Bottom Navigation Drawer doesn't show up (Swift) - ios

Question

I currently working on an iOS app and I want to use a bottom navigation drawer from material-io. So I did it like it is explained in the examples on the site. But when I present the navigation Drawer the ViewController only gets a bit darker and the contentView of the drawer isn't shown.
Here is my Code:
import Foundation
import UIKit
import MaterialComponents
class CreateSubjectView: UIViewController, UITextFieldDelegate {
...
override func viewDidLoad() {
...
let bottomDrawerViewController = MDCBottomDrawerViewController()
self.modalPresentationStyle = .popover
let newViewController = self.storyboard?.instantiateViewController(withIdentifier: "TEST")
bottomDrawerViewController.contentViewController = newViewController
present(bottomDrawerViewController, animated: true, completion: nil)
...
}
...
}

Answer 1

Your view controller to be shown in drawer must have specified preferred content size.
Here is a demo of minimal controller. (Note: modalPresentationStyle = .popover has no effect on MDCBottomDrawerViewController)
Tested with Xcode 12
// button action in parent controller
#objc private func presentNavigationDrawer() {
let bottomDrawerViewController = MDCBottomDrawerViewController()
bottomDrawerViewController.contentViewController = DemoViewController()
present(bottomDrawerViewController, animated: true, completion: nil)
}
}
class DemoViewController: UIViewController {
override func loadView() {
super.loadView()
let view = UIView()
view.backgroundColor = .red
self.view = view
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
// specify your content preferred height explicitly
self.preferredContentSize = CGSize(width: 0, height: 400) // required !!
}
#available(iOS 11.0, *)
override func viewSafeAreaInsetsDidChange() {
super.viewSafeAreaInsetsDidChange()
// specify your content preferred height explicitly
self.preferredContentSize = CGSize(width: 0, height: 400) // required !!
}
}

Answer 2

Move this to viewWillAppear/ viewDidAppear once as it's too early for viewDidLoad to present a vc
class CreateSubjectView: UIViewController, UITextFieldDelegate {
let bottomDrawerViewController = MDCBottomDrawerViewController()
var once = true
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if once {
let newViewController = self.storyboard?.instantiateViewController(withIdentifier: "TEST")
bottomDrawerViewController.contentViewController = newViewController
present(bottomDrawerViewController, animated: true, completion: nil)
once = false
}
}
}