UITableView with Json file, loading images to cell disappear - ios

Question

I am using asyncimageview classes nicely provided by: http://www.markj.net/iphone-asynchronous-table-image/
I am getting image urls from a json file and loading each image to a cell.
Problem:
When i scroll up, and scroll back down to the same cell, the image reloads (disappears and appears again). I can't figure out why the image keeps reloading? Does anyone have suggestions or a solution to how I could make it stop? Thanks in advance!
// Asks the data source to return a cell to insert in a particular table view location
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
//Gets the current news article
NewsArticle *theCurrentArticle = [self.listofNewsArticles objectAtIndex:[indexPath row]];
//Gets the title from the current article
NSString *theTitle = theCurrentArticle.title;
//Gets the image url
NSString *imageUrl = theCurrentArticle.imageURL;
//Gets the description of the current news article
NSString *theDescription = theCurrentArticle.description;
NewsCustomCell *cell = (NewsCustomCell *)[tableView dequeueReusableCellWithIdentifier:#"NewsContent"];
__block NewsCustomCell *aCell;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
if (cell == nil) {
aCell = (NewsCustomCell *)[tableView dequeueReusableCellWithIdentifier:#"NewsContent"];
} else {
AsyncImageView* oldImage = (AsyncImageView*)
[cell.contentView viewWithTag:999];
[oldImage removeFromSuperview];
}
AsyncImageView *imageView = [[AsyncImageView alloc] initWithFrame:CGRectMake(5, 5, 100, 100)];
imageView.tag = 999;
dispatch_async(dispatch_get_main_queue(), ^{
[imageView loadImageFromURL:[NSURL URLWithString:imageUrl]];
[cell.contentView addSubview:imageView];
cell.titleLabel.text = theTitle;
cell.descriptionLabel.text = theDescription;
cell.imageLabel.contentMode = UIViewContentModeScaleAspectFill;
});
});
return cell;
}
Heres what the current app looks like:
Solution:
Just worked with this class I finally found.
https://github.com/rs/SDWebImage
This handles caching, async downloads. Wish I found this sooner..

Answer 1

I hope you have Write AsyncImageView and ImageCache and ImageCacheObject classes.
Write this code inside cellForRowAtIndexPath:
static NSString *CellIdentifier = #"CellIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
Quest_Forum *Quest_ForumObj=[queArr objectAtIndex:i+indexPath.row];
// NSLog(#"cell for row at... i val.. %d",i+indexPath.row);
for(UIView * view in cell.contentView.subviews){
if([view isKindOfClass:[AsyncImageView class]])
{
// NSLog(#"remove old images");
[view removeFromSuperview];
view = nil;
}
}
AsyncImageView *asyncImageView = nil;
UIImageView *cellImage = (UIImageView *)[cell viewWithTag:1]; // Inside tableview i have taken tableviewcell and given tag 1 to that imageview
asyncImageView = [[AsyncImageView alloc] initWithFrame:cellImage.frame] ;
[asyncImageView loadImageFromURL:Quest_ForumObj.Quest_Image];
asyncImageView.backgroundColor=[UIColor clearColor];
[cell.contentView addSubview:asyncImageView];
UILabel *lblQuest = (UILabel *)[cell viewWithTag:2]; // Given tag 2 to the label inside tableViewCell
lblQuest.text=Quest_ForumObj.Question;
In ImageCacheObject.h
#class ImageCacheObject;
#interface ImageCache : NSObject
{
NSUInteger totalSize; // total number of bytes
NSUInteger maxSize; // maximum capacity
NSMutableDictionary *myDictionary;
}
#property (nonatomic, readonly) NSUInteger totalSize;
-(id)initWithMaxSize:(NSUInteger) max;
-(void)insertImage:(UIImage*)image withSize:(NSUInteger)sz forKey:(NSString*)key;
-(UIImage*)imageForKey:(NSString*)key;
In ImageCacheObject.m
#import "ImageCacheObject.h"
#synthesize totalSize;
-(id)initWithMaxSize:(NSUInteger) max
{
if (self = [super init])
{
totalSize = 0;
maxSize = max;
myDictionary = [[NSMutableDictionary alloc] init];
}
return self;
}
-(void)dealloc // Don't write this method if you are using ARC
{
[myDictionary release];
[super dealloc];
}
-(void)insertImage:(UIImage*)image withSize:(NSUInteger)sz forKey:(NSString*)key
{
// NSLog(#"count of insert image%d",sz);
ImageCacheObject *object = [[ImageCacheObject alloc] initWithSize:sz Image:image];
while (totalSize + sz > maxSize)
{
NSDate *oldestTime;
NSString *oldestKey;
for (NSString *key in [myDictionary allKeys])
{
ImageCacheObject *obj = [myDictionary objectForKey:key];
if (oldestTime == nil || [obj.timeStamp compare:oldestTime] == NSOrderedAscending)
{
oldestTime = obj.timeStamp;
oldestKey = key;
}
}
if (oldestKey == nil)
break; // shoudn't happen
ImageCacheObject *obj = [myDictionary objectForKey:oldestKey];
totalSize -= obj.size;
[myDictionary removeObjectForKey:oldestKey];
}
[myDictionary setObject:object forKey:key];
[object release];
}
-(UIImage*)imageForKey:(NSString*)key
{
ImageCacheObject *object = [myDictionary objectForKey:key];
if (object == nil)
return nil;
[object resetTimeStamp];
return object.image;
}
In ImageCacheObject.h
#interface ImageCacheObject : NSObject
{
NSUInteger size; // size in bytes of image data
NSDate *timeStamp; // time of last access
UIImage *image; // cached image
}
#property (nonatomic, readonly) NSUInteger size;
#property (nonatomic, retain, readonly) NSDate *timeStamp;
#property (nonatomic, retain, readonly) UIImage *image;
-(id)initWithSize:(NSUInteger)sz Image:(UIImage*)anImage;
-(void)resetTimeStamp;
In ImageCacheObject.m
#synthesize size;
#synthesize timeStamp;
#synthesize image;
-(id)initWithSize:(NSUInteger)sz Image:(UIImage*)anImage
{
if (self = [super init])
{
size = sz;
timeStamp = [[NSDate date] retain];
image = [anImage retain];
}
return self;
}
-(void)resetTimeStamp
{
[timeStamp release];
timeStamp = [[NSDate date] retain];
}
-(void) dealloc
{
[timeStamp release];
[image release];
[super dealloc];
}