UIScrollView dynamic contents not appearing - ios

Question

I'm having a trouble dynamically adding UIButtons with background image as subviews to a UIScrollView. Its kind of a image gallery using UIButtons on a scrollView. I have used this method for couple of my apps, it works fine for me with the static contents.
But this time, Im loading images from a web service and saved to documents directory, then call the method to create the gallery. Logic is same with my other apps. But I cannot figure out what is the issue here.
I'll put here both the codes one is for retrieving data and other is the creating gallery.
Data retrieving from server
-(void)loadDataFromServer{
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
arrCats = [[NSMutableArray alloc]init];
arrPromos = [[NSMutableArray alloc]init];
//[spinMenu startAnimating];
// load promo images from the server
for(int i=0;i<[arrPromos count];i++)
{
NSString *urlString = [Constants getImages:[[arrPromos objectAtIndex:i] objectForKey:#"image"]];
NSLog(#"Get Images API Call : %#", urlString);
NSURL *imageurl = [NSURL URLWithString:urlString];
//get a dispatch queue
dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
//this will start the image loading in bg
dispatch_async(concurrentQueue, ^{
NSData *imageData = [[NSData alloc] initWithContentsOfURL:imageurl];
//this will set the image when loading is finished
dispatch_async(dispatch_get_main_queue(), ^{
if(imageData != nil){
// save the images temporally
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsPath = [paths objectAtIndex:0]; //Get the docs directory
NSString *filePath = [documentsPath stringByAppendingPathComponent:[[arrPromos objectAtIndex:i] objectForKey:#"image"]]; //Add the file name
[imageData writeToFile:filePath atomically:YES];
}
});
});
}
// Load promotions from server
dispatch_async(queue, ^{
NSLog(#"Promotions Loading Started");
NSString *urlString = [Constants getAllPromotions:#"GetPromo.php"];
NSLog(#"Get Promotions API Call : %#", urlString);
NSURL *url = [NSURL URLWithString:urlString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
// Specify that it will be a GET request
request.HTTPMethod = #"GET";
[request setHTTPShouldHandleCookies:NO];
NSURLResponse *responseURL;
NSError *error;
NSData *dataPromotions = [NSURLConnection sendSynchronousRequest:request returningResponse:&responseURL error:&error];
if (responseURL == nil)
{
// Check for problems
if (error != nil)
{
NSLog(#"Get Promtions Connection failed! Error - %#", [error localizedDescription]);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Connection Error!" message:#"Promotions data failed to load!" delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
}
}
else
{
NSString *responseString = nil;
responseString = [[NSString alloc] initWithData:dataPromotions encoding:NSUTF8StringEncoding];
if ([responseString rangeOfString:#"error"].location == NSNotFound)
{
NSDictionary *response = [[NSDictionary alloc] init];
response = (NSDictionary *)[responseString JSONValue];
NSLog(#"Response : Promotions %#", response);
if(response != Nil){
if([response count]>0){
arrPromos = [NSMutableArray arrayWithArray:[response objectForKey:#"Promos"]];
NSLog(#"ArrPromos # loading %#", arrPromos);
// create promos galley
[self createPromosGallery];
}
}
}
}
});
Note: [self createPromosGallery]; is calling after download all the images and data.
Create Gallery
-(void) createPromosGallery{
// sort arrPromos based on priority
for(int i=0; i<[arrPromos count];i++){
[arrPromos sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSDictionary *dict1 = obj1;
NSDictionary *dict2 = obj2;
NSString *string1;
NSString *string2;
if(![[dict1 objectForKey:#"priority"] isKindOfClass: [NSNull class]])
string1 = [dict1 objectForKey:#"priority"];
if(![[dict2 objectForKey:#"priority"] isKindOfClass: [NSNull class]])
string2 = [dict2 objectForKey:#"priority"];
return [string1 compare:string2 options:NSNumericSearch];
}];
}
NSLog(#"ArrPromos %#", arrPromos);
// scrollView size
CGFloat screenHieght = [UIScreen mainScreen].bounds.size.height;
if(screenHieght>500){
scrollView.frame = CGRectMake(0, 0, 320, 568);
}
else{
scrollView.frame = CGRectMake(0, 0, 320, 480);
}
// define scrollview height
int scrollHieght;
scrollHieght = ([arrPromos count]-1)/2;
NSLog(#"Scroll height %d",scrollHieght);
scrollView.contentSize = CGSizeMake(scrollView.frame.size.width , scrollHieght * 160 +200);
scrollView.pagingEnabled = NO;
scrollView.showsHorizontalScrollIndicator = NO;
scrollView.showsVerticalScrollIndicator = NO;
scrollView.scrollsToTop = NO;
scrollView.decelerationRate = UIScrollViewDecelerationRateFast;
scrollView.delegate = self;
for(int i=0;i<[arrPromos count];i++)
{
float x;
float y;
if(i%2==0)
{
x=30.0;
y=(i/2)*160+25;
}
if(i%2==1) {
x=170.0;
y=(i/2)*160+25;
}
// retreive saved images
NSString *strImgName;
UIImage *buttonUpImage;
// create buttons
button = [UIButton buttonWithType:UIButtonTypeCustom];
strImgName = [[arrPromos objectAtIndex:i] objectForKey:#"image"];
NSLog(#"Button image name %#", strImgName);
NSArray *sysPaths = NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES );
NSString *docDirectory = [sysPaths objectAtIndex:0];
NSString *filePath = [NSString stringWithFormat:#"%#/%#",docDirectory,strImgName];
buttonUpImage = [UIImage imageWithContentsOfFile:filePath];
[button setBackgroundImage:buttonUpImage forState:UIControlStateNormal];
button.frame = CGRectMake(x, y, 120,140);
[button setTag:i];
[button addTarget:self action:#selector(promoBtnPressed:)forControlEvents:UIControlEventTouchUpInside];
[self.scrollView addSubview:button];
}
}
Note: I tested on both iOS 7 and 6. In iOS 7, it takes very long time to appear images on scrollView(Currently have only 2 images). Or else, If I TAP on scroolView then the images appear.
In ios 6, nothing appear

