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| import Foundation | |
| import UIKit | |
| // emulates table view sticky headers and demonstrates content inset usage | |
| public class FakeTableViewController: UIViewController, UIScrollViewDelegate { | |
| // set up views neatly using anonymous closures | |
| let scrollView: UIScrollView = { | |
| let v = UIScrollView() | |
| v.backgroundColor = UIColor.lightGray | |
| return v | |
| }() | |
| // this will be the header that gets 'scrolled over', kind of like a refresh control | |
| let headerView: UIView = { | |
| let v = UIView() | |
| v.backgroundColor = UIColor.blue.withAlphaComponent(0.5) | |
| v.translatesAutoresizingMaskIntoConstraints = false | |
| return v | |
| }() | |
| // this will be a sticky section header ala UITableView plain | |
| let sectionHeaderView: UIView = { | |
| let v = UIView() | |
| v.backgroundColor = UIColor.red.withAlphaComponent(0.5) | |
| v.translatesAutoresizingMaskIntoConstraints = false; | |
| return v | |
| }() | |
| // some content to take up the screen | |
| let fakeContentView: UIView = { | |
| let v = UIView() | |
| v.backgroundColor = UIColor.white | |
| v.translatesAutoresizingMaskIntoConstraints = false; | |
| return v | |
| }() | |
| // the constraints we need to modify later | |
| var headerTopConstraint: NSLayoutConstraint! | |
| var contentWidthConstraint: NSLayoutConstraint! | |
| // we don't want no nibs | |
| public override func loadView() { | |
| // these lines happen automatically in UITableViewController/UICollectionViewController subclasses | |
| self.scrollView.delegate = self; | |
| self.scrollView.alwaysBounceVertical = true | |
| // cause it's a fake table | |
| self.scrollView.isDirectionalLockEnabled = true | |
| // add views and fix to edges | |
| // order matters for layering | |
| [self.headerView, self.fakeContentView, self.sectionHeaderView].forEach { | |
| self.scrollView.addSubview($0) | |
| $0.leftAnchor.constraint(equalTo: self.scrollView.leftAnchor).isActive = true | |
| $0.rightAnchor.constraint(equalTo: self.scrollView.rightAnchor).isActive = true | |
| } | |
| // fixed constraints - heights | |
| self.headerView.heightAnchor.constraint(equalToConstant: 50).isActive = true | |
| self.sectionHeaderView.heightAnchor.constraint(equalToConstant: 20).isActive = true | |
| self.fakeContentView.heightAnchor.constraint(equalToConstant: 1000).isActive = true | |
| // fix content to top and bottom | |
| self.fakeContentView.topAnchor.constraint(equalTo: self.scrollView.topAnchor).isActive = true | |
| self.fakeContentView.bottomAnchor.constraint(equalTo: self.scrollView.bottomAnchor).isActive = true | |
| // keep the section bottom fixed to the top of the content *if it can* be | |
| do { | |
| let c = self.sectionHeaderView.bottomAnchor.constraint(equalTo: self.fakeContentView.topAnchor) | |
| c.priority = UILayoutPriorityDefaultLow | |
| c.isActive = true | |
| } | |
| // require that it's no higher than the top of the background header (which is the top of the content window) | |
| self.sectionHeaderView.topAnchor.constraint(greaterThanOrEqualTo: self.headerView.topAnchor).isActive = true | |
| // edge insets | |
| self.scrollView.contentInset = UIEdgeInsets(top: 70, left: 0, bottom: 0, right: 0) | |
| self.scrollView.scrollIndicatorInsets = UIEdgeInsets(top: 70, left: 0, bottom: 0, right: 0) | |
| // mutable constraints | |
| // make sure width of content exists, otherwise size = 0,0 - table views do not have this problem | |
| self.contentWidthConstraint = { | |
| let c = self.headerView.widthAnchor.constraint(equalToConstant: 0) | |
| c.isActive = true | |
| return c | |
| }() | |
| // keep the 'behind' header fixed | |
| self.headerTopConstraint = { | |
| let c = self.headerView.topAnchor.constraint(equalTo: self.scrollView.topAnchor) | |
| c.isActive = true | |
| return c | |
| }() | |
| // always set self.view last and don't use it until then | |
| self.view = self.scrollView | |
| } | |
| public override func viewWillLayoutSubviews() { | |
| super.viewWillLayoutSubviews() | |
| // this forces the scrolling content to fill the space (width) given to the view controller | |
| self.contentWidthConstraint.constant = self.view.frame.width | |
| // TODO: take into account the edge insets of the VC w/r/t status bar and UINavigationBar | |
| } | |
| public func scrollViewDidScroll(_ scrollView: UIScrollView) { | |
| self.headerTopConstraint.constant = scrollView.contentOffset.y | |
| // adjust scroll indicator offsets here to match content bouncing | |
| } | |
| } |
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