Enlarge UIScrollview's content size dynamically when adding views programatically

Question

I have the following situation:

UIScrollView ("_scrollView") with one child: UIView
UIView ("_layoutContainer") has a unknown number of childViews
childViews of UIView are added programmatically and their constraints are set programmatically.

Code for adding childviews (and my try to resize scrollview's content size):

- (void)viewDidLoad {
    [super viewDidLoad];
    UIView* lastLabel = _topCollectionView;
    for (int i = 0; i<50; i++) {
        UILabel* imageLabelView = [UILabel new];
        imageLabelView.translatesAutoresizingMaskIntoConstraints = NO;

        [_layoutContainer addSubview:imageLabelView];

        [_layoutContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(10)-[labelview]-(10)-|" options:0 metrics:nil views:@{@"labelview":imageLabelView}]];
        [_layoutContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[previousLabel]-(10)-[imagelabel(40)]" options:0 metrics:nil views:@{@"previousLabel":lastLabel, @"imagelabel":imageLabelView}]];

        imageLabelView.text = @"DUMMY";
        lastLabel = imageLabelView;
    }

    [_layoutContainer setNeedsLayout];
    [_layoutContainer layoutIfNeeded];
    _scrollView.contentSize = _layoutContainer.frame.size;
    [_scrollView invalidateIntrinsicContentSize];
}

My Storyboard Constraints look like this:

This code works without any constraint errors in log and it looks like expected.

My problem is: The scrollview's content size doesn't change. I can add as many labels as I want to, but scrolling never works. Can you please help me to dynamically enlarge my scrollview?

Andrea · Accepted Answer · 2015-12-17 11:23:59Z

1

If all the constraints makes a sufficient set to define an intrinsic content size in the container view, the scroll view -contentSize should resize accordingly, just need to call -(void)invalidateIntrinsicContentSize on the scroll view after you added the content.

- (void)viewDidLoad {
    [super viewDidLoad];
    UIView* lastLabel = _topCollectionView;
    for (int i = 0; i<50; i++) {
        UILabel* imageLabelView = [UILabel new];
        imageLabelView.translatesAutoresizingMaskIntoConstraints = NO;

        [_layoutContainer addSubview:imageLabelView];

        [_layoutContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(10)-[labelview]-(10)-|" options:0 metrics:nil views:@{@"labelview":imageLabelView}]];
        [_layoutContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[previousLabel]-(10)-[imagelabel(40)]" options:0 metrics:nil views:@{@"previousLabel":lastLabel, @"imagelabel":imageLabelView}]];

        imageLabelView.text = @"DUMMY";
        lastLabel = imageLabelView;
    }

    [_layoutContainer setNeedsLayout];
    [_layoutContainer layoutIfNeeded];
    [_scrollView invalidateIntrinsicContentSize];
    [_scrollView setNeedsLayout];
    [_scrollView layoutIfNeeded];
}

edited Dec 17, 2015 at 11:23

answered Dec 17, 2015 at 11:10

Andrea

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4 Comments

Jörn Buitink Over a year ago

Doesn't work. If I log the _layoutContainer size after adding all the view, i still get {{0, 0}, {1024, 768}} . I think the View inside the scrollView isn't updated. Will test some more..

Andrea Over a year ago

Ok, try also that: do not call -layoutIfNeeded in the loop, after the loop say to the container view -setNeedsLayout and then -layoutIfNeeded. You should alway mark a view as in need of layout or the layout engine will skip it. I Updated the answer

Jörn Buitink Over a year ago

Did it (and updated the code in my question). Unfortunately it did not change anything.

Jörn Buitink Over a year ago

Got it! I had to add a bottom view constraint for the last label (after the loop):

if (lastLabel) {         [_layoutContainer addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[previousLabel]-(10)-|" options:0 metrics:nil views:@{@"previousLabel":lastLabel}]];              }

. Please edit your answer so I can accept it. Your if all the constraints makes a sufficient set (...) pointed me in the right direction

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