Slow loading tableview on iPhone with reusable cells

Question

I load the data from Parse.com backend, they send me a solutions for use the reusable cells but now I still have troubles with the loading speed, this is the coding I have in my tableview and I have a Subclass for making up my cells (ExploreStreamCustomCell.m)

    - (ExploreStreamCustomCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
                        object:(PFObject *)object 
{
    static NSString *CellIdentifier = @"ExploreStreamCustomCell";

    ExploreStreamCustomCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[ExploreStreamCustomCell alloc] initWithStyle:UITableViewCellStyleSubtitle 
                                              reuseIdentifier:CellIdentifier];
    }

    // Configure the cell
    cell.listItemTitle.text = [object objectForKey:@"text"];
    cell.checkinsLabel.text = [NSString stringWithFormat:@"%@", [object objectForKey:@"checkins"]];
    cell.descriptionLabel.text = [object objectForKey:@"description"];


    cell.selectionStyle = UITableViewCellSelectionStyleNone;

    PFFile *listThumbnail = [object objectForKey:@"header"];
    cell.listViewImage.image = [UIImage imageNamed:@"loading_image_stream.png"]; // placeholder image
    cell.listViewImage.file = listThumbnail;
    [cell.listViewImage loadInBackground:NULL];

    return cell;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForNextPageAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [super tableView:tableView cellForNextPageAtIndexPath:indexPath];
    cell.textLabel.font = [cell.textLabel.font fontWithSize:kPAWWallPostTableViewFontSize];
    return cell;
}

If I have all the content of the //configure cell in the cell == nil the it's fast but it show up 3 of the 9 unique datarows and repeat those 3 unique content cell 3 times?

Edit extra code within ExploreStreamCustomCell.m

#import "ExploreStreamCustomCell.h"

@implementation ExploreStreamCustomCell

@synthesize listViewImage, 
iconLocation, 
iconPeople, 
iconCheckins, 
listItemTitle, 
locationLabel, 
peopleLabel, 
checkinsLabel, 
descriptionLabel,
listItemView;


- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
    if(self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]){
        //Initialization code
        listItemView = [[UIView alloc] init];
        listViewImage = [[PFImageView alloc] init];
        iconLocation = [[UIImageView alloc] init];
        iconPeople = [[UIImageView alloc] init];
        iconCheckins = [[UIImageView alloc] init];
        listItemTitle = [[UILabel alloc] init];     
        locationLabel = [[UILabel alloc] init]; 
        peopleLabel = [[UILabel alloc] init];
        checkinsLabel = [[UILabel alloc] init]; 
        descriptionLabel = [[UILabel alloc] init];

        listViewImage.image = [UIImage imageNamed:@"nachtwacht_list_formaat.png"];
        iconLocation.image = [UIImage imageNamed:@"icon_magenta_location.png"];
        iconPeople.image = [UIImage imageNamed:@"icon_magenta_people.png"];
        iconCheckins.image = [UIImage imageNamed:@"icon_magenta_checkins.png"];
        listItemTitle.text = @"text";
        locationLabel.text = @"0,7 km";
        peopleLabel.text = @"34";
        checkinsLabel.text = @"61";
        descriptionLabel.text = @"Description text.";

        [self.contentView addSubview:listItemView];
        [self.contentView addSubview:listViewImage];
        [self.contentView addSubview:iconLocation];
        [self.contentView addSubview:iconPeople];
        [self.contentView addSubview:iconCheckins];
        [self.contentView addSubview:listItemTitle];
        [self.contentView addSubview:locationLabel];
        [self.contentView addSubview:peopleLabel];
        [self.contentView addSubview:checkinsLabel];
        [self.contentView addSubview:descriptionLabel];
    }
    return self;
}

- (void)layoutSubviews {
    [super layoutSubviews];
    CGRect contentRect = self.contentView.bounds;
    CGFloat boundsX = contentRect.origin.x;
    CGRect frame;

    frame= CGRectMake(boundsX+0 , 33, 280, 124);
    listViewImage.frame = frame;
    listViewImage.contentMode = UIViewContentModeScaleAspectFill;
    listViewImage.layer.masksToBounds = YES;

    //listViewImage.backgroundColor = [UIColor lightGrayColor];

    frame= CGRectMake(boundsX+20 , 164, 12, 18);
    iconLocation.frame = frame;
    //iconLocation.backgroundColor = [UIColor lightGrayColor];

    frame= CGRectMake(boundsX+102 , 164, 24, 18);
    iconPeople.frame = frame;
    //iconPeople.backgroundColor = [UIColor lightGrayColor];

    frame= CGRectMake(boundsX+193 , 164, 20, 16);
    iconCheckins.frame = frame;
    //iconLocation.backgroundColor = [UIColor lightGrayColor];

    frame= CGRectMake(boundsX+0 , 0, 280, 33);
    listItemView.frame = frame;
    listItemView.backgroundColor = [UIColor colorWithRed:0.749 green:0.000 blue:0.243 alpha:1.000];


    frame= CGRectMake(boundsX+20 , 3, 240, 29);
    listItemTitle.frame = frame;
    //listItemTitle.textColor = [UIColor colorWithRed:250.0f/255.0f green:194.0f/255.0f blue:9.0f/255.0f alpha:0.8f];
    listItemTitle.textAlignment = UITextAlignmentLeft;
    listItemTitle.font = [UIFont boldSystemFontOfSize:15];
    listItemTitle.textColor = [UIColor whiteColor];
    listItemTitle.backgroundColor = [UIColor clearColor];
    listItemTitle.lineBreakMode = UILineBreakModeTailTruncation;
    //listItemTitle.backgroundColor = [UIColor orangeColor];

    frame= CGRectMake(boundsX+40 , 164, 57, 21);
    locationLabel.frame = frame;
    locationLabel.textAlignment = UITextAlignmentLeft;
    locationLabel.font = [UIFont boldSystemFontOfSize:12];
    locationLabel.textColor = [UIColor colorWithRed:0.749 green:0.000 blue:0.243 alpha:1.000];
    locationLabel.backgroundColor = [UIColor clearColor];
    locationLabel.lineBreakMode = UILineBreakModeTailTruncation;
    locationLabel.numberOfLines = 1;
    //locationLabel.backgroundColor = [UIColor redColor];

    frame= CGRectMake(boundsX+134 , 164, 57, 21);
    peopleLabel.frame = frame;
    peopleLabel.textAlignment = UITextAlignmentLeft;
    peopleLabel.font = [UIFont boldSystemFontOfSize:12];
    peopleLabel.textColor = [UIColor colorWithRed:0.749 green:0.000 blue:0.243 alpha:1.000]; 
    peopleLabel.backgroundColor = [UIColor clearColor];
    peopleLabel.lineBreakMode = UILineBreakModeTailTruncation;
    peopleLabel.numberOfLines = 1;

    frame= CGRectMake(boundsX+221 , 164, 51, 21);
    checkinsLabel.frame = frame;
    checkinsLabel.textAlignment = UITextAlignmentLeft;
    checkinsLabel.font = [UIFont boldSystemFontOfSize:12];
    checkinsLabel.textColor = [UIColor colorWithRed:0.749 green:0.000 blue:0.243 alpha:1.000]; 
    checkinsLabel.backgroundColor = [UIColor clearColor];
    checkinsLabel.lineBreakMode = UILineBreakModeTailTruncation;
    checkinsLabel.numberOfLines = 1;

    frame= CGRectMake(boundsX+0 , 189, 280, 55);
    descriptionLabel.frame = frame;
    descriptionLabel.textAlignment = UITextAlignmentLeft;
    descriptionLabel.font = [UIFont systemFontOfSize:13];
    descriptionLabel.backgroundColor = [UIColor clearColor];
    descriptionLabel.lineBreakMode = UILineBreakModeTailTruncation;
    descriptionLabel.numberOfLines = 3;
}

- (void)setSelected:(BOOL)selected animated:(BOOL)animated {

    [super setSelected:selected animated:animated];

    // Configure the view for the selected state
}


/*
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}


// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

@end

Answer 1

A great way to explore the inefficiencies of your code is to use Instruments' Time Profiler tool. The Time Profiler will let you see how much time is being spent on each task, line-by-line in your code.

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I would recommend the following settings for profiling:

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From Apple's Face Detection sample app:

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You can then double click any line (higher percentages mean more time is being devoted to that method call) to see in the code how much time is spent in each place.

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From here you can begin to figure out where you are being inefficient and see exactly what is taking up so much time. Good luck!