Question

我使用外部委托文件来处理所有UICollectionView的处理，并且我努力让集合视图单元基于所选单元格通过委托文件执行segue

这是我目前在委托文件中的内容：

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)
    let mainController = MainController()
    mainController.performSegue(withIdentifier: "detailSegue", sender: cell)


}

在主控制器上我有：

override func performSegue(withIdentifier identifier: String, sender: Any?) {
    if identifier == "detailSegue" {
        let detailController = DetailController()
        self.present(detailController, animated: true)
    }
}

我得到的错误：

Warning: Attempt to present <DetailController: 0x7fbed8e6e4b0> on <MainController: 0x7fbedda79830> whose view is not in the window hierarchy!

我以为我可以通过委托来调用引用，它会显示控制器。

由于

Answer 1

您试图获得的MainController的引用是错误的。

let mainController = MainController()

这不会为您提供对象的加载/预览实例而不是它将为您创建MainController的新对象，而不是在预览层次结构中。所以你需要一个实际的预览实例。

<强>解决方案在委托类中创建UIViewController类型的全局对象，并传递预览类引用，以便在需要时使用它。

实施例

class DelegateDataSource: NSObject {
    var viewController: UIViewController?
    //Other Methods/Objects that you need.
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)
    if let mainController = viewController as? MainController {
         mainController.performSegue(withIdentifier: "detailSegue", sender: cell)
    }



}
}

class MainController: UIViewController {

    var delegateDataSource: DelegateDataSource?
    func initializeDelegates() {
         //Initialize you datasource object and do some tasks that you need and then assign your current instance to this class like this.
         delegateDataSource.viewController = self
    }

}

Answer 2

    static void Main(string[] args)
    {
        Console.WriteLine(SixDigitPalindromeWithDivisor().ToString());
        Console.ReadLine();
    }

    public static int SixDigitPalindromeWithDivisor()
    {
        for (int i = 999; i > 100; i--)
        {
            //generating palindrome number from max
            var palindromeInt = Int32.Parse(Convert.ToString(i) + ReverseString(Convert.ToString(i)));

            //checking three digit number factor exist
            if (CheckThreeDigitDivisorExists(palindromeInt))
            {
                return palindromeInt;
            }
        }
        return 0;
    }

    public static bool CheckThreeDigitDivisorExists(int number)
    {
        for (int i = 999; i > 100; i--)
        {
            if (number % i == 0)
            {
                if (number / i <= 999)
                {
                    return true;
                }
            }
        }
        return false;
    }

    public static string ReverseString(string s)
    {
        char[] arr = s.ToCharArray();
        Array.Reverse(arr);
        return new string(arr);
    }

这不起作用，使用委托模式或使用单一模式为您的MainController。

Answer 3

只有已经呈现的控制器才能显示另一个控制器。实施Traceback (most recent call last): File "<input>", line 2, in <module> File "/home/vincent/anaconda3/envs/my_env/lib/python3.5/codecs.py", line 321, in decode (result, consumed) = self._buffer_decode(data, self.errors, final) UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte的班级是didSelectItemAt吗？如果是这样，为什么不这样做：

UIViewController

Swift UICollectionView委托执行segue

3 个答案: