specktro specktro - 5 months ago 173
iOS Question

Dynamic UILabel height inside UIScrollView with Autolayout

I am using autolayout with

UIScrollView
to show some attributes from an object. I download this information dinamically from web service. The scrollview has a constant width (because I don't want to have a vertical scroll behavior) and its subviews respect this width with a group of constraints, but I can't to increase the
UILabel
's height dynamically.

I code everything and I use
viewDidLoad
selector to create subviews...

- (void)viewDidLoad {
[super viewDidLoad];
.
.
.

UILabel *descriptionLabel = [[UILabel alloc] initWithFrame:CGRectZero];
descriptionLabel.translatesAutoresizingMaskIntoConstraints = NO;
descriptionLabel.numberOfLines = 0;
descriptionLabel.lineBreakMode = NSLineBreakByWordWrapping;
descriptionLabel.opaque = YES;
descriptionLabel.backgroundColor = [UIColor clearColor];
descriptionLabel.textColor = [UIColor whiteColor];
descriptionLabel.textAlignment = NSTextAlignmentRight;
descriptionLabel.font = [UIFont appetitoMediumItalicFontWithSize:15.0f];
descriptionLabel.text = NSLocalizedStringFromTable(@"APT_DISH_DETAIL_DESCRIPTION", @"DishDetail", @"Etiqueta que contiene la descripciĆ³n del platillo");
[descriptionLabel setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[self.detailContentScrollView addSubview:descriptionLabel];
self.descriptionLabelS = descriptionLabel;

.
.
.
}


You can watch the
self.detailContentScrollView
variable, this is an
IBOulet
created from view controller's nib.

Then I use the
updateConstraints
selector...

- (void)updateConstraints {
[super updateConstraints];
// This dictionary has more variables, ok
NSDictionary *viewsDict = @{@"dish_description_label": self.descriptionLabelS};
.
.
.

[self.descriptionLabelS setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[self.detailContentScrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[view1][dish_description_label]-[view2][view3][view4]-|" options:0 metrics:nil views:viewsDict]];

.
.
.
}


and finally, when I receive the web service's info, I send
sizeToFit
's
UILabel
selector and
layoutIfNeeded
from the scrollview. But my
UILabel
never resizes itself with the new content. What am I doing wrong?

Answer

UIScrollView content size is updated dynamically with autolayout, maybe you only must do the following

- (void) setupScroll
{
    [_scrollView setTranslatesAutoresizingMaskIntoConstraints:NO];
    [_contentView setTranslatesAutoresizingMaskIntoConstraints:NO];

    [_scrollView addSubview:_contentView];

    NSArray *horizontal = [NSLayoutConstraint constraintsWithVisualFormat:@"|[_contentView]|"
                                                                  options:0
                                                                  metrics:nil
                                                                    views:NSDictionaryOfVariableBindings(_contentView)];
    NSArray *vertical = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[_contentView]|"
                                                                options:0
                                                                metrics:nil
                                                                  views:NSDictionaryOfVariableBindings(_contentView)];

    [_scrollView addConstraints:horizontal];
    [_scrollView addConstraints:vertical];

    UIView *mainView = self.view;
    horizontal = [NSLayoutConstraint constraintsWithVisualFormat:@"|[_contentView(==mainView)]|"
                                                         options:0
                                                         metrics:nil
                                                           views:NSDictionaryOfVariableBindings(_contentView, mainView)];

    [mainView addConstraints:horizontal];
}

Where _contentView is your UILabel (If you have a more complex view hierarchy put on a view container) and self.view is the controller view (or anything else). Hope this helps also: iOS Autolayout with UIScrollview: Why does content view of scroll view not fill the scroll view?....

Also don't forget to establish your UILabel preferredMaxLayoutWidth

Cheers!

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