ios - 试图模仿 Mail.app 撰写动画，使图层保持在 View 中

Question

我已经尝试了一段时间，但我不知道如何创建在 iOS 10+ 中看到的撰写动画，当您可以将新撰写的电子邮件向下拖动时，它会停留在底部并且应用程序的其余部分通常可以访问，然后当您点击它时，它会重新显示。

我创建了一个示例项目，其中我有一个 UIViewController，它显示另一个 UIViewController，它在 UINavigationController 中有一个 UIPanGestureRecognizer 触发 pangesture 状态分析器。

我确实可以拖动以关闭它，但我找不到保持框架的方法。

下面是我正在尝试完成的打印屏幕，然后是我使用的代码到我卡住的地方。

UIViewController 即 presentingViewController 类

//
//  ViewController.swift
//  dismissLayerTest
//
//  Created by Ivan Cantarino on 27/09/17.
//  Copyright © 2017 Ivan Cantarino. All rights reserved.
//

import UIKit

class ViewController: UIViewController, UIViewControllerTransitioningDelegate {


    @objc let interactor = Interactor()

    lazy var presentButton: UIButton = {
        let b = UIButton(type: .custom)
        b.setTitle("Present", for: .normal)
        b.setTitleColor(.black, for: .normal)
        b.addTarget(self, action: #selector(didTapPresentButton), for: .touchUpInside)
        return b
    }()

    lazy var testbutton: UIButton = {
        let b = UIButton(type: .custom)
        b.setTitle("test", for: .normal)
        b.setTitleColor(.black, for: .normal)
        b.addTarget(self, action: #selector(test), for: .touchUpInside)
        return b
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        view.backgroundColor = .white
        view.addSubview(presentButton)
        presentButton.anchor(top: nil, left: nil, bottom: nil, right: nil, paddingTop: 0, paddinfLeft: 0, paddingBottom: 0, paddingRight: 0, width: 100, height: 100)
        presentButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        presentButton.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        view.addSubview(testbutton)
        testbutton.anchor(top: nil, left: nil, bottom: presentButton.topAnchor, right: nil, paddingTop: 0, paddinfLeft: 0, paddingBottom: 100, paddingRight: 0, width: 100, height: 100)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @objc func didTapPresentButton() {
        let presentedVC = PresentedViewController()
        let navController = UINavigationController(rootViewController: presentedVC)

        navController.transitioningDelegate = self
        presentedVC.interactor = interactor // new
        navController.modalPresentationStyle = .custom
        navController.view.layer.masksToBounds = true

        present(navController, animated: true, completion: nil)

    }

    @objc func test() {
        print("test")
    }

    // Handles the presenting animation
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return CustomAnimationForPresentor()
    }


    // Handles the dismissing animation
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return CustomAnimationForDismisser()
    }


    // interaction controller, only for dismissing the view;
    func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        return interactor.hasStarted ? interactor : nil
    }

    // delegate do custom modal presentation style
    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
            return CustomPresentationController(presentedViewController: presented, presenting: presenting)
        }

}

UIViewController 2 即 presentedViewController

import Foundation
import UIKit


class PresentedViewController: UIViewController, UIViewControllerTransitioningDelegate, UIGestureRecognizerDelegate {



    @objc var interactor: Interactor? = nil
    @objc var panGr = UIPanGestureRecognizer()
    @objc var panTapRecon = UITapGestureRecognizer()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .green

        let leftB = UIBarButtonItem(barButtonSystemItem: .cancel, target: self, action: #selector(didTapCancel))
        navigationItem.leftBarButtonItem = leftB

        panGr = UIPanGestureRecognizer(target: self, action: #selector(handleGesture))
        navigationController?.navigationBar.addGestureRecognizer(panGr)

        panTapRecon = UITapGestureRecognizer(target: self, action: #selector(handleNavControllerTapGR))
        navigationController?.navigationBar.addGestureRecognizer(panTapRecon)
    }

    @objc func didTapCancel() {
        guard let interactor = interactor else { return }
        interactorFinish(interactor: interactor)
        dismiss(animated: true, completion: nil)
    }

    @objc func handleNavControllerTapGR(_ sender: UITapGestureRecognizer) {
        print("tap detected")
    }


    // Swipe gesture recognizer handler
    @objc func handleGesture(_ sender: UIPanGestureRecognizer) {

        //percentThreshold: This variable sets how far down the user has to drag
        //in order to trigger the modal dismissal. In this case, it’s set to 40%.
        let percentThreshold:CGFloat = 0.30

        // convert y-position to downward pull progress (percentage)
        let translation = sender.translation(in: view)
        let verticalMovement = translation.y / view.bounds.height
        let downwardMovement = fmaxf(Float(verticalMovement), 0.0)
        let downwardMovementPercent = fminf(downwardMovement, 1.0)
        let progress = CGFloat(downwardMovementPercent)

        guard let interactor = interactor else { return }

        switch sender.state {

        case .began:
            interactor.hasStarted = true
            self.dismiss(animated: true, completion: nil)

        case .changed:

            // alterar se o tamanho do presentigViewController (MainTabBarController) for alterado no background
            let scaleX = 0.95 + (progress * (1 - 0.95))
            let scaleY = 0.95 + (progress * (1 - 0.95))

            // Não deixa ultrapassar os 100% de scale (tamanho original)
            if (scaleX > 1 && scaleY > 1) { return }
            presentingViewController?.view.transform = CGAffineTransform.identity.scaledBy(x: scaleX, y: scaleY);
            presentingViewController?.view.layer.masksToBounds = true

            interactor.shouldFinish = progress > percentThreshold
            interactor.update(progress)

        case .cancelled:
            interactor.hasStarted = false
            interactor.cancel()

        case .ended:
            interactor.hasStarted = false
            if (interactor.shouldFinish) {
                interactorFinish(interactor: interactor)
            } else {

                // repõe o MainTabBarController na posição dele atrás do NewPostController
                UIView.animate(withDuration: 0.5, animations: {
                    self.presentingViewController?.view.transform = CGAffineTransform.identity.scaledBy(x: 0.95, y: 0.95);
                    self.presentingViewController?.view.layer.masksToBounds = true
                    let c = UIColor.black.withAlphaComponent(0.4)
                    let shadowView = self.presentingViewController?.view.viewWithTag(999)
                    shadowView?.backgroundColor = c
                })
                interactor.cancel()
            }

        default: break
        }
    }


    @objc func interactorFinish(interactor: Interactor) {
        removeShadow()
        interactor.finish()
    }

    // remove a shadow view
    @objc func removeShadow() {
        UIView.animate(withDuration: 0.2, animations: {
            self.presentingViewController?.view.transform = CGAffineTransform.identity.scaledBy(x: 1.0, y: 1.0);
            self.presentingViewController?.view.layer.masksToBounds = true

        }) { _ in
        }
    }
}

这是一个包含自定义演示文稿的帮助程序文件:

//
//  Helper.swift
//  dismissLayerTest
//
//  Created by Ivan Cantarino on 27/09/17.
//  Copyright © 2017 Ivan Cantarino. All rights reserved.
//

import Foundation
import UIKit

class Interactor: UIPercentDrivenInteractiveTransition {
    @objc var hasStarted = false
    @objc var shouldFinish = false
}


extension UIView {
    @objc func anchor(top: NSLayoutYAxisAnchor?, left: NSLayoutXAxisAnchor?, bottom: NSLayoutYAxisAnchor?, right: NSLayoutXAxisAnchor?, paddingTop: CGFloat, paddinfLeft: CGFloat, paddingBottom: CGFloat, paddingRight: CGFloat, width: CGFloat, height: CGFloat) {
        translatesAutoresizingMaskIntoConstraints = false
        if let top = top {
            topAnchor.constraint(equalTo: top, constant: paddingTop).isActive = true
        }
        if let left = left {
            leftAnchor.constraint(equalTo: left, constant: paddinfLeft).isActive = true
        }
        if let bottom = bottom {
            bottomAnchor.constraint(equalTo: bottom, constant: -paddingBottom).isActive = true
        }
        if let right = right {
            rightAnchor.constraint(equalTo: right, constant: -paddingRight).isActive = true
        }
        if width != 0 {
            widthAnchor.constraint(equalToConstant: width).isActive = true
        }
        if height != 0 {
            heightAnchor.constraint(equalToConstant: height).isActive = true
        }
    }

