如何“等待”PopoverPresentationController 被关闭

Question

我正在编写一个 "notebook" 风格的程序。笔记本有多个页面，我试图放入一个 "go to page" 弹出窗口以允许用户转到任何页面。弹出窗口显示每个页面缩略图的集合视图。显然，最好是：

在弹出窗口中单击所需的页面缩略图
通过委托
让接收者 mainViewController 显示 selectedPage

弹出窗口效果很好。页面 selection 工作并将 selectedPage 传回。

问题是我需要 mainViewController "wait" 供用户 select 页面。这里是 mainViewController 中的相关代码部分：

用户 select 显示弹出窗口的 barButton：

@IBAction func selectPage(sender: UIBarButtonItem) {

        self.performSegueWithIdentifier("showPages", sender: self)

    //need to wait here for the popover to be dismissed.
//the next line is executed before segue even appears
//"while" and delay don't work

    imageView.image = currentNotebook.pages[goToPage! - 1] //displays selectedPage (goToPage is set by delegation)
    goToPage = nil
}

//跳转到弹出框

case "showPages" :
            let navigationController = segue.destinationViewController as? PageCollectionViewController

                if let vc = navigationController {
                    vc.delegate = self
                    vc.modalInPopover = false
                    vc.preferredContentSize = CGSizeMake(400,100)
                    vc.notebook = self.currentNotebook
                    print("got to show pages")
        }

我怀疑 selectPage 函数中需要某种闭包或处理程序，但我想不出来。希望这已经足够清楚了。一大早的...

弹出窗口的代码如下：

import UIKit

protocol PageCollectionViewControllerDelegate {
func selectsPage(selectedPage:Int)
}

class PageCollectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate  {

var notebook: Notebook!
var pageNum: Int!
var delegate: PageCollectionViewControllerDelegate?

@IBOutlet weak var pageCollectionView: UICollectionView!

override func viewDidLoad() {
    super.viewDidLoad()

    self.pencilCollectionView!.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "cell")

    // Do any additional setup after loading the view.
}

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

func numberOfSectionsInCollectionView(pageCollectionView: UICollectionView) -> Int {    
    return 1
}


func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    return notebook.pages.count
}

func collectionView(pageCollectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell = pageCollectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! PageCollectionViewCell
    let cellImage = notebook.pages[indexPath.row]
    let tempThumb = imageWithImage(cellImage, scaledToFillSize: CGSizeMake(cell.bounds.width, cell.bounds.height)) //create thumbnail of each page

    cell.pageThumb.image = tempThumb
    cell.backgroundColor = UIColor.whiteColor()

    return cell
}

func collectionView(pageCollectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {

    //return page number

    if let delegate =  self.delegate {
        pageNum = indexPath.row + 1
        print("page number",pageNum)

        delegate.selectsPage(pageNum)
    }
    self.dismissViewControllerAnimated(true, completion: nil) //if you comment this out the popover is  not dismissed when clicking on a cell
}


func imageWithImage(image: UIImage, scaledToFillSize size: CGSize) -> UIImage {
    let scale: CGFloat = max(size.width / image.size.width, size.height / image.size.height)
    let width: CGFloat = image.size.width * scale
    let height: CGFloat = image.size.height * scale
    let imageRect: CGRect = CGRectMake((size.width - width) / 2.0, (size.height - height) / 2.0, width, height)
    UIGraphicsBeginImageContextWithOptions(size, false, 0)
    image.drawInRect(imageRect)
    let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
}

}

Answer 1

这是一个典型的异步编程的例子。在这种情况下，您正在等待的异步事件是用户响应。

几乎普遍的答案是"don't wait. Send a message and have the event notify you when it's done."

我要做的是创建一个 UIViewController 的自定义子类作为您的弹出窗口，然后为弹出窗口提供一个完成块（闭包）属性，或者使用委托对其进行设置，然后定义一个协议，以便当用户选择一个选项时弹出窗口可以通知它的委托。（这两种方法非常相似，但是有了完成块，您不必定义被调用的方法 - 您只需在调用弹出窗口时传入完成代码即可。）

如何“等待”PopoverPresentationController 被关闭

How to "wait' for a PopoverPresentationController to be dismissed

uipopovercontroller

ios

swift