Question

现在我收到错误：警告：尝试在CollectionViewController上呈现UIAlertController：0x7f9af9016200：0x7f9af750d620已经呈现（null）

我可以在swift中堆叠警报吗？有我的代码，如果项目超过前一天发布，它会显示警报。有两种方法我试图这样做但没有成功。

暂停for循环直到我按是或否。
在彼此之上呈现许多提醒

任何解决方案如何设法做到这一点？

for p in json! {
     if self.checkDaysPassed(postDate: p["uploadedTime"] as! String) > 1 {
     print("more than one day passed, sell item?")

     let alert = UIAlertController(title: "Sell this item", message: "This item has been unused for a day", preferredStyle: .alert)
     alert.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext
     alert.addAction(UIAlertAction(title: "Yes", style: .default){ (action) in
           print("pressed yes")
     })
     alert.addAction(UIAlertAction(title: "No", style: .cancel){ (action) in
          print("pressed no")
     })
     self.present(alert, animated: true)
    }
}

Answer 1

要在彼此之后显示警报，我建议添加此递归代码，

为class添加messages变量，并为所有array条件填充true。之后，您必须调用showAlert方法，该方法将逐个显示所有消息。

class YourClass {

   var messages: [String] = []


   func yourMethod() {
       for p in json! {
         if self.checkDaysPassed(postDate: p["uploadedTime"] as! String) > 1 {
             messages.append("This item has been unused for a day")
         }
       }
       self.showAlert()
   }

   private func showAlert() {
        guard self.messages.count > 0 else { return }

        let message = self.messages.first

        func removeAndShowNextMessage() {
            self.messages.removeFirst()
            self.showAlert()
        }

        let alert = UIAlertController(title: "Sell this item", message: message, preferredStyle: .alert)
        alert.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext
        alert.addAction(UIAlertAction(title: "Yes", style: .default){ (action) in
            print("pressed yes")
            removeAndShowNextMessage()

        })
        alert.addAction(UIAlertAction(title: "No", style: .cancel){ (action) in
            print("pressed no")
            removeAndShowNextMessage()
        })

        UIApplication.shared.delegate?.window??.rootViewController?.present(alert, animated: true)
    }
}

在swift中相互重叠的多个警报

1 个答案: