一、需知
iOS13更新后擅腰，通過 present 方式呈現(xiàn)出來的畫面，默認呈現(xiàn)樣式變更為UIModalPresentationStyle.automatic翁潘，表現(xiàn)為浮動效果趁冈，且可以通過下拉手勢將畫面dismiss。
需求一：希望iOS13以上present的畫面樣式跟以前一樣顯示為全屏效果
實現(xiàn)方式拜马，設置modalPresentationStyle為fullScreen渗勘。
1.在創(chuàng)建實例時設置，代碼如下：
let vc = ViewController()
vc.modalPresentationStyle = .fullScreen
present(vc, animated: true, completion: nil)
2.或者在初始化方法中設置俩莽，代碼如下：
// 適用于純代碼構建的UIViewController
override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
modalPresentationStyle = .fullScreen
}
// 適用于xib或storyboard構建的UIViewController
required init?(coder: NSCoder) {
super.init(coder: coder)
modalPresentationStyle = .fullScreen
}
需求二：希望iOS13以上保留浮動效果旺坠，禁用下拉手勢dismiss畫面
實現(xiàn)方式：設置isModalInPresentation屬性為true。
代碼跟上面的實現(xiàn)方式一樣扮超。
需求三：監(jiān)測下拉手勢取刃，可以在用戶下拉時作出反應
此實現(xiàn)方式只適用于present的畫面放在UINavigationController里
實現(xiàn)方式：
1.設置代理
let vc = ViewController()
let navi = UINavigationController(rootViewController: vc)
navi.presentationController?.delegate = vc
present(vc, animated: true, completion: nil)
2.實現(xiàn)UIAdaptivePresentationControllerDelegate的代理方法func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController)，
此方法需同屬性isModalInPresentation結合使用出刷，當isModalInPresentation = true時璧疗，下拉試圖dismiss畫面時，才會調用此方法巷蚪。
override func viewWillLayoutSubviews() {
// Ensure textView.text is up to date
textView.text = editedText
// If our model has unsaved changes, prevent pull to dismiss and enable the save button
let hasChanges = self.hasChanges
isModalInPresentation = hasChanges
saveButton.isEnabled = hasChanges
}
...
func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController) {
// The user pulled down with unsaved changes
// Clarify the user's intent by asking whether they intended to cancel or save
print("isModalInPresentation=\(self.isModalInPresentation)")
confirmCancel(showingSave: true)
}
上面的代碼來自官方 Simple Code病毡，請自行下載：
https://developer.apple.com/documentation/uikit/view_controllers/disabling_pulling_down_a_sheet
