I have a wierd problem. The requirement is to download image from a url on swipe and display it in image view .It is working all fine but I am getting memory warnings after 30 images and after few more swipe app crashes.
Implementation is pretty straight forward,but already spent almost 2 days to figure out the issue.
On each swipe i am calling A method :-
-(void)callDownloadImageAPI{
NSAutoreleasePool *pool=[[NSAutoreleasePool alloc] init];
[self loadIndicator:#"Please Wait.!!" :#"Please be patient while we are downloading image for you"];
#try{
DownloadImage *downLoadImge =[[DownloadImage alloc] init];
downLoadImge.delegate=self;
[downLoadImge getImage:[self.allUrlArray objectAtIndex:self.initialImageViewCounter]];
}
#catch (NSException *e) {
NSLog(#"callDownloadImageAPI exception %#",[e description]);
[HUD hide:YES];
}
[pool release];
}
This method download 1 image at a time and send UIImage to its delegate
//Implementation of DownloadImage.h and .m
#protocol DownloadImageDelegate
#required
- (void)messageFormServerWithImage:(UIImage*)imageFromSever;
- (void)gettingImageFailed :(NSString*)errorDesc;
#end
#interface DownloadImage : NSObject
#property(strong) NSURLConnection* connection;
#property(weak) id<DownloadImageDelegate> delegate;
#property(strong) NSMutableData* data;
-(void)getImage:(NSString *)imageUrl;
//DownloadImage.m
-(void)getImage:(NSString *)imageUrl{
#autoreleasepool {
[[NSURLCache sharedURLCache] removeAllCachedResponses];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:imageUrl]cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:60];
self.connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
}
}
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {
#autoreleasepool {
NSLog(#"connectionDidFinishLoading");
self.connection=nil;
if( self.data == nil) {
return;
}
// NSString* jsonStr = [[NSString alloc] initWithData:self.data encoding:NSASCIIStringEncoding];
UIImage *img=[UIImage imageWithData:self.data];
// NSArray *messages_json = [parser objectWithString:jsonStr error:nil];
[self.delegate messageFormServerWithImage:img];
self.data = nil;
img= nil;
}
}
Other delegates of NSUrlConnections are implemented but I am not putting it here .
Once this image is returned i am setting this image to scrollview and displaying it and deleting the previous image from scrollview.
More Info:-
Just to verify i commented out setting image to scrollview and just downloaded images on each swipe but still it crashes around 30 images
Surprisingly I am using same class DownloadImage.h and .m to download image at other places in the same work and it work awesome even with 500images .
I am testing in iPod Touch and I checked the memory utilised remain between 12-14mb(never exceed this)
Please help me out guys,let me know if you need more detail.
Its crashing because all the images are being stored in virtual memory, you need to be caching them and then loading them back into memory when the user actually views them.
Try also setting your image objects to nil after they have been cached or are not needed.
In your class I would also recommend using the didReceiveMemoryWarning method and release some of your images from memory when this is called.
Related
I am trying to create a loose version of LazyTabelImages using storyboard and JSON. in ViewDidLoad on my main TableViewController, I start an NSURLConnection to get the JSON data, but my cells do not load until after the connection is completed. I want the same behavior that LazyTableImages has, where the cells load as blanks, but then have the information filled in (reload the table data). I can duplicate this if I do not use storyboard, as LazyTables does not use storyboard, but that is not an option.
I have looked through LazyTableImages to try to find the solution, but storyboard make a big difference (to me anyway).
Is there a simple way to get the cells to load as blanks? For example, if the device has no internet, I still want my TableView to show up, and I will put a custom message in the cell.
Code:
The part of my viewDidLoad where I initialize the connection....
NSURLRequest *urlrequest = [NSURLRequest requestWithURL:[NSURL URLWithString:serverURL]];
self.dataConnection = [[NSURLConnection alloc] initWithRequest:urlrequest delegate:self];
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
connectionDidFinnishLoading...
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//ListData below is an array that my data received (JSON) is loaded into. It is then passed to getTableData.
self.dataConnection = nil;
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self performSelectorOnMainThread:#selector(getTableData:) withObject:ListData waitUntilDone:YES];
});
}
getTableData...
