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POVery jerky scrolling NSTableView
 

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  1. POVery jerky scrolling NSTableView
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    <p>I have an NSScrollView which contains an NSTableView, this has 3 columns, 1 of which has a custom view in it via TableCellView.</p> <p>To load images into this cell via background processes, i have subclassed the cell using the below code. However the scrolling is really jerky, i am wondering if there is any way to optimise this, the images are not very large, 48x48, and are being displayed at 51x51.</p> <p>I suspect the fact that a fetch request is being used for each row is probably not very efficient, and i need to find a way to set an NSArray each time the view is changed that is current, and use that instead. But i was wanting to get this as efficient as possible first.</p> <pre><code>- (NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row { // Get a new ViewCell NSTableCellView *cellView = [tableView makeViewWithIdentifier:tableColumn.identifier owner:self]; //Identify the correct column if( [tableColumn.identifier isEqualToString:@"userLogo"] ) { NSFetchRequest *request = [[NSFetchRequest alloc] init]; //Set predicate and filter for New tweets page if ([self.currentTwitterView isEqualToString:@"new"]) { NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"(approved == NO) AND (tweetDeleted == NO) AND (scheduledTweet == NO)"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"postDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; //Set filter and predicate for the Approved tweets page } else if ([self.currentTwitterView isEqualToString:@"approved"]){ NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"(approved == YES) AND (tweetDeleted == NO) AND (scheduledTweet == NO)"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"approvedDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; //Set filter and preicate for the Deleted tweets page } else if ([self.currentTwitterView isEqualToString:@"deleted"]){ NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"tweetDeleted == YES"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"deletedDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; //Set filter and preicate for the Deleted tweets page } else if ([self.currentTwitterView isEqualToString:@"scheduled"]){ NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"scheduledTweet == YES"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"scheduledDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; } //Setup the Request [request setEntity:[NSEntityDescription entityForName:@"Tweet" inManagedObjectContext:_managedObjectContext]]; //Assign the predicate to the fetch request NSError *error = nil; //Create an array from the returned objects NSArray *fetchedObjects = [_managedObjectContext executeFetchRequest:request error:&amp;error]; Tweet *selectedTweet = [fetchedObjects objectAtIndex:row]; cellView.imageView.image = nil; dispatch_async(dispatch_queue_create("getAsynchronIconsGDQueue", NULL), ^{ NSURL *url = [NSURL URLWithString:selectedTweet.avatarUrl]; NSImage *image = [[NSImage alloc] initWithContentsOfURL:url]; cellView.imageView.image = image; }); [cellView setWantsLayer:YES]; return cellView; } [cellView setWantsLayer:YES]; return cellView; } </code></pre> <p>Thanks</p> <p>Gareth</p> <p><strong>EDIT 1</strong></p> <p>Ok have tried implementing AFImageRequest, and performance is worst, and also i seem to get getting multiple copies of the same image/the wrong image in various rows.</p> <p>Here is the code i am using.</p> <pre><code>@synthesize profileImage = _profileImage; + (NSOperationQueue *)sharedProfileImageRequestOperationQueue { static NSOperationQueue *_sharedProfileImageRequestOperationQueue = nil; static dispatch_once_t onceToken; dispatch_once(&amp;onceToken, ^{ _sharedProfileImageRequestOperationQueue = [[NSOperationQueue alloc] init]; [_sharedProfileImageRequestOperationQueue setMaxConcurrentOperationCount:8]; }); return _sharedProfileImageRequestOperationQueue; } //Load the image into the table - (NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row { // Get a new ViewCell NSTableCellView *cellView = [tableView makeViewWithIdentifier:tableColumn.identifier owner:self]; //Identify the correct column if( [tableColumn.identifier isEqualToString:@"userLogo"] ) { NSFetchRequest *request = [[NSFetchRequest alloc] init]; //Set predicate and filter for New tweets page if ([self.currentTwitterView isEqualToString:@"new"]) { NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"(approved == NO) AND (tweetDeleted == NO) AND (scheduledTweet == NO)"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"postDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; //Set filter and predicate for the Approved tweets page } else if ([self.currentTwitterView isEqualToString:@"approved"]){ NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"(approved == YES) AND (tweetDeleted == NO) AND (scheduledTweet == NO)"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"approvedDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; //Set filter and preicate for the Deleted tweets page } else if ([self.currentTwitterView isEqualToString:@"deleted"]){ NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"tweetDeleted == YES"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"deletedDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; //Set filter and preicate for the Deleted tweets page } else if ([self.currentTwitterView isEqualToString:@"scheduled"]){ NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"scheduledTweet == YES"]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"scheduledDate" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, nil]; [request setPredicate:testForTrue]; [request setSortDescriptors:sortDescriptors]; } //Setup the Request [request setEntity:[NSEntityDescription entityForName:@"Tweet" inManagedObjectContext:_managedObjectContext]]; //Assign the predicate to the fetch request NSError *error = nil; //Create an array from the returned objects NSArray *fetchedObjects = [_managedObjectContext executeFetchRequest:request error:&amp;error]; Tweet *selectedTweet = [fetchedObjects objectAtIndex:row]; NSURL *url = [NSURL URLWithString:selectedTweet.avatarUrl]; /*cellView.imageView.image = nil; dispatch_async(dispatch_queue_create("getAsynchronIconsGDQueue", NULL), ^{ NSURL *url = [NSURL URLWithString:selectedTweet.avatarUrl]; NSImage *image = [[NSImage alloc] initWithContentsOfURL:url]; cellView.imageView.image = image; }); */ _avatarImageRequestOperation = [AFImageRequestOperation imageRequestOperationWithRequest:[NSURLRequest requestWithURL:url] success:^(NSImage *image) { cellView.imageView.image = self.profileImage; _avatarImageRequestOperation = nil; [[NSNotificationCenter defaultCenter] postNotificationName:kUserProfileImageDidLoadNotification object:self userInfo:nil]; }]; [_avatarImageRequestOperation setCacheResponseBlock:^NSCachedURLResponse *(NSURLConnection *connection, NSCachedURLResponse *cachedResponse) { return [[NSCachedURLResponse alloc] initWithResponse:cachedResponse.response data:cachedResponse.data userInfo:cachedResponse.userInfo storagePolicy:NSURLCacheStorageAllowed]; }]; [[[self class] sharedProfileImageRequestOperationQueue] addOperation:_avatarImageRequestOperation]; //cellView.imageView.image = self.profileImage; //[cellView setWantsLayer:YES]; return cellView; } </code></pre>
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    1. COI haven't looked at this very carefully (rushed today), but would like to suggest something. What I tend to do in this case is use a background thread to load the first few (say 10 or so) images and add them to the table view cells. Then I use an NSTimer to load a few more every second or so. This allows the pacing to spread itself out more. After the images are loaded I cache them so they are available faster in the future. You might want to consider doing something similar. I also will max out what it can load if there are a lot of cells.
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