UITableView cell shows same images on fast scrolling - ios

Question

I am creating the iPhone app which shows the app icons & app names in table view.
First time i download the images in user document directory & then make entry in dictionary [value - image stored document directory path & key is image json URL], for showing image in cell first i checked the image is already download or not.
If downloaded, then show the local image which stored on document directory and if not download it.
If i Scrolled normally, cell shows the rights images & if i scrolled it fast, cell shows the same images instead of different.
// code for displaying images
-(void)refreshViews
{
self.appLabelName.text = _applicationObject.name;
self.appLabelName.font = [UIFont fontWithName:#"Helvetica-Bold" size:17];
self.detailTextLabel.text = _applicationObject.artistName;
self.detailTextLabel.font = [UIFont fontWithName:#"Helvetica" size:14];
NSString *appIconStoredPath = [appDelgate.saveAppIconURLAndPathInFile valueForKey:_applicationObject.iconURL];
_appIcon.image = [UIImage imageWithContentsOfFile:appIconStoredPath];
if(!_appIcon.image && appDelgate.hasInternetConnection)
{
[self downloadAppIconsInDirectory];
}
}
// code for download image
-(void)downloadAppIconsInDirectory
{
NSURL *downloadURL = [NSURL URLWithString:_applicationObject.iconURL];
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig delegate:nil delegateQueue:nil];
__weak ApplicationCell* weakSelf = self;
dispatch_async(queue, ^{
downloadTask = [session downloadTaskWithURL:downloadURL completionHandler:^(NSURL *location, NSURLResponse *respone, NSError *error)
{
NSString *iconName = [location lastPathComponent];
NSMutableString *changeIconName = [[NSMutableString alloc] init];
changeIconName = [iconName mutableCopy];
[changeIconName setString:_applicationObject.bundleId];![enter image description here][1]
NSString *appIconDirectory = [[documentsDirectoryForAppIcons absoluteString] stringByAppendingPathComponent:#"appIcons"];
destinationUrlForAppIcons = [[NSURL URLWithString:appIconDirectory] URLByAppendingPathComponent:changeIconName];
NSError *error1;
BOOL status = [appIconFileManager copyItemAtURL:location toURL:destinationUrlForAppIcons error:&error1];
if (status && !error1)
{
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf refreshViews];
});
[appDelgate.saveAppIconURLAndPathInFile setValue:destinationUrlForAppIcons.path forKey:_applicationObject.iconURL];
NSString *dictSavedFilePath = [appDelgate.documentDirectoryPath stringByAppendingPathComponent:#"IconURLsAndPaths.plist"];
dispatch_async(queue, ^{
[appDelgate.saveAppIconURLAndPathInFile writeToFile:dictSavedFilePath atomically:YES];
});
}
}];
[downloadTask resume];
});
}

Answer 1

As it shows, there is no error in code. This means you are priority for queues is wrong. Image must be downloaded before scrolling. As you scroll your view slow, image gets enough time to be downloaded. This means you change your code to this and try ;)
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration
defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig delegate:nil
delegateQueue:nil];
__weak ApplicationCell* weakSelf = self;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
downloadTask = [session downloadTaskWithURL:downloadURL completionHandler:^(NSURL *location,
{
NSString *iconName = [location lastPathComponent];
NSMutableString *changeIconName = [[NSMutableString alloc] init];
changeIconName = [iconName mutableCopy];
[changeIconName setString:_applicationObject.bundleId];![enter image description here]
[1]
NSString *appIconDirectory = [[documentsDirectoryForAppIcons absoluteString]
stringByAppendingPathComponent:#"appIcons"];
destinationUrlForAppIcons = [[NSURL URLWithString:appIconDirectory]
URLByAppendingPathComponent:changeIconName];
NSError *error1;
BOOL status = [appIconFileManager copyItemAtURL:location
toURL:destinationUrlForAppIcons error:&error1];
if (status && !error1)
{
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf refreshViews];
});
[appDelgate.saveAppIconURLAndPathInFile
setValue:destinationUrlForAppIcons.path forKey:_applicationObject.iconURL];
NSString *dictSavedFilePath = [appDelgate.documentDirectoryPath
stringByAppendingPathComponent:#"IconURLsAndPaths.plist"];
dispatch_async(queue, ^{
[appDelgate.saveAppIconURLAndPathInFile writeToFile:dictSavedFilePath
atomically:YES];
});
}
}];
[downloadTask resume];
});
}

Answer 2

replace your refreshViews method with this
-(void)refreshViews
{
self.appLabelName.text = _applicationObject.name;
self.appLabelName.font = [UIFont fontWithName:#"Helvetica-Bold" size:17];
self.detailTextLabel.text = _applicationObject.artistName;
self.detailTextLabel.font = [UIFont fontWithName:#"Helvetica" size:14];
_appIcon.image = nil;
NSString *appIconStoredPath = [appDelgate.saveAppIconURLAndPathInFile valueForKey:_applicationObject.iconURL];
_appIcon.image = [UIImage imageWithContentsOfFile:appIconStoredPath];
if(!_appIcon.image && appDelgate.hasInternetConnection)
{
[self downloadAppIconsInDirectory];
}
}
Its load previous image because your tableview reuse the cell so the imageview also reusing which hold the previous image. so you have to do nil this image