-(void)getTableData:(NSData *)jsonData
{
NSError *error = nil;
arrayEntries = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableLeaves error:&error];
for (int x = 0; x < arrayEntries.count; x++)
{
NSMutableDictionary *dic = [arrayEntries objectAtIndex:x];
//ARecord is a class just like in LazyTableImages that creates objects to keep the icons/data together. The ARecords are loaded into the TableView
ARecord *arecord = [[ARecord alloc] init];
NSString *title = [dic objectForKey:#"title"];
NSString *subt = [dic objectForKey:#"subtitle"];
NSString *url = [dic objectForKey:#"image_URL"];
arecord.Icon = nil;
arecord.URL = url;
arecord.Name = title;
arecord.title = subt;
//this is where I load an array full of the arecord objects.
[array addObject:arecord];
}
[self.tableView reloadData];
}
I've done something similar. In viewDidLoad: I set the array for table data to a few objects of [NSNull null] for however many blank rows I want to show while the data is downloading. In cellForRowAtIndexPath: I check if [self.arrayOfTableData objectAtIndex:indexPath.row] = [NSNull null]. If so return a "blank" cell, otherwise load the cell with ARRecrod data.
Then when the URL completes, replace the array of NSNulls with array of your ARRecords.
I do this with two objects. First, I have an image fetcher class that downloads data asynchronously and notifies a delegate when it's complete. Then I have an image view class that implements the fetcher's delegate methods. So something like:
#implementation AsyncImageFetcher
-(id)initWithURL:(NSURL *)aURL andDelegate:(id<SomeProtocol>)aDelegate{
//...
NSURLRequest *req = [NSURLRequest requestWithURL:aURL];
//Note that NSURLConnection retains its delegate until the connection
//terminates! See comments in MyImageView below.
[NSURLConnection connectionWithRequest:req delegate:self];
//...
}
//Implement standard connection delegates here. The important part is:
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
// ...
UIImage *anImage = [self decodeDownloadedDataIntoAnImage];
if([[self delegate] respondsToSelector:#selector(imageFetcher:didFetchImage:)]){
[[self delegate] imageFetcher:self didFetchImage:anImage];
}
//...
}
#end
Then I subclass UIImageView or UIView or something (depending on how flexible you need to be) to implement the delegate protocol and fire off the fetcher:
#implementation MyImageView
-(id)initWithURL:(NSURL *)aURL andPlaceHolderImage:(UIImage *)aPlaceHolder{
//...
[self setImage:aPlaceHolder];
//Note we don't assign this to an ivar or retain it or anything.
//That's ok because the NSURLConnection inside the fetcher actually
//retains the fetcher itself. So it will live until the connection
//terminates -- which is exactly what we want. Thus we disable
//CLANG's noisy warnings.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-value"
[[AsyncImageFetcher alloc] initWithURL:aURL andDelegate:self];
#pragma clang diagnostic pop
return self;
}
-(void)imageFetcher:(MCMAsyncImageFetcher *)anImageFetcher didFetchImage:(UIImage *)anImage{
[self setImage:anImage];
}
#end
In your specific case, you'd just set a MyImageView as your cell's imageView in -tableView:cellForRowAtIndexPath:, passing reasonable values for its placeholder and URL, of course.
Since I haven't see your code, I just give my suggestion here:
- (void)viewDidLoad
{
[super viewDidLoad];
dispatch_queue_t queue = dispatch_queue_create(NULL, NULL);
dispatch_async(queue, ^{
//add your connection code here
//parse the json and store the data
//
dispatch_async(dispatch_get_main_queue(), ^{
//here to reload your table view again,
//since UI related method should run on main thread.
[YOUR_TABLEVIEW reloadData];
});
});
[YOUR_TABLEVIEW reloadData];
}
Note: Make sure your tableview in storyboard has connected to that in code! Hope it helps!
I have an app that needs to download a sound file in order to work correctly.
I am using NSURLConnection asynchronously to download my file which is over 20Mb in size.
I placed a progressBarView in order to track the percentage of the downloading and I am using the delegate methods of NSUrlConnection as suggested by Apple.
NSURLRequest *theRequest=[NSURLRequest requestWithURL:soundFileURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20.0];
// create the connection with the request
// and start loading the data
NSURLConnection *theConnection;
theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
//[theConnection cancel];
//[theConnection start];
if (theConnection) {
// Create the NSMutableData that will hold
// the received data
// receivedData is declared as a method instance elsewhere
receivedData=[[NSMutableData data] retain];
} else {
// inform the user that the download could not be made
}
and delegate methods
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
[receivedData appendData:data];
}
and So ...
When I start downloading, the interface hangs from time to time and the progressView hangs as well.