Answer 1

//Make a method that has url (fileName) Param
NSArray *documentsDirectory =
NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES);
NSString *textPath = [documentsDirectory stringByAppendingPathComponent:url];
NSFileManager *fileManager =[NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:textPath])
{
return YES;
}
else
{
return NO;
}
UIImageView *imgView = [[UIImageView alloc] initWithImage:[UIImage
imageNamed:#""]];//Placeholder image
if ([url isKindOfClass:[NSString class]])
{
imgView.image = [UIImage imageNamed:[url absoluteString]];
imgView.contentMode = UIViewContentModeScaleAspectFit;
}
else if ([fileManager fileExistsAtPath:url])
{
NSString *textPath = [documentsDirectory stringByAppendingPathComponent:url];
NSError *error = nil;
NSData *fileData = [NSData dataWithContentsOfFile:textPath options:NSDataReadingMappedIfSafe error:&error];
if (error != nil)
{
DLog(#"There was an error: %#", [error description]);
imgView.image=nil;
}
else
{
imgView.image= [UIImage imageWithData:fileData]
}
}
else
{ UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc]
initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
CGPoint center = imgView.center;
// center.x = imgView.bounds.size.width / 2;
spinner.center = center;
[spinner startAnimating];
[imgView addSubview:spinner];
dispatch_queue_t downloadQueue = dispatch_queue_create("iamge downloader", NULL);
dispatch_async(downloadQueue, ^{
NSData *imgData = [NSData dataWithContentsOfURL:url];
dispatch_async(dispatch_get_main_queue(), ^{
[spinner removeFromSuperview];
UIImage *image = [UIImage imageWithData:imgData];
NSError *error = nil;
[imgData writeToFile:url options:NSDataWritingFileProtectionNone error:&error];
if (error != nil)
}
else
{
}
imgView.image = image;
});
});
}
Thats UIImageView loading an image if it doesnot exist in document then it Save it , An Activity indicator is added to show image is loading to save,

Answer 2

Yes it is because you are downloading and then saving the images which takes time. I suggest you to use any library for downloading images and saving them.
Ex : SDWebImage