UISheetPresentationController

ViewController.swift

//
//  ViewController.swift
//  Sheets
//
//  Created by Kyle Bashour on 6/7/21.
//

import UIKit

class ViewController: UIViewController, UISheetPresentationControllerDelegate {

    var sheetPresentationController: UISheetPresentationController {
        presentationController as! UISheetPresentationController
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .systemBackground

        let presentButton = makeButton(title: "Present Sheet") {
            let viewController = ViewController()
            self.present(viewController, animated: true)
        }

        let grabberButton = makeButton(title: "Toggle Grabber") {
            self.sheetPresentationController.animateChanges {
                self.sheetPresentationController.prefersGrabberVisible.toggle()
            }
        }

        let detentButton = makeButton(title: "Toggle Detent") {
            self.sheetPresentationController.animateChanges {
                if self.sheetPresentationController.selectedDetentIdentifier == .medium {
                    self.sheetPresentationController.selectedDetentIdentifier = .large
                } else {
                    self.sheetPresentationController.selectedDetentIdentifier = .medium
                }
            }
        }

        let cornerRadiusLabel = UILabel()
        cornerRadiusLabel.text = "Corner Radius"

        let cornerRadiusSlider = UISlider(frame: .zero, primaryAction: .init { action in
            let slider = action.sender as! UISlider
            let value = slider.value

            self.sheetPresentationController.animateChanges {
                // Not public (yet?)
                self.sheetPresentationController.setValue(CGFloat(value), forKey: "preferredCornerRadius")
            }
        })

        cornerRadiusSlider.minimumValue = 0
        cornerRadiusSlider.maximumValue = 100

        let stack = UIStackView(arrangedSubviews: [
            presentButton,
            grabberButton,
            detentButton,
            cornerRadiusLabel,
            cornerRadiusSlider,
            UIView()
        ])

        stack.spacing = 20
        stack.axis = .vertical
        stack.translatesAutoresizingMaskIntoConstraints = false
        stack.alignment = .center
        stack.distribution = .fill

        view.addSubview(stack)
        NSLayoutConstraint.activate([
            stack.topAnchor.constraint(equalTo: view.layoutMarginsGuide.topAnchor, constant: 80),
            stack.bottomAnchor.constraint(equalTo: view.layoutMarginsGuide.bottomAnchor),
            stack.leadingAnchor.constraint(equalTo: view.layoutMarginsGuide.leadingAnchor),
            stack.trailingAnchor.constraint(equalTo: view.layoutMarginsGuide.trailingAnchor),

            cornerRadiusSlider.widthAnchor.constraint(equalTo: stack.widthAnchor),
        ])

        sheetPresentationController.delegate = self
        sheetPresentationController.selectedDetentIdentifier = .large
        sheetPresentationController.prefersGrabberVisible = true
        sheetPresentationController.detents = [
            .medium(),
            .large(),
        ]
    }

    private func makeButton(title: String, handler: @escaping () -> Void) -> UIButton {
        let button = UIButton(configuration: .tinted(), primaryAction: .init { _ in
            handler()
        })

        button.setTitle(title, for: .normal)
        return button
    }

    func sheetPresentationControllerDidChangeSelectedDetentIdentifier(_ sheetPresentationController: UISheetPresentationController) {
        // Doesn't seem to work
        print("Detent changed")
    }
}