Download Multiple images using Native functionality IOS - iphone

Question

How to download multiple images and save it to the disk.
The Send request i'm using is below.
for(NSDictionary *image in [data objectForKey:#"Catalogues"])
{
NSString *imurl =[image objectForKey:#"Image_Path"];
NSLog(#"%#",imurl);
NSString *urlstring =imurl;
NSLog(#"demo %#",urlstring);
NSURL *mailurl =[NSURL URLWithString:urlstring];
NSMutableURLRequest *request =[NSMutableURLRequest requestWithURL:mailurl];
NSOperationQueue *ques =[[NSOperationQueue alloc]init];
[NSURLConnection sendAsynchronousRequest:request queue:ques completionHandler:^(NSURLResponse *respo, NSData *data, NSError *err) {
UIImage *image = [UIImage imageWithData:data];
UIImageView *im = [[UIImageView alloc] initWithFrame:CGRectMake(50, 100, 150, 150)];
im.image = image;
[self.view addSubview:im];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *getImagePath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:#"%#",documentsDirectory]
any native methods available for multiple images?

Answer 1

you can implement an AsyncImage class like this
in AsyncImage.h file
#import <UIKit/UIKit.h>
#interface AsyncImage : UIView
{
NSURLConnection* connection;
NSMutableData* data;
UIImageView *image;
UIActivityIndicatorView *scrollingWheel;
NSString *imgName;
}
-(void)loadImageFromString:(NSString*)url;
-(void)loadImageFromURL:(NSURL*)url;
-(void)setLocalImage:(UIImage *)localImage;
-(id) initWithFrame:(CGRect)frame;
-(NSString *)applicationDocumentsDirectory;
-(void)cancelConnection;
#end
in AsyncImage.m file
#import "AsyncImage.h"
#implementation AsyncImage
-(id)initWithFrame:(CGRect)frame
{
if ((self = [super initWithFrame:frame]))
{
scrollingWheel = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
float x = self.bounds.size.width/2;
float y = self.bounds.size.height/2;
scrollingWheel.center = CGPointMake(x, y);
scrollingWheel.hidesWhenStopped = YES;
[self addSubview:scrollingWheel];
self.clipsToBounds = YES;
}
return self;
}
-(void)loadImageFromString:(NSString*)url
{
[scrollingWheel startAnimating];
if (connection!=nil) {
[connection release];
connection = nil;
}
if (data!=nil) {
[data release];
data = nil;
}
if (image != nil) {
[image removeFromSuperview];
image = nil;
}
imgName = [[[url componentsSeparatedByString:#"/"] lastObject]retain];
// NSLog(#"imgName=%#",imgName);
NSString *imagePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent:imgName];
// NSLog(#"imagePath=%#",imagePath);
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:imagePath] == NO)
{
NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:60.0];
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
} else {
UIImage *img = [[UIImage alloc]initWithContentsOfFile:imagePath];
image = [[[UIImageView alloc] initWithImage:img] autorelease];
image.contentMode = UIViewContentModeScaleToFill;
image.frame = self.bounds;
[self addSubview:image];
[scrollingWheel stopAnimating];
}
}
-(void)setLocalImage:(UIImage *)localImage
{
if (image != nil) {
[image removeFromSuperview];
image = nil;
}
image = [[[UIImageView alloc] initWithImage:localImage] autorelease];
image.contentMode = UIViewContentModeScaleToFill;
image.frame = self.bounds;
[self addSubview:image];
}
//for URL
-(void)loadImageFromURL:(NSURL*)url
{
[scrollingWheel startAnimating];
if (connection!=nil) {
[connection release];
connection = nil;
}
if (data!=nil) {
[data release];
data = nil;
}
if (image != nil) {
[image removeFromSuperview];
image = nil;
}
NSString *strurl=[NSString stringWithFormat:#"%#",url];
imgName = [[[strurl componentsSeparatedByString:#"/"] lastObject]retain];
NSString *imagePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent:imgName];
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:imagePath] == NO)
{
NSURLRequest* request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:60.0];
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
} else {
UIImage *img = [[UIImage alloc]initWithContentsOfFile:imagePath];
image = [[[UIImageView alloc] initWithImage:img] autorelease];
image.contentMode = UIViewContentModeScaleToFill;
image.frame = self.bounds;
[self addSubview:image];
[scrollingWheel stopAnimating];
}
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
[data release];
data=nil;
[scrollingWheel stopAnimating];
}
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
data = [[NSMutableData data] retain];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)dataObj
{
[data appendData:dataObj];
}
-(void) connectionDidFinishLoading:(NSURLConnection *)theConnection
{
[connection release];
connection=nil;
NSString *imagePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent:imgName];
[data writeToFile:imagePath atomically:YES];
image = [[[UIImageView alloc] initWithImage:[UIImage imageWithData:data]] autorelease];
image.contentMode = UIViewContentModeScaleToFill;
image.frame = self.bounds;
[self addSubview:image];
[data release];
data=nil;
[scrollingWheel stopAnimating];
}
-(void)dealloc
{
[scrollingWheel release];
[super dealloc];
}
-(NSString *)applicationDocumentsDirectory
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
return basePath;
}
-(void)cancelConnection
{
if (connection !=nil) {
[connection cancel];
connection=nil;
}
if(data!=nil){
[data release];
data=nil;
}
[scrollingWheel stopAnimating];
}
#end
and at your viewController.m you can import this class and call it like this
AsyncImage *imgBOD = [[AsyncImage alloc] initWithFrame:CGRectMake(10, 46, 70, 70)];
[imgBOD loadImageFromString:[dictData objectForKey:#"image_path"]];
[self.view addSubview:imgBOD];

Answer 2

There is no "native method" for this particular problem.
If you just want to save a list of images to disk, you can improve your approach by not creating UIImages in the first place, just treat the data as binary data and save to disk directly.
In order to maintain low memory foot-print, implement NSURLConnection's delegate methods, and write (append) the image data piece-wise to the destination file as the chunk data arrives in connection:didReceiveData:.
The latter will be best solved by creating a dedicated class which encapsulates NSURLConnection and other related states and is subclassed from NSOperation and employs the asynchronous style implementing NSURLConnection delegates.
You might consider a third party library, too. A warning though: almost all well-known third party network libraries will not let you easily write data in pieces to a file. Per default, they accumulate all received data into one NSMutableData object. That may increase your memory-foot print, since images may be large, and since you can start multiple connections at once.
Also, don't start more than two connections at once.