don't display image in UIScrollView - ios

Question

I created 2 class (RecipeViewController & DetailViewController)
RecipeView is TableViewController that show me 4 cell (name of book) and DetailView is UIViewController that has UIScroll that show me many images of any book.
my problem is when I click on any cell and go to next page UIScroller dont show images to me.
this is my code:
RecipeViewController.m
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
int x = (indexPath.row)+1;
NSLog(#"x : %d",x);
DetailViewController *obj = [[DetailViewController alloc]init];
obj.yourValue = [NSString stringWithFormat:#"%d",(indexPath.row)+1];
[self presentModalViewController:obj animated:YES];
NSLog(#"yourValue1 : %#",obj.yourValue);
}
DetailViewController.m
#import "DetailViewController.h"
#import "RecipeViewController.h"
#implementation DetailViewController
#synthesize scroller,yourValue;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
//m1 variable tell me in tableview which choice book
int m1 = [self.yourValue integerValue];
NSLog(#"m1 : %d",m1);
//this code give me number of images (pages of book)
NSString *numberbook = [[NSString alloc]initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"http://192.168.1.102/mamal/book.php?info=0&b=%d",m1]]];
NSInteger numbook = [numberbook integerValue];
NSLog(#"%d",numbook);
for (int i = 1; i <= numbook; i++)
{
//this code for recive images from specific book
NSData *dat = [[NSData alloc]initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"http://192.168.1.102/mamal/book.php?p=%d&b=%d",i,m1]]];
NSLog(#"%#",dat);
UIImageView *imagen = [[UIImageView alloc] initWithImage:[UIImage imageWithData:dat]];
imagen.frame = CGRectMake((i-1)*320, 0, 320, 460);
[scroller addSubview:imagen];
}
scroller.delegate = self;
scroller.contentSize = CGSizeMake(320*numbook, 460);
scroller.pagingEnabled = YES;
}
#end
sorry for my weak english!!!

Answer 1

If you really want to use [NSData dataWithContentsOfURL:]; Add this inside your loop, chnage url and the imageView frame.
for (int i = 1; i <= numbook; i++)
{
UIImageView *yourImage=[[UIImageView alloc]init];
yourImage.frame = CGRectMake((i-1)*320, 0, 320, 460);
[scroller addSubview:imagen];
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
NSURL* url = [NSURL URLWithString:[NSString stringWithFormat:#"http://192.168.1.102/mamal/book.php?p=%d&b=%d",i,m1]];
NSData *imgData = [NSData dataWithContentsOfURL:url];
dispatch_sync(dispatch_get_main_queue(), ^{
UIImage *downloadedImage = [UIImage imageWithData:imgData];
yourImage.image = downloadedImage;
if(yourImage.image==nil)
{
[yourImage setImage:#"placeholder.png"];
}
});
});
}

Answer 2

Hey you are doing everything in the main thread and there can be a delay or some other problems generally it is not advised to do so , can you make use of NickLockWoods implementation for loading images asynchronously
https://github.com/nicklockwood/AsyncImageView
It is a very good category of UIImageView, you just have to import AsyncImageView and can use the function
[imageView setImageURL:#"ur url"];
It loads up all images asynchronously and it has so many customizations.
In your case:
for (int i = 1; i <= numbook; i++)
{
UIImageView *imagen = [[UIImageView alloc] initWithFrame: CGRectMake((i-1)*320, 0, 320, 460)];
[imagen setImageURL: [NSString stringWithFormat:#"192.168.1.102/mamal/book.php?p=%d&b=%d",i,m1]]];
[scroller addSubview:imagen];
}
You are doing everything in the main thread, that is why it is not loading images. In the same code that you are doing try giving background color of imageView and check.