UIScrollView contentSize not working

Question

I put a UIScrollView in my nib's view, and linked it to a an IBOutlet property.

Now, when I do this in my viewDidLoad method, it seems to have no effect on the contentSize:

self.sv.backgroundColor = [UIColor yellowColor]; // this works
CGSize size =  CGSizeMake(1000.0, 1000.0); 
[self.sv setContentSize:size]; // this does not

It behaves as if the contentSize was the same as the frame. What's going on? This started working when I turned off AutoLayout. Why?

Answer 1

I had the same problem. Auto Layout for UIScrollView is messed up.

Work around: Put everything in the UIScrollView into another UIView, and put that UIView as the only child of the UIScrollView. Then you can use Auto Layout.

If things near the end is messed up (the end of whichever direction your UIScrollView scrolls), change the constraint at the end to have the lowest possible priority.

Answer 2

I tried viewWillLayoutSubviews to update scrollView's contentSize, it worked for me.

- (void)viewDidLayoutSubviews
{
  [self.bgScrollView setContentSize:CGSizeMake(320, self.view.frame.size.height* 1.5)];
}

Apple Doc

-(void)viewDidLayoutSubviews

Called to notify the view controller that its view has just laid out its subviews.

Discussion

When the bounds change for a view controller’s view, the view adjusts the positions of its subviews and then the system calls this method. However, this method being called does not indicate that the individual layouts of the view’s subviews have been adjusted. Each subview is responsible for adjusting its own layout.

Your view controller can override this method to make changes after the view lays out its subviews. The default implementation of this method does nothing.

Answer 3

I could never get auto layout based on constraints to work. Since my view was already a subclass UIScrollView I solved it by overriding setContentView: and ignoring auto layouts zero height setContentSize: message.

@interface MyView : UIScrollView {}
@end

@implementation MyView
- (void)setContentSize:(CGSize)aSize {
    if (aSize.height > 0)
        [super setContentSize:aSize];
}
@end

Answer 4

I got Autolayout to work for paginated scroll views whose pages occupy the full-width of the screen. The pages automatically resize according to the scroll view's size. I haven't tested this for lesser-width scroll views but do comment away if it works--I beleieve it should. Targeted for iOS 9, wrote code in Swift 2, used a mix of IB's and custom code in awakeFromNib.

Steps:

• Define a full-screen scroll view.
• Inside the scroll view, add a UIView (I called mine contentView) whose top, trailing, bottom, and leading edges to the scroll view are all zero; the height is equal to the scroll view's; but the width is the scroll view's width times the number of pages. If you're doing this visually, you will see your content view extend beyond your scroll view in Inteface Builder.
• For every "page" inside the contentView, add Autolayout rules to put them side-by-side each other, but most importantly, give them each a constraint so that their widths are equal to the scroll view's, not the content view's.

Sample code below. embedChildViewController is just my convenience method for adding child VCs--do look at setupLayoutRulesForPages. I have exactly two pages so the function is too simple, but you can expand it to your needs.

In my view controller:

override func loadView() {
    self.view = self.customView
}

override func viewDidLoad() {
super.viewDidLoad()

self.embedChildViewController(self.addExpenseVC, toView: self.customView.contentView, fillSuperview: false)
self.embedChildViewController(self.addCategoryVC, toView: self.customView.contentView, fillSuperview: false)
self.customView.setupLayoutRulesForPages(self.addExpenseVC.view, secondPage: self.addCategoryVC.view)
}

My custom view:

class __AMVCView: UIView {

    @IBOutlet weak var scrollView: UIScrollView!
    @IBOutlet weak var contentView: UIView!
    @IBOutlet weak var pageControl: UIPageControl!

    override func awakeFromNib() {
        super.awakeFromNib()

        self.scrollView.pagingEnabled = true
        self.scrollView.bounces = true
        self.scrollView.showsHorizontalScrollIndicator = false
        self.scrollView.showsVerticalScrollIndicator = false

        self.pageControl.numberOfPages = 2

        self.contentView.backgroundColor = UIColor.blueColor()
        self.scrollView.backgroundColor = UIColor.clearColor()
        self.backgroundColor = UIColor.blackColor()
    }

    func setupLayoutRulesForPages(firstPage: UIView, secondPage: UIView) {
        guard self.contentView.subviews.contains(firstPage) && self.contentView.subviews.contains(secondPage)
            else {
                return
        }

        let rules = [
            "H:|-0-[firstPage]-0-[secondPage]-0-|",
            "V:|-0-[firstPage]-0-|",
            "V:|-0-[secondPage]-0-|"
        ]
        let views = [
            "firstPage" : firstPage,
            "secondPage" : secondPage
        ]
        let constraints = NSLayoutConstraint.constraintsWithVisualFormatArray(rules, metrics: nil, views: views)

        UIView.disableAutoresizingMasksInViews(firstPage, secondPage)
        self.addConstraints(constraints)

        // Add the width Autolayout rules to the pages.
        let widthConstraint = NSLayoutConstraint(item: firstPage, attribute: .Width, relatedBy: .Equal, toItem: self.scrollView, attribute: .Width, multiplier: 1, constant: 0)
        self.addConstraint(widthConstraint)
    }

}

Answer 5

If you are using AutoLayout a really easy way to set the contentSize of a UIScrollView is just to add something like this:

CGFloat contentWidth = YOUR_CONTENT_WIDTH;

NSLayoutConstraint *constraintWidth = 
 [NSLayoutConstraint constraintWithItem:self.scrollView 
                              attribute:NSLayoutAttributeTrailing 
                              relatedBy:NSLayoutRelationEqual 
                                 toItem:self.scrollView 
                              attribute:NSLayoutAttributeLeading 
                             multiplier:1 
                               constant:contentWidth];

[self.scrollView addConstraint:constraintWidth];

Answer 6

A SUPER easy way to use AutoLayout with UIScrollViews inside Interface Builder:

Step 1: Create a UIScrollView

Step 2: Create a UIView that is a child of your scroll view like so:

-UIScrollView
---UIView
-----Your other content

(We'll call this one contentView).

Step 3: In the size inspector, give this view a height and width (say, 320x700).

Step 4 (using AutoLayout): Create unambiguous constraints from your contentView to its superview (the UIScrollView): connect the 4 edges (top, leading, trailing, bottom), then give it a defined width and height that you want it to scroll too.

For example: If your scroll view spans the entire screen, you could give your content view a width of [device width] and a height of 600; it will then set the content size of the UIScrollView to match.

OR:

Step 4 (not using AutoLayout): Connect both of these new controls to your view controller using IB (ctrl+drag from each control to your view controller's .h @implementation). Let's assume each is called scrollView and contentView, respectively. It should look like this:

@interface YourViewController : UIViewController

@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@property (strong, nonatomic) IBOutlet UIView *contentView;

@end

Step 5 (not using AutoLayout): In the view controller's .h file add (actually, override) the following method:

-(void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];
    self.scrollView.contentSize = self.contentView.frame.size;
}