Question

I have 2 main small image buttons say aBtn & bBtn. When i click aBtn / bBtn i Generate 6 image url as default checking the condition that the images are not nil. In the 6 images if some images are empty then i avoid that empty image alone & set the frame accordingly. When i click from aBtn to bBtn, i have the time delay. It is due to checking the 6 url images generate without nil/empty image each time & by setting the frame position accordingly.

This is the code i used to display the images & check the condition from the 6 url images data is not nil if something say 3rd url image is nil it will be avoided. How to overcome the delay to display the images?

    NSMutableString *strUrl;
    int i;
    int j=7;
    int k=0;
    xorigin=350;
    int cou=1;

    for( i=1;i<j;i++){

        strUrl=[[NSMutableString alloc]init];
        UIImageView *imageView= [[UIImageView alloc]init];


        [strUrl appendFormat:@"http://commondatastorage.googleapis.com/images2.solestruck.com/%@%@%@%@%@%@%@)-01060%d.jpg",
         [[[[shoeDetailDict objectForKey:@"vendorName"] lowercaseString] lowercaseString] stringByReplacingOccurrencesOfString:@" " withString:@"-"],@"-shoes/",[[shoeDetailDict objectForKey:@"vendorName"] stringByReplacingOccurrencesOfString:@" " withString:@"-"],@"-shoes-",[[shoeDetailDict objectForKey:@"productName"] stringByReplacingOccurrencesOfString:@" " withString:@"-"],@"-(",[[prdcolorimgArray objectAtIndex:tagedColor] stringByReplacingOccurrencesOfString:@" " withString:@"-"],i];

        NSURL *imageUrl=[[NSURL alloc]initWithString:strUrl];

        NSError *error;
        NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:strUrl] options:NSDataReadingUncached error:&error];
        NSLog(@"imageurl colors : %@",strUrl);

        if(i==4){

            imageView.frame =CGRectMake(25, 0, (self.view.frame.size.width*80)/100,(self.view.frame.size.height*40)/100);
            [imageView setImageWithURL:imageUrl];
        }

        else{

            if(data != nil ){
                cou++;
                imageView.frame =CGRectMake(xorigin, 0, (self.view.frame.size.width*80)/100,(self.view.frame.size.height*40)/100);
                [imageView setImageWithURL:imageUrl];
                xorigin=xorigin+320;

            }
        }
        imageView.backgroundColor=[UIColor whiteColor];
        [productScroll addSubview:imageView];
        productScroll.contentSize = CGSizeMake((self.view.frame.size.width)*cou, (self.view.frame.size.height*40)/100);
        productScroll.contentOffset=CGPointMake(0, 0);

        k++;
    }

Answer 1

You are using dataWithContentsOfURL: that load information synchronously.

Try to load all images first and than put them on the scroll view.

Try to use this code:

- (void) prepareImages {
    dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{
        NSMutableArray * imagesArray = [NSMutableArray array];
        // Load all images here
        [self imagesLoaded:imagesArray]
    });
}
- (void) imagesLoaded:(NSArray*) images {
     dispatch_async(dispatch_get_main_queue(), ^{
        //Display images here
    });
}