swift - Swift：将 UIBarButtonItem 设置为无需点击的弹出窗口的源？

Question

我想在我的视图加载后立即在 iPad 上显示一个弹出窗口，并将右上角的按钮作为源。弹出窗口在按钮点击时正确显示，但是当页面首次加载时，我无法找到一种在没有按钮点击的情况下显示它的方法。这可能吗？

这就是我所拥有的：

func displayOptions(sourceButton: UIBarButtonItem)
    let actionSheet = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
    if let popoverController = actionSheet.popoverPresentationController {
        var rect = CGRect(x: 0, y: 0, width: 0, height: 0)              
        popoverController.barButtonItem = sourceButton              
        popoverController.sourceRect = rect 
        popoverController.permittedArrowDirections = .up
    }
    viewController.present(actionSheet, animated: true, completion: nil)
}

此代码在按钮点击时正常工作，但如果我尝试从 viewDidLoad 或 viewDidAppear 调用此函数，应用程序会崩溃：

您必须通过警报控制器的 popoverPresentationController 提供此弹出窗口的位置信息。您必须提供 sourceView 和 sourceRect 或 barButtonItem。

Answer 1

1. 您需要提供sourceView.

2. UIAlertController必须有 a title、 amessage或要显示的操作。

   // Create a bar button item in ViewDidLoad.
   let button1 = UIBarButtonItem(image: UIImage(named: "imagename"), style: .plain, target: self, action: Selector("action"))
   self.navigationItem.rightBarButtonItem  = button1
   
   
   // Call in ViewDidLoad
   displayOptions(sourceButton: button1)
   
   func displayOptions(sourceButton: UIBarButtonItem) {
       let actionSheet = UIAlertController(title: "title", message: "message", preferredStyle: .actionSheet)
       if let popoverController = actionSheet.popoverPresentationController {
         let rect = CGRect(x: 0, y: 0, width: 0, height: 0)
         popoverController.barButtonItem = sourceButton
         popoverController.sourceRect = rect
         popoverController.sourceView = self.view
         popoverController.permittedArrowDirections = .up
       }
       self.present(actionSheet, animated: true, completion: nil)
   }
   

Answer 2

尝试使用 UIPopoverPresentationControllerDelegate

代码示例：

• viewDidLoad

  let buttonCustom = UIBarButtonItem(title: "Custom", style: .done, target: self, action: #selector(ViewController.customBarButtonAction))
  self.navigationItem.rightBarButtonItem  = buttonCustom
  displayOptions()
  

• 显示选项

  func displayOptions() {
      let actionSheet = UIAlertController(title: "Title", message: "Message", preferredStyle: .actionSheet)
      if let popoverController = actionSheet.popoverPresentationController {
          let rect = CGRect(x: 0, y: 0, width: 0, height: 0)
          popoverController.sourceRect = rect
          popoverController.sourceView = self.view
          popoverController.permittedArrowDirections = .up
          popoverController.delegate = self
      }
      self.present(actionSheet, animated: true, completion: nil)
  }
  

• 使用 UIPopoverPresentationControllerDelegate

  func prepareForPopoverPresentation(_ popoverPresentationController: UIPopoverPresentationController) {
      popoverPresentationController.barButtonItem = self.navigationItem.rightBarButtonItem
  }