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POUITableView with complex cells is slow and laggy
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copied!<p>I've almost finished my app and everything seems to work but the main view.<br> It's an <code>UIViewController</code> with an embedded <code>UITableView</code>.<br> I'm using Parse as the backend, and I get an array of the objects I need in my <code>viewDidLoad</code> method.</p> <p>Each cell contains some data that I'm fetching in the <code>tableView:cellForRowAtIndexPath</code> and I'm afraid that this is the reason why my table view is so laggy, but I don't know how to fetch the data I need for each object in my array without having the <code>indexPath.row</code> number.</p> <p>I've already made each cell element "opaque" as suggested in other answers.</p> <p>This is my code, any help would be greatly appreciated:</p> <pre><code>- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"cellHT"; CellHT *cell = (CellHT *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (!cell) { cell = [[CellHT alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; } // self.hH is an NSArray containing all the objects NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; cell.lblTitle.text = [self.hH[indexPath.row] objectForKey:@"title"]; cell.lblVenueName.text = [self.hH[indexPath.row] objectForKey:@"venueName"]; cell.lblDistance.text = NSLocalizedString(@"Distance from you", nil); self.geo = [self.hH[indexPath.row] objectForKey:@"coordinates"]; // the formatters are initialized in the viewDidLoad: method self.formatData = [NSDateFormatter dateFormatFromTemplate:@"dd/MM" options:0 locale:[NSLocale currentLocale]]; [self.formatterData setDateFormat:self.formatData]; self.formatOra = [NSDateFormatter dateFormatFromTemplate:@"j:mm" options:0 locale:[NSLocale currentLocale]]; [self.formatterOra setDateFormat:self.formatOra]; self.dal = NSLocalizedString(@"from", nil); self.ore = NSLocalizedString(@"at", nil); CLLocation *vLoc = [[CLLocation alloc] initWithLatitude:self.geo.latitude longitude:self.geo.longitude]; CLLocation *user = [[CLLocation alloc] initWithLatitude:self.userGeo.latitude longitude:self.userGeo.longitude]; CLLocationDistance distance = [user distanceFromLocation:venueLoc]; if ([[prefs objectForKey:@"unit"] isEqualToString:@"km"]) { cell.lblDist.text = [NSString stringWithFormat:@"%.1f Km", distance /1000]; } else { cell.lblDist.text = [NSString stringWithFormat:@"%.1f Miles", distance /1609]; } // compare the object's starting date with the current date to set some images in the cell NSComparisonResult startCompare = [[self.hH[indexPath.row] objectForKey:@"startDate"] compare: [NSDate date]]; if (startCompare == NSOrderedDescending) { cell.quad.image = [UIImage imageNamed:@"no_HT"]; cell.lblStartTime.textColor = [UIColor redColor]; } else { cell.quad.image = [UIImage imageNamed:@"yes_HT"]; cell.lblStartTime.textColor = [UIColor colorWithRed:104.0/255.0 green:166.0/255.0 blue:66.0/255.0 alpha:1.0]; } NSString *dataInizio = [NSString stringWithFormat:@"%@ %@ %@ %@", self.dal, [self.formatterData stringFromDate:[self.hH[indexPath.row] objectForKey:@"startDate"]], self.ore, [self.formatterOra stringFromDate:[self.hH[indexPath.row] objectForKey:@"endDate"]]]; cell.lblStartTime.text = dataInizio; PFObject *cat = [self.hH[indexPath.row] objectForKey:@"catParent"]; NSString *languageCode = [[NSLocale preferredLanguages] objectAtIndex:0]; if ([languageCode isEqualToString:@"it"]) { cell.lblCategory.text = [cat objectForKey:@"nome_it"]; } else if ([languageCode isEqualToString:@"es"]) { cell.lblCategory.text = [cat objectForKey:@"nome_es"]; } else { cell.lblCategory.text = [cat objectForKey:@"nome_en"]; } //getting the image data from the Parse PFFile PFFile *theImage = [self.hH[indexPath.row] objectForKey:@"photo"]; [theImage getDataInBackgroundWithBlock:^(NSData *data, NSError *error) { if (!error) { cell.cellImageView.image = [UIImage imageWithData:data]; } }]; //getting the cell object's owner and his profile PFUser *usr = [self.hH[indexPath.row] objectForKey:@"parent"]; PFQuery *prof = [PFQuery queryWithClassName:@"Profile"]; prof.cachePolicy = kPFCachePolicyCacheThenNetwork; [prof whereKey:@"parent" equalTo:usr]; [prof getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) { if (!error) { //getting the object's rating and the number of votes PFQuery *rateQuery = [PFQuery queryWithClassName:@"Rating"]; [rateQuery whereKey:@"parent" equalTo:object]; [rateQuery getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) { if (!error) { float vote = [[object objectForKey:@"rate"] floatValue]; float temp = ((vote * 2) + 0.5); int tempvote = (int)temp; float roundedVote = (float)tempvote / 2; // drawing the stars number, depending on the rating obtained UIImage *starsImage = [UIImage imageNamed:@"stars"]; UIGraphicsBeginImageContextWithOptions(cell.imgVoto.frame.size, NO, 0); CGPoint starPoint = (CGPoint) { .y = (cell.imgVoto.frame.size.height * (2 * roundedVote + 1)) - (starsImage.size.height) }; [starsImage drawAtPoint:starPoint]; cell.imgVoto.image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); cell.lblVoto.text = [NSString stringWithFormat:@"(%d)", [[object objectForKey:@"voters"] intValue]]; } }]; } }]; return cell; } </code></pre> <p>EDIT: this is the cell code:</p> <pre><code>+ (void)initialize { if (self != [HH class]) { return; } } -(id)initWithCoder:(NSCoder *)aDecoder { if ( !(self = [super initWithCoder:aDecoder]) ) return nil; self.cellImageView.image = [UIImage imageNamed:@"icona_foto"]; self.cellImageView.contentMode = UIViewContentModeScaleToFill; self.formatterData = [[NSDateFormatter alloc] init]; self.formatData = [[NSString alloc] init]; self.formatterOra = [[NSDateFormatter alloc] init]; self.formatOra = [[NSString alloc] init]; self.formatData = [NSDateFormatter dateFormatFromTemplate:@"dd/MM" options:0 locale:[NSLocale currentLocale]]; [self.formatterData setDateFormat:self.formatData]; self.formatOra = [NSDateFormatter dateFormatFromTemplate:@"j:mm" options:0 locale:[NSLocale currentLocale]]; [self.formatterOra setDateFormat:self.formatOra]; self.lblVoto.text = @"(0)"; return self; } </code></pre> <p>SECOND EDIT: this is the code in the <code>viewDidLoad</code> method:</p> <pre><code> PFQuery *hours = [PFQuery queryWithClassName:@"HH"]; hours.cachePolicy = kPFCachePolicyCacheThenNetwork; // here I'm making lots of query constraints that I'll not include [hours findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) { if (!error) { self.objectsNumber = objects.count; self.hH = [[NSArray alloc] initWithArray:objects]; } }]; [self.tableView reloadData]; } </code></pre>

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