One notable thing, and maybe another question:
I disabled the user interface so the user has to wait until the download finishes and, of course, I give him a message to tell him that.
Would Apple reject my app for that? I am terribly worried about that
Thank you for reading my question :)
NSUrlConnection send events of NSURLConnectionDelegate to main thread by default. You should create new pool and runloop for this connection and be sure that it processed in background. Here are the example of downloading images in background. It using modified NSOperationQueue and NSOperation but you can easy modify it for downloading your file. LinkedImageFetcher on developer.apple.com
//1 First allocate NSOperationQueue object and set number of concurrent operations to execute at a time
NSOperationQueue *thumbnailQueue = [[NSOperationQueue alloc] init];
thumbnailQueue.maxConcurrentOperationCount = 3;
// load photo images in the background
__weak BHCollectionViewController *weakSelf = self;
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
UIImage *image = [photo image];
dispatch_async(dispatch_get_main_queue(), ^{
// then set them via the main queue if the cell is still visible.
cell.imageView.image = image;
}
});
}];
operation.queuePriority = (indexPath.item == 0) ?
NSOperationQueuePriorityHigh : NSOperationQueuePriorityNormal;
[thumbnailQueue addOperation:operation];
Create Photo class of NSObject and add below method
- (UIImage *)image
{
if (!_image && self.imageURL) {
NSData *imageData = [NSData dataWithContentsOfURL:self.imageURL];
UIImage *image = [UIImage imageWithData:imageData scale:[UIScreen mainScreen].scale];
_image = image;
}
return _image;
}
I need to download an image from the web and display it in an ImageView. Presently I am using SDWebImage (It is an asynchronous image downloader with cache support, with a UIImageView category).
But it crashes when I click the back button and forward button (when I try to go back and forth of the view repeatedly). Anyway this happens very rarely, but I need to get rid of this bug. Is there any other library (that does not use private API's) that I could use in my project?
Yes. You can user other libary. I've already implemented that using AsyncImageView which is inherited from UIImageView. What it does is it stores images in Cache memory fetched from a url and whenever you need to load image from the same URL again it will simply load it from the cache memory saving a lot of time.
Just follow the link for implementing that:
https://github.com/nicklockwood/AsyncImageView#readme
http://www.markj.net/iphone-asynchronous-table-image/
Please have a look at the image showing the technique I've implemented. It lets you do other activity while images are loading.:
NSURLConnection provides asynchronous downloading and is built into iOS.
I think that the bug that you describe may occur because when you "go back" release some objects that can be delegates of connections that are still running. For avoid crashes, you should cancel the connections before release or dealloc any object that could be a delegate of a running connection.
Another alternative for image async download is http://allseeing-i.com/ASIHTTPRequest/ .
I personally use the built in Grand Central Dispatch feature in iOS to download images from the server asynchronously.
Below is a code I used to fetch photos from Flickr in one of my apps.
In your image/photo class, have a function that is something like this:
- (void)processImageDataWithBlock:(void (^)(NSData *imageData))processImage
{
NSString *url = self.imageURL;
dispatch_queue_t callerQueue = dispatch_get_current_queue();
dispatch_queue_t downloadQueue = dispatch_queue_create("Photo Downloader", NULL);
dispatch_async(downloadQueue, ^{
NSData *imageData = *insert code that fetches photo from server*;
dispatch_async(callerQueue, ^{
processImage(imageData);
});
});
dispatch_release(downloadQueue);
}
In your Photo View Controller, you can call this function like this:
- (void)viewWillAppear:(BOOL)animated
{
[spinner startAnimating];
[self.photo processImageDataWithBlock:^(NSData *imageData) {
if (self.view.window) {
UIImage *image = [UIImage imageWithData:imageData];
imageView.image = image;
imageView.frame = CGRectMake(0, 0, image.size.width, image.size.height);
scrollView.contentSize = image.size;
[spinner stopAnimating];
}
}];
}
Check out EGOImageLoading by enormego for caching images.
