currentContext 表示样式改变子视图控制器视图的大小

Question

我有一个父视图控制器和一个子视图控制器，它们占据了父视图的一部分：

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let childVC = ChildVC()
        addChild(childVC)
        childVC.view.frame = CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: 200, height: 200))
        view.addSubview(childVC.view)
        childVC.didMove(toParent: self)
    }
}

class ChildVC: UIViewController {
    override func loadView() {
        let v = UIView()
        v.backgroundColor = .cyan
        view = v
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let button = UIButton(type: .system)
        button.setTitle("Present", for: .normal)
        button.addTarget(self, action: #selector(pressed), for: .touchUpInside)
        button.sizeToFit()
        view.addSubview(button)

    }
    
    @objc func pressed() {
        self.definesPresentationContext = true
        self.providesPresentationContextTransitionStyle = true
        self.modalTransitionStyle = .crossDissolve
        let pvc = PresentedVC()
        pvc.modalPresentationStyle = .currentContext
        self.present(pvc, animated: true, completion: nil)
    }
}

class PresentedVC: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .yellow
        
        let button = UIButton(type: .system)
        button.setTitle("Dismiss", for: .normal)
        button.addTarget(self, action: #selector(pressed), for: .touchUpInside)
        button.sizeToFit()
        view.addSubview(button)
    }
    
    @objc func pressed() {
        self.dismiss(animated: true, completion: nil)
    }
}

当我使用currentContext 样式呈现视图控制器时，它会呈现应有的新视图控制器，仅覆盖子视图控制器的视图：

但是，当我关闭它时，ChildVC 的主视图的大小会占据整个屏幕：

当我记录 ChildVC 的主视图的超级视图时，它仍然是父视图控制器主视图的子视图，所以我不确定为什么会这样。

Answer 1

只需将您的 presentationStyle 更改为 .overCurrentContext，如下所示：

    @objc func pressed() {
        self.definesPresentationContext = true
        self.providesPresentationContextTransitionStyle = true
        self.modalTransitionStyle = .crossDissolve
        let pvc = PresentedVC()
        pvc.modalPresentationStyle = .overCurrentContext // <-- here
        pvc.modalTransitionStyle = .crossDissolve        // <-- and here
        self.present(pvc, animated: true, completion: nil)
    }

它将防止不必要的升级。