Swift iOS Set scrollView constraint below navigati

问题:

So my UIViewController is embedded in a navigation controller. I programatically add the navigation buttons and now trying to add a scrollView below this navigation bar. The problem I'm having is this is filling the full frame size and going under the navigation bar.

How do I programatically set constraints of this scrollview?

var scrollView: UIScrollView!
var containerView = UIView()

override func viewDidLoad() {
    super.viewDidLoad()
    self.navigationItem.title = "Filters"
    // add some buttons on the navigation

    self.scrollView = UIScrollView()
    self.scrollView.backgroundColor = UIColor.grayColor()
    self.scrollView.contentSize = CGSizeMake(self.view.frame.size.width, self.view.frame.size.height)

    containerView = UIView()

    scrollView.addSubview(containerView)
    view.addSubview(scrollView)

    let label = UILabel(frame: CGRectMake(0, 0, 100, 21))
    label.text = "my label"
    containerView.addSubview(label)
}

回答1:

While Clafou's answer is certainly correct, if you don't need transparency and want to start under navigation bar, the really proper way is to change behavior of the ViewController so it fits the content properly. To do that, you have two options:

1) Assuming you have Storyboard, go to ViewController Attributes Inspector and disable "Under top bars"

2) Assuming you are everything through code, you will want to look for following properties - edgesForExtendedLayout, and extendedLayoutIncludesOpaqueBars. There is great answer for that already on SO so I won't cover it here.

Hope it helps!

回答2:

The only way I managed to get this working on iOS11 was like this

if (@available(iOS 11.0, *)) {
    scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
} else {
    // Fallback on earlier versions
}

回答3:

While using auto-layout, just make sure that you give the top-constraint of UIScrollView with Top Layout Guide, not with superview of scroll view.

回答4:

Use the contentInset property of your UIScrollView. For example if you want a gap of 44 points at the top:

self.scrollView.contentInset = UIEdgeInsets(top: 44, left: 0, bottom: 0, right: 0)

回答5:

In Objective-C I usually set the 'edgesForExtendedLayout' Property to UIRectEdgeNone:

if ([self respondsToSelector:@selector(edgesForExtendedLayout)])
    self.edgesForExtendedLayout = UIRectEdgeNone;

Nevertheless I would recommend to bind the Constraints to the topLayoutGuide

func addScrollViewConstraints() {
    var scrollViewContraints = [NSLayoutConstraint]()
    scrollViewContraints.append(NSLayoutConstraint(item: scrollView,
        attribute: NSLayoutAttribute.Top,
        relatedBy: NSLayoutRelation.Equal,
        toItem: self.topLayoutGuide,
        attribute:NSLayoutAttribute.Bottom,
        multiplier: 1.0,
        constant: 0.0))
    scrollViewContraints.append(NSLayoutConstraint(item: scrollView,
        attribute: NSLayoutAttribute.Bottom,
        relatedBy: NSLayoutRelation.Equal,
        toItem: self.bottomLayoutGuide,
        attribute:NSLayoutAttribute.Top,
        multiplier: 1.0,
        constant: 0.0))
    scrollViewContraints.append(NSLayoutConstraint(item: scrollView,
        attribute: NSLayoutAttribute.Leading,
        relatedBy: NSLayoutRelation.Equal,
        toItem: self.view,
        attribute:NSLayoutAttribute.Leading,
        multiplier: 1.0,
        constant: 0.0))
    scrollViewContraints.append(NSLayoutConstraint(item: scrollView,
        attribute: NSLayoutAttribute.Trailing,
        relatedBy: NSLayoutRelation.Equal,
        toItem: self.view,
        attribute:NSLayoutAttribute.Trailing,
        multiplier: 1.0,
        constant: 0.0))
    self.view.addConstraints(scrollViewContraints)
}

Hope this works for you.