    @objc func roundCorners(corners:UIRectCorner, radius: CGFloat) {
        let path = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
        let mask = CAShapeLayer()
        mask.path = path.cgPath
        self.layer.mask = mask
    }
}



class CustomAnimationForDismisser: NSObject, UIViewControllerAnimatedTransitioning {

    // Tempo da animação
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.27
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        // Get the set of relevant objects.
        let containerView = transitionContext.containerView
        guard let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from) else {
            print("Returning animateTransition VC")
            return
        }
        // from view só existe no dismiss
        guard let fromView = transitionContext.view(forKey: UITransitionContextViewKey.from) else {
            print("Failed to instantiate fromView: CustomAnimationForDismisser()")
            return
        }
        // Set up some variables for the animation.
        let containerFrame: CGRect = containerView.frame
        var fromViewFinalFrame: CGRect = transitionContext.finalFrame(for: fromVC)
        fromViewFinalFrame = CGRect(x: 0, y: containerFrame.size.height, width: containerFrame.size.width, height: containerFrame.size.height)

        // Animate using the animator's own duration value.
        UIView.animate(withDuration: 0.4, delay: 0, options: .curveEaseOut, animations: {
            fromView.frame = fromViewFinalFrame
        }) { (finished) in
            let success = !(transitionContext.transitionWasCancelled)
            // Notify UIKit that the transition has finished
            transitionContext.completeTransition(success)
        }
    }
}



class CustomAnimationForPresentor: NSObject, UIViewControllerAnimatedTransitioning {
    // Tempo da animação
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.2
    }
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        // Get the set of relevant objects.
        let containerView = transitionContext.containerView

        // obtém os VCs para não o perder na apresentação (default desaparece por trás)
        guard let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from) else {//, let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to) else {
            print("Returning animateTransition VC")
            return
        }
        // gets the view of the presented object
        guard let toView = transitionContext.view(forKey: UITransitionContextViewKey.to) else { return }

        // Set up animation parameters.
        toView.transform = CGAffineTransform(translationX: 0, y: containerView.bounds.height)

        // Always add the "to" view to the container.
        containerView.addSubview(toView)

        // Animate using the animator's own duration value.
        UIView.animate(withDuration: 0.35, delay: 0, options: .curveEaseOut, animations: {
            // Zooms out da MainTabBarController - o VC
            fromVC.view.transform = CGAffineTransform(scaleX: 0.95, y: 0.95)
            // propriedades declaradas no CustomPresentationController() // Anima o presented view
            toView.transform = .identity
        }, completion: { (finished) in
            let success = !(transitionContext.transitionWasCancelled)
            // So it avoids view stacks and overlap issues
            if (!success) { toView.removeFromSuperview() }
            // Notify UIKit that the transition has finished
            transitionContext.completeTransition(success)
        })
    }
}

class CustomPresentationController: UIPresentationController {
    override init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController!) {
        super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
    }

    // Tamanho desejado para o NewPostController
    override var frameOfPresentedViewInContainerView: CGRect {
        guard let containerBounds = containerView?.bounds else {
            print("Failed to instantiate container bounds: CustomPresentationController")
            return .zero
        }
        return CGRect(x: 0.0, y: 0.0, width: containerBounds.width, height: containerBounds.height)
    }
    // Garante que o frame do view controller a mostrar, se mantém conforme desenhado na função frameOfPresentedViewInContainerView
    override func containerViewWillLayoutSubviews() {
        presentedView?.frame = frameOfPresentedViewInContainerView
    }
}

这种预期效果也可以在其他应用中看到，例如 Music app、Stack Exchange/Overflow iOS App

有没有人知道如何实现这一点？我觉得我真的很接近实现它，但我找不到一种方法来保持 dismissed View 在屏幕上有一个层。

上面的项目可以找到here

非常感谢。 问候。

Answer 1

我建议 Apple(在您提供的动画屏幕 gif 中提供的帮助)不使用呈现的 View Controller 。如果是这样，呈现的 View Controller 将无法缩小其 View ——并且在关闭时，呈现的 View Controller 的 View 将完全消失。

我会说这个接口(interface)的底层是一个带有多个 subview Controller 的父 View Controller (或者可能只是一个带有两个 subview 的普通 View Controller )。因此，我们可以随心所欲地显示这两个 subview 。您的动画 gif 显示了两个 subview 的两种可能排列方式:重叠，一个在另一个之上，第二个 View 从屏幕底部几乎看不到。