Question

我是初级程序员。我正在尝试向Alert上的按钮添加操作，但它不起作用。我只想测试警报按钮选项是否可以更改标签中的文本，但它不起作用。当然，我可以很好地看到警报和按钮，但点击按钮后没有任何反应。

@IBOutlet var statusLabelAlert : UILabel

var alertTest = UIAlertView()

@IBAction func alertButton(sender : AnyObject) {

    alertTest.message = "Select one!"
    alertTest.addButtonWithTitle("1st")
    alertTest.addButtonWithTitle("2nd")
    alertTest.addButtonWithTitle("3rd")
    alertTest.title = "Test Alert"
    alertTest.show()

}
func alertView(alertView: UIAlertView!, clickedButtonAtIndex buttonIndex: Int){
    switch buttonIndex{
    case 0:
        statusLabelAlert.text = "1st"
    case 1:
        statusLabelAlert.text = "2nd"
    case 2:
        statusLabelAlert.text = "3rd"
    default:
        statusLabelAlert.text = "error"
    }

}

Answer 1

你的clickedButtonAtIndex方法是否正在调用？设置断点并调试代码。您没有设置alertView的委托。

@IBOutlet var statusLabelAlert : UILabel

var alertTest = UIAlertView()
alertTest.delegate = self   //set the delegate of alertView

@IBAction func alertButton(sender : AnyObject) {

alertTest.message = "Select one!"
alertTest.addButtonWithTitle("1st")
alertTest.addButtonWithTitle("2nd")
alertTest.addButtonWithTitle("3rd")
alertTest.title = "Test Alert"
alertTest.show()

}
func alertView(alertView: UIAlertView!, clickedButtonAtIndex buttonIndex: Int){
switch buttonIndex{
case 0:
    statusLabelAlert.text = "1st"
case 1:
    statusLabelAlert.text = "2nd"
case 2:
    statusLabelAlert.text = "3rd"
default:
    statusLabelAlert.text = "error"
}

}

Answer 2

您必须设置警报视图的代理：

alertTest.delegate = self

UIAlertView使用delegate pattern，这意味着它调用其委托上的方法来实现某些事情或通知事件。对于UIAlertView，其中一个事件是用户点击按钮时。要使警报视图知道要告知用户的点击，您必须指定实现UIAlertViewDelegate协议的委托。您的代码实现了协议，但它从不告诉警报您希望成为其委托，因此您永远不会收到方法调用。

Answer 3

@IBOutlet var statusLabelAlert : UILabel
var alertTest = UIAlertView()
@IBAction func alertButton(sender : AnyObject)
{
    alertTest.delegate = self
    alertTest.message = "Select one!"
    alertTest.addButtonWithTitle("1st")
    alertTest.addButtonWithTitle("2nd")
    alertTest.addButtonWithTitle("3rd")
    alertTest.title = "Test Alert"
    alertTest.show()

}

func alertView(alertView: UIAlertView!, clickedButtonAtIndex buttonIndex: Int)
{
    switch buttonIndex
    {
        case 0:
        statusLabelAlert.text = "1st"
        case 1:
        statusLabelAlert.text = "2nd"
        case 2:
        statusLabelAlert.text = "3rd"
        default:
        statusLabelAlert.text = "error"
   }
}

Answer 4

如果是iOS 8，你应该切换到UIAlertController和UIAlertAction。 UIAlertAction包含按钮应该做的事情。

Answer 5

IBOutlet var statusLabelAlert : UILabel

@IBAction func alertButton(sender : AnyObject) {

let alert = UIAlertController(title: "Alert", message: "This is an Alert", preferredStyle: UIAlertControllerStyle.Alert)

alert.addAction(UIAlertAction(title: "1st", style: UIAlertