ios - UIAlertController : UICollectionViewFlowLayout is not defined warning every time I try to bringup a UIAlertcontroller

Question

我正在使用 UIAlertController 获取用户输入并更新表格单元格。每次当我尝试创建警报时，我都会在控制台中收到以下警告

2015-11-19 17:51:42.034 SimpleTableView[5488:584215] the behavior of the UICollectionViewFlowLayout is not defined because:

2015-11-19 17:51:42.035 SimpleTableView[5488:584215] the item height must be less than the height of the UICollectionView minus the section insets top and bottom values, minus the content insets top and bottom values.

2015-11-19 17:51:42.036 SimpleTableView[5488:584215] The relevant UICollectionViewFlowLayout instance is <_UIAlertControllerCollectionViewFlowLayout: 0x7fd0a057c3d0>, and it is attached to ; layer = ; contentOffset: {0, 0}; contentSize: {0, 0}> collection view layout: <_UIAlertControllerCollectionViewFlowLayout: 0x7fd0a057c3d0>. 2015-11-19 17:51:42.036 SimpleTableView[5488:584215] Make a symbolic breakpoint at UICollectionViewFlowLayoutBreakForInvalidSizes to catch this in the debugger.

如许多博客中所述，实现非常简单，

func displayAlertInfo(){
    let alertController = UIAlertController(title: "New Race", message: "Type in a new race", preferredStyle: .Alert)
    let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { (_) in
        alertController.dismissViewControllerAnimated(true, completion: nil)
    }
    let addAction = UIAlertAction(title: "Add", style: .Default) { (_) in
        let textFieldInput = alertController.textFields![0] as UITextField
        let newRace = textFieldInput.text?.capitalizedString
        DataManager.sharedInstance.addRace(species: self.species, race: newRace!)
        let newIndexPath = NSIndexPath(forRow: self.races.count - 1, inSection: 0)
        self.racesTableVew.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
    }

    alertController.addTextFieldWithConfigurationHandler { (textField) -> Void in
        textField.placeholder = "New Race"
    }

    alertController.addAction(cancelAction)
    alertController.addAction(addAction)

    self.presentViewController(alertController, animated: true, completion: nil)
}

我在点击导航按钮时调用此函数。警报显示正确，但每次我尝试点击创建警报的按钮时，我都会收到此警告。 我做错了什么或者我跳过了什么？

编辑:添加屏幕截图:通过 tableView 从导航项按钮调用警报。

Answer 1

你需要打电话

alertcontroller.view.setNeedsLayout()

就在

self.presentViewController(alertController, animated: true, completion: nil)

来源:https://forums.developer.apple.com/thread/18294 (最后一个答案)