download multiple images in iOS App - ios

Question

I want to download multiple images from URL to my device in iOS App.
//
// ImageDownload.m
//
#import "ImageDownload.h"
#implementation ImageDownload {
int *position;
NSArray *downloableImages;
}
- (void)start:(NSArray *)images delegate:(id)delegate
{
position = 0;
downloableImages = images;
NSUInteger *count = ((NSUInteger *)[downloableImages count]);
NSLog(#"%d", count);
[self startDownload];
}
- (void)startDownload
{
NSUInteger *imageDataCount;
NSArray *image;
NSString *filename;
NSString *fileurl;
NSURLRequest *imageUrlRequest;
image = [downloableImages objectAtIndex:position];
NSLog(#"%d", position);
NSArray *imageData = [image valueForKey:#"image"];
imageDataCount = ((NSUInteger *)[imageData count]);
if (imageDataCount > 0) {
filename = [imageData objectAtIndex:0];
fileurl = [imageData objectAtIndex:1];
NSLog(#"%#", fileurl);
imageUrlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:fileurl]];
NSURLConnection *imageUrlConnection = [[NSURLConnection alloc] initWithRequest:imageUrlRequest delegate:self startImmediately:TRUE];
} else {
NSUInteger *count = ((NSUInteger *)[downloableImages count]);
if (((NSUInteger *)position) < ((NSUInteger *)count - 1)) {
position = position + 1;
[self startDownload];
}
}
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(#"finish image...");
NSUInteger *count = ((NSUInteger *)[downloableImages count]);
if (((NSUInteger *)position) < ((NSUInteger *)count - 1)) {
position = position + 1;
[self startDownload];
}
}
#end
For now... I only check the position of the download and current URL,
Exists 27 files to download... but the download not go one by one... check this output:
Position: 0
http.....fichero00.jpg
Finish download
Position: 4
http.....fichero04.jpg
Finish download
Position: 8
http.....fichero08.jpg
Finish download

Answer 1

Create an ivar NSOperationQueue *operationQueue; in your .h file and init it in your .m file:
operationQueue = [[NSOperationQueue alloc] init];
operationQueue.maxConcurrentOperationCount = 1;
For downloading images, create a method that takes an image URL and call it for each image:
-(void)downloadImageAtURL:(NSURL *)imageURL {
[NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:imageURL] queue:operationQueue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
// Do something with your images here...
};
}

Answer 2

You can try this code.. Its 100 % Working for me
You can get more reference here
-(IBAction)startdownload
{
for (int i=0; i<[downloadarray count]; i++) //download array have url links
{
NSURL *URL = [NSURL URLWithString:[downloadarray objectAtIndex:i]];
NSMutableURLRequest *urlRequest = [[NSMutableURLRequest alloc]initWithURL:URL];
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if([data length] > 0 && [[NSString stringWithFormat:#"%#",error] isEqualToString:#"(null)"])
{
//make your image here from data.
UIImage *imag = [[UIImage alloc] initWithData:[NSData dataWithData:data]];
NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docDir = [array objectAtIndex:0];
NSString *imgstr=[NSString stringWithFormat:#"%d",i];
NSString *pngfilepath = [NSString stringWithFormat:#"%#sample%#.png",docDir,imgstr];
NSData *data1 = [NSData dataWithData:UIImagePNGRepresentation(imag)];
[data1 writeToFile:pngfilepath atomically:YES];
}
else if ([data length] == 0 && [[NSString stringWithFormat:#"%#",error] isEqualToString:#"(null)"])
{
NSLog(#"No Data!");
}
else if (![[NSString stringWithFormat:#"%#",error] isEqualToString:#"(null)"]){
NSLog(#"Error = %#", error);
}
}];
}
-(IBAction)viewfile
{
NSMutableArray *arr=[[NSMutableArray alloc]init];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *pngfilepath = [NSString stringWithFormat:#"%#",documentsDirectory];
NSArray *filePathsArray = [[NSFileManager defaultManager] subpathsOfDirectoryAtPath:pngfilepath error:&error];
for (int i=0; i<[filePathsArray count]; i++){
NSString *pngfilepath = [NSString stringWithFormat:#"%#%#",documentsDirectory, [filePathsArray objectAtIndex:i]];
[arr addObject:[UIImage imageWithContentsOfFile:pngfilepath]];
}
myimageview = [[UIImageView alloc] initWithImage:[arr objectAtIndex:0]]; //Here myimageview is UIImageView
}
Hope This Helps!!!

Answer 3

Work around NSOperationQueue it allow you to control how much operation are run concurrently.
Create:
NSOperationQueue *queue = [NSOperationQueue new];
queue.maxConcurrentOperationCount = 1;
Then add operations :
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
... here is you code with converting image to data and addition it to NSURLConnection
}];
[operation setCompletionBlock:^{
....something that you want to do, after operation completes
}];
[queue addOperation:operation];
More about NSOperation:
https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/NSOperation_class/Reference/Reference.html#//apple_ref/occ/cl/NSOperation

Answer 4

Here is my new code...
I have a delay when I try to update a UIProgressView
//
// ImageDownload.m
//
#import "ImageDownload.h"
#implementation ImageDownload {
NSMutableArray *downloableImages;
int position;
Sync *mySync;
}
- (void)start:(NSArray *)images sync:(Sync *)sync
{
NSArray *imageData;
int imageDataCount;
mySync = sync;
downloableImages = [[NSMutableArray alloc] init];
for (NSArray *image in images) {
imageData = [image valueForKey:#"image"];
imageDataCount = [imageData count];
if (imageDataCount > 0) {
[downloableImages addObject:imageData];
}
}
[self downloadAllFiles];
}
- (void)downloadAllFiles
{
NSString *filename;
NSString *fileUrl;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *cacheDirectory = [paths objectAtIndex:0];
position = 0;
int count = [downloableImages count];
NSLog(#"%#", downloableImages);
NSLog(#"total files %d", count);
for (NSArray *image in downloableImages) {
filename = [image objectAtIndex:0];
fileUrl = [image objectAtIndex:1];
NSURL *url = [NSURL URLWithString:fileUrl];
NSMutableURLRequest *urlRequest = [[NSMutableURLRequest alloc] initWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
position++;
float progress = (float)position / (float)count;
//update UIProgressView
[mySync setProgressImageDownload:progress];
if ([data length] > 0 && [[NSString stringWithFormat:#"%#", error] isEqualToString:#"(null)"]) {
UIImage *downloadedImage = [[UIImage alloc] initWithData:[NSData dataWithData:data]];
NSString *imageDestinationPath = [NSString stringWithFormat:#"%#%#", cacheDirectory, filename];
NSData *imageData = [NSData dataWithData:UIImageJPEGRepresentation(downloadedImage, 100.0)];
[imageData writeToFile:imageDestinationPath atomically:YES];
}
if (position == count) {
NSLog(#"all complete...");
[mySync downloadImagesComplete];
}
}];
}
}
#end