How to create a custom UITableViewCell programmatically using AutoLayout
I'm trying to implement a UITableView that will behave similarly to the timeline of a twitter client. Right now I'm simply attempting to get two labels inside a UITableViewCell. As recommended by this Stack Overflow answer, I'm using a different reuseIdentifier for each layouts. My layouts are simple, consisting of either a single label or two labels. Eventually I will be adjusting the height of the UITableViewCells but first I need to get the cells populated with content.
I can get the labels so show up if I set their frame with initWithFrame:, however the constraints aren't being implemented.
Question: What is preventing the labels and constraints from appearing? I'm clearly missing something in my implementation of the UITableViewCell but I have no idea what it is.
Secondary question: Am I registering the UITableViewCell class correctly for each reuseIdentifier in
viewDidLoad?
This might come across as being difficult but Interface Builder confuses me, I would like to accomplish this all in code.
Here is the code for the custom UITableViewCell named TVTCell.h:
static NSString * const kCellIDTitle = @"CellWithTitle";
static NSString * const kCellIDTitleMain = @"CellWithTitleMain";
@interface TVTCell : UITableViewCell
{
NSString *reuseID;
}
@property (nonatomic, strong) UILabel *nameLabel;
@property (nonatomic, strong) UILabel *mainLabel;
@end
And TVTCell.m:
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
reuseID = reuseIdentifier;
nameLabel = [[UILabel alloc] init];
[nameLabel setTextColor:[UIColor blackColor]];
[nameLabel setBackgroundColor:[UIColor colorWithHue:32 saturation:100 brightness:63 alpha:1]];
[nameLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18.0f]];
[nameLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.contentView addSubview:nameLabel];
mainLabel = [[UILabel alloc] init];
[mainLabel setTextColor:[UIColor blackColor]];
[mainLabel setBackgroundColor:[UIColor colorWithHue:66 saturation:100 brightness:63 alpha:1]];
[mainLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18.0f]];
[mainLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.contentView addSubview:mainLabel];
[self.contentView setTranslatesAutoresizingMaskIntoConstraints:NO];
}
return self;
}
- (void)updateConstraints
{
[super updateConstraints];
NSDictionary *views = NSDictionaryOfVariableBindings(nameLabel, mainLabel);
if (reuseID == kCellIDTitle) {
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[nameLabel]|"
options: NSLayoutFormatAlignAllCenterX
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[nameLabel]|"
options: NSLayoutFormatAlignAllCenterX
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
}
if (reuseID == kCellIDTitleMain) {
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[nameLabel]|"
options: NSLayoutFormatAlignAllCenterX
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[mainLabel]|"
options: NSLayoutFormatAlignAllCenterX
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[nameLabel][mainLabel]|"
options: NSLayoutFormatAlignAllLeft
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
[self.contentView addConstraint:[NSLayoutConstraint constraintWithItem:nameLabel
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:0.0
constant:44.0]];
[self.contentView addConstraint:[NSLayoutConstraint constraintWithItem:nameLabel
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.contentView
attribute:NSLayoutAttributeNotAnAttribute
multiplier:0.0
constant:1]];
}
}
Sorry, ton of code. Here's my UITableView's tableView:cellForRowAtIndexPath:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.row == 0 || indexPath.row == 2 || indexPath.row == 3) {
TVTCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellIDTitle forIndexPath:indexPath];
[[cell nameLabel] setText:[nameArray objectAtIndex:indexPath.row]];
return cell;
} else if (indexPath.row == 1 || indexPath.row == 4 || indexPath.row == 5) {
TVTCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellIDTitleMain forIndexPath:indexPath];
[[cell nameLabel] setText:[nameArray objectAtIndex:indexPath.row]];
[[cell mainLabel] setText:[dataArray objectAtIndex:indexPath.row]];
return cell;
} else
{
UITableViewCell *badCell = [[UITableViewCell alloc] init];
NSLog(@"Warning! returning a cell that shouldnt be here");
badCell.textLabel.text = @"Warning!";
return badCell;
}
}
And lastly, the UITableView's viewDidLoad method:
- (void)viewDidLoad
{
[super viewDidLoad];
[[self tableView] registerClass:[TVTCell class] forCellReuseIdentifier:kCellIDTitle];
[[self tableView] registerClass:[TVTCell class] forCellReuseIdentifier:kCellIDTitleMain];
}
Answer
There are several things wrong with your code. First, I think you'll find, if you do some logging, that updateConstraints is never called. I would put all the code in the init method. Also, there are several things wrong in your constraints. The constraint where you set the height to 44 is not needed since you already have the labels pinned to the to and bottom of the cell. I don't know what you're trying to do with that last one, it looks like that would make the nameLabel 1 point wide. Also, you shouldn't set the translatesAutoresizingMaskIntoConstraints to NO for the content view, that causes weird effects. So this is the code I think you want:
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
reuseID = reuseIdentifier;
nameLabel = [[UILabel alloc] init];
[nameLabel setTextColor:[UIColor blackColor]];
[nameLabel setBackgroundColor:[UIColor colorWithHue:32 saturation:100 brightness:63 alpha:1]];
[nameLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18.0f]];
[nameLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.contentView addSubview:nameLabel];
mainLabel = [[UILabel alloc] init];
[mainLabel setTextColor:[UIColor blackColor]];
[mainLabel setBackgroundColor:[UIColor colorWithHue:66 saturation:100 brightness:63 alpha:1]];
[mainLabel setFont:[UIFont fontWithName:@"HelveticaNeue" size:18.0f]];
[mainLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.contentView addSubview:mainLabel];
NSDictionary *views = NSDictionaryOfVariableBindings(nameLabel, mainLabel);
if (reuseID == kCellIDTitle) {
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[nameLabel]|"
options: 0
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[nameLabel]|"
options: 0
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
}
if (reuseID == kCellIDTitleMain) {
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[nameLabel]|"
options:0
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[mainLabel]|"
options: 0
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[nameLabel][mainLabel(==nameLabel)]|"
options: 0
metrics:nil
views:views];
[self.contentView addConstraints:constraints];
}
}
return self;
}