldn't usually use performSelectorOnMainThread to return the UI interaction to the main thread but that's just a common convention thing.
Most of your problem could be coming from dataWithContentsOfURL: which you're calling on the main thread in cellForRowAtIndexPath:. You might want to take a look at SDWebImage to help with that, but you could do it yourself with GCD too.

Answer 2

cellForRowAtIndexPath will not be called just because your XML finished loading. In your code block, I suggest before calling stopAnimating that you call reloadData on your UITableView; this will trigger a series of calls, first to numberOfRowsInSection and then to cellForRowAtIndexPath repeatedly. Try putting breakpoints in these functions so you can see the flow of execution.