It Works just like UIImageView and lets you download images from HTTP asynchronously and also its easy to integrate
//JImage.h
#import <Foundation/Foundation.h>
#interface JImage : UIImageView {
NSURLConnection *connection;
NSMutableData* data;
UIActivityIndicatorView *ai;
}
-(void)initWithImageAtURL:(NSURL*)url;
#property (nonatomic, retain) NSURLConnection *connection;
#property (nonatomic, retain) NSMutableData* data;
#property (nonatomic, retain) UIActivityIndicatorView *ai;
#end
//JImage.m
#import "JImage.h"
#implementation JImage
#synthesize ai,connection, data;
-(void)initWithImageAtURL:(NSURL*)url {
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
[self setContentMode:UIViewContentModeScaleToFill];
if (!ai){
[self setAi:[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge]];
[ai startAnimating];
[ai setFrame:CGRectMake(27.5, 27.5, 20, 20)];
[ai setColor:[UIColor blackColor]];
[self addSubview:ai];
}
NSURLRequest* request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60];
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
}
- (void)connection:(NSURLConnection *)theConnection didReceiveData:(NSData *)incrementalData {
if (data==nil) data = [[NSMutableData alloc] initWithCapacity:5000];
[data appendData:incrementalData];
NSNumber *resourceLength = [NSNumber numberWithUnsignedInteger:[data length]];
NSLog(#"resourceData length: %d", [resourceLength intValue]);
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSLog(#"Connection error...");
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
[ai removeFromSuperview];
}
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection
{
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
[self setImage:[UIImage imageWithData: data]];
[ai removeFromSuperview];
}
#end
//Include the definition in your class where you want to use the image
-(UIImageView*)downloadImage:(NSURL*)url:(CGRect)frame {
JImage *photoImage=[[JImage alloc] init];
photoImage.backgroundColor = [UIColor clearColor];
[photoImage setFrame:frame];
[photoImage setContentMode:UIViewContentModeScaleToFill];
[photoImage initWithImageAtURL:url];
return photoImage;
}
//How to call the class
UIImageView *imagV=[self downloadImage:url :rect];
//you can call the downloadImage function in looping statement and subview the returned imageview.
//it will help you in lazy loading of images.
//Hope this will help
I know this is a very old thread but recently i had a lot of random crashes with SDWebImage, so i had to implement my own lazy loading and caching mechanism. It works pretty well, i just haven't tested it in heavy load cases. So here is the .h and .m files followed by the way i use it :
// UIImageView+CustomCache.h
#interface UIImageView(CustomCache)
-(void)startAsyncDownload:(UIImage*)placeHolderImage imageUrlString:(NSString*)imageUrlString;
#end
// UIImageView+CustomCache.m
#import "UIImageView+CustomCache.h"
#implementation UIImageView(CustomCache)
-(void)startAsyncDownload:(UIImage*)placeHolderImage imageUrlString:(NSString*)imageUrlString{
self.image = placeHolderImage;
[NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:
[NSURL URLWithString:imageUrlString]] queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionHandler){
#autoreleasepool {
if (connectionHandler != nil) {
NSLog(#"error in downloading description %#",connectionHandler.localizedDescription);
} else {
ImagesCacheHandler *ref = [ImagesCacheHandler new];
UIImage *imageFromData = [[UIImage alloc] initWithData:data];
if (imageFromData != NULL && imageFromData != nil && data.length > 0) {
self.image = imageFromData;
//custom store to sqlite
[ref archiveImage:imageUrlString imageData:data moc:[ref fetchContext]];
}
}
}
}];
}
#end
And in my table view i use (i import of course UIImageView+CustomCache.h)
UIImageView *imageViewToLazyLoad = (UIImageView*)[cell viewWithTag:1];
[imageViewToLazyLoad startAsyncDownload:[UIImage imageNamed#"palce_Holder_Image_name"] imageUrlString:imageUrl];
I personally prefer using NSURLConnection sendSynchronousRequest and putting a GCD wrapper around it. Keeps everything neat and tidy.
I would like to add to UIImageView the capacity to set an image with an url. As result I would like to do something like.
[anImageView setImageWithContentAtUrl:[NSURL URLWithString:#"http://server.com/resource.png"]];
So I created a category (code below).
