使用 UIPresentationController 实现自定义弹窗

   <p>UIPresentationController 是 iOS8 新增的一个 API，可以用它实现自定义的弹窗。但 UIPresentationController 的使用门槛比较高，需要实现几个类和相关代理。 Presentr 让这一切变得简单，轻松实现自定义警告窗、菜单或其他任何弹窗。如下图：</p>    <p style="text-align:center"><img src="https://simg.open-open.com/show/27896a8f445da53fd3aea140a918029c.png"></p>    <h3>Presentr 实现弹窗</h3>    <p>Presentr 提供了一个默认的弹窗类 AlertViewController，以下代码即可显示上面的弹窗：</p>    <pre>  <code class="language-objectivec">let presenter = Presentr(presentationType: .Alert)  presenter.transitionType = TransitionType.CrossDissolve    let controller = Presentr.alertViewController(title: title, body: body)  let cancelAction = AlertAction(title: "NO, SORRY! :scream:", style: .Cancel) { alert in      print("CANCEL!!")  }  let okAction = AlertAction(title: "DO IT! ��", style: .Destructive) { alert in      print("OK!!")  }  alertController.addAction(cancelAction)  alertController.addAction(okAction)    customPresentViewController(presenter, viewController: controller, animated: true, completion: nil)</code></pre>    <p>要实现自定义的窗口，只需将上面的 AlertViewController 换成我们自己的窗口类即可，如下的 SomeViewController。</p>    <pre>  <code class="language-objectivec">let alertController = SomeViewController()  customPresentViewController(presenter, viewController: alertController, animated: true, completion: nil)</code></pre>    <p>Presentr 提供了五种显示类型，如下</p>    <pre>  <code class="language-objectivec">public enum PresentationType {    case Alert    case Popup    case TopHalf    case BottomHalf    case Custom(width: ModalSize, height: ModalSize, center: ModalCenterPosition)  }</code></pre>    <p>通过 PresentationType.Custom 我们可自定义弹窗的大小</p>    <pre>  <code class="language-objectivec">let width = ModalSize.Custom(size: 320)  let height = ModalSize.Custom(size: 150)  let center = ModalCenterPosition.Center //CustomOrigin(origin: CGPoint(x: 0, y: 100))  let customType = PresentationType.Custom(width: width, height: height, center: center)    let customPresenter = Presentr(presentationType: customType)  customPresenter.transitionType = .CrossDissolve</code></pre>    <h3>Presentr 如何实现弹窗</h3>    <p>Presentr 封装了 UIPresentationController，UIViewControllerTransitioningDelegate，UIViewControllerAnimatedTransitioning，类图如下：</p>    <p style="text-align:center"><img src="https://simg.open-open.com/show/eaac3ee6ddb56e64a6c4b2b629b25b54.png"></p>    <p>首先要清楚两个概念：当前的窗口为 presentingViewController，即将显示的窗口为 presentedViewController。 主要函数调用步骤：</p>    <ol>     <li>在主窗口 UIViewController 中调用 customPresentViewController(presenter, viewController: alertController, animated: true, completion: nil)</li>     <li>Presentr： presentationControllerForPresentedViewController ，返回 PresentrController</li>     <li>Presentr： animationControllerForPresentedController</li>     <li>PresentrController： presentationTransitionWillBegin</li>     <li>PresentrController： frameOfPresentedViewInContainerView</li>     <li>PresentrController： containerViewWillLayoutSubviews</li>    </ol>    <p>第一步是 Presentr 对 UIPresentationController 细节封装后提供的 UIViewController 的扩展函数。我们只需要写这行代码，剩下的步骤都由 Presentr 完成。这里，Presentr 将设置 PresentedView 的代理 —— transitioningDelegate = self 。</p>    <p>第二步和第三步都是 UIViewControllerTransitioningDelegate 协议的函数，由 Presentr 实现。第二步完成 UIPresentationController 的 子类 PresentrController 的初始化。在初始化创建一个黑色半透明背景视图，如下</p>    <pre>  <code class="language-objectivec">init(presentedViewController: UIViewController, presentingViewController: UIViewController, presentationType: PresentationType, roundCorners: Bool, dismissOnTap: Bool) {          self.presentationType = presentationType          self.roundCorners = roundCorners          self.dismissOnTap = dismissOnTap            super.init(presentedViewController: presentedViewController, presentingViewController: presentingViewController)            setupChromeView()  }    private func setupChromeView() {      let tap = UITapGestureRecognizer(target: self, action: #selector(chromeViewTapped))      chromeView.addGestureRecognizer(tap)      chromeView.backgroundColor = UIColor(red: 0, green: 0, blue: 0, alpha: 0.7)      chromeView.alpha = 0  }</code></pre>    <p>第三步是 PresentedView 出现时的动画效果。苹果自带的动画有从底向上弹窗、渐隐渐现、翻转，Presentr 实现了两个自定义的动画效果：从左往右或从右往左，从上往下。如果需要其他动画效果需要自己实现。</p>    <p>第四步，在 PresentedView 显示之前，添加半透明视图 chromeView 到 PresentrController 的 containerView 中，并添加 chromeView 的显示动画</p>    <pre>  <code class="language-objectivec">override func presentationTransitionWillBegin() {      chromeView.frame = containerView!.bounds      chromeView.alpha = 0.0      containerView?.insertSubview(chromeView, atIndex: 0)        if let coordinator = presentedViewController.transitionCoordinator() {            coordinator.animateAlongsideTransition({ context in              self.chromeView.alpha = 1.0              }, completion: nil)        } else {          chromeView.alpha = 1.0      }  }</code></pre>    <p>第五步，设置 PresentedView 的 frame 大小。</p>    <p>第六步，在布局开始前，将第五步计算的 frame 赋值给 presentedView()!</p>    <pre>  <code class="language-objectivec">override func containerViewWillLayoutSubviews() {      chromeView.frame = containerView!.bounds      presentedView()!.frame = frameOfPresentedViewInContainerView()  }</code></pre>    <p>这样，我们自定义的弹窗就显示出来了。</p>    <p>使用 UIPresentationController 实现了逻辑的解耦，显示的工作全部交由 UIPresentationController 负责。presentedViewController 不需要提供一个半透明的背景视图，主窗口 presentingViewController 不需要对 presentedView 做额外的处理，只需要调用 present 即可。</p>    <p> </p>    <p>来自：http://www.jianshu.com/p/90bb6a2f8122</p>    <p> </p>