NSString *kUserInfoImageViewKey = #"imageView";
NSString *kUserInfoActivityIndicatorKey = #"activityIndicator";
#implementation UIImageView (asynchronous)
#pragma mark -
- (void)setImageWithContentAtUrl:(NSURL *)imageUrl andActivityIndicator:(UIActivityIndicatorView *)activityIndicatorOrNil {
[activityIndicatorOrNil startAnimating];
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setValue:self forKey:kUserInfoImageViewKey];
[dict setValue:activityIndicatorOrNil forKey:kUserInfoActivityIndicatorKey];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:imageUrl];
request.delegate = self;
request.userInfo = dict;
[dict release];
[request startAsynchronous];
}
#pragma mark -
#pragma mark private
- (void)requestFinished:(ASIHTTPRequest *)aRequest {
// get concerned view from user info
NSDictionary *dictionary = aRequest.userInfo;
UIImageView *imageView = (UIImageView *)[dictionary valueForKey:kUserInfoImageViewKey];
UIActivityIndicatorView *activityIndicator = (UIActivityIndicatorView *) [dictionary valueForKey:kUserInfoActivityIndicatorKey];
[activityIndicator stopAnimating];
NSData *responseData = [aRequest responseData];
UIImage * image = [[UIImage alloc] initWithData:responseData];
imageView.image = image;
[image release];
}
- (void)requestFailed:(ASIHTTPRequest *)request {
}
An ASIHTTPRequest is created and launched with the image as delegate. I think there is a risk if image is deallocated before ASIHTTPRequest return a result.
So, maybe adding a retain in setImageWithContentAtUrl: and adding a release in requestFinished: and requestFailed: but I'm not very confident.
How is it possible to do such things ?
Regards,
Quentin
Quentin,
I regularly use ASIHTTPRequest for asynchronous calls, so I know where you're coming from here. Also, it's a pain to set up for the first time, but did you know that Three20 library's TTImageView (I think that's it) already does what you are trying to do? It will even cache the image locally so you don't have to load it every time. Anyway.
Your worry is correct: ASIHTTPRequest is a wrapper on an NSOperation object (it's actually a subclass), so the NSOperationQueue will retain ASIHTTPRequest as long as the request is active.
If your user changes the view (say, on a nav bar controller), which then deallocs your UIImageView, your code may crash when it tries to call back to the delegate. So, when you dealloc your image view, it's better to hold on to a reference to the request and then cancel it.
Rather than a category, this may be one of those times where subclassing is better - because you'd want to overwrite the dealloc method (this is how I've handled this issue).
First, add this property to your subclass:
#property (nonatomic, retain) ASIHTTPRequest *request;
Then add this line to your method so you can hold on to it:
self.request = request;
And finally, in your ASIHTTPRequest delegate methods, destroy the reference:
self.request = nil;
Then your dealloc could look like this:
- (void) dealloc
{
if (self.request)
{
// Cancels the NSOperation so ASIHTTPRequest doesn't call back to this
[self.request cancel];
}
[request release];
[super dealloc]
}
I have a method that asynchronously downloads images. If the images are related to an array of objects (a common use-case in the app I'm building), I want to cache them. The idea is, I pass in an index number (based on the indexPath.row of the table I'm making by way through), and I stash the image in a static NSMutableArray, keyed on the row of the table I'm dealing with.
Thusly:
#implementation ImageDownloader
...
#synthesize cacheIndex;
static NSMutableArray *imageCache;
-(void)startDownloadWithImageView:(UIImageView *)imageView andImageURL:(NSURL *)url withCacheIndex:(NSInteger)index
{
self.theImageView = imageView;
self.cacheIndex = index;
NSLog(#"Called to download %# for imageview %#", url, self.theImageView);
if ([imageCache objectAtIndex:index]) {
NSLog(#"We have this image cached--using that instead");
self.theImageView.image = [imageCache objectAtIndex:index];
return;
}
self.activeDownload = [NSMutableData data];
NSURLConnection *conn = [[NSURLConnection alloc]
initWithRequest:[NSURLRequest requestWithURL:url] delegate:self];
self.imageConnection = conn;
[conn release];
}
//build up the incoming data in self.activeDownload with calls to didReceiveData...
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(#"Finished downloading.");
UIImage *image = [[UIImage alloc] initWithData:self.activeDownload];
self.theImageView.image = image;
NSLog(#"Caching %# for %d", self.theImageView.image, self.cacheIndex);
[imageCache insertObject:image atIndex:self.cacheIndex];
NSLog(#"Cache now has %d items", [imageCache count]);
[image release];
}
My index is getting through okay, I can see that by my NSLog output. But even after my insertObject: atIndex: call, [imageCache count] never leaves zero.
This is my first foray into static variables, so I presume I'm doing something wrong.
(The above code is heavily pruned to show only the main thing of what's going on, so bear that in mind as you look at it.)
You seem to never initialize the imageCache and probably got lucky with it having the value 0. The initialization would best be done in the class' initialization, e.g.:
#implementation ImageDownloader
// ...
+(void)initialize {
imageCache = [[NSMutableArray alloc] init];
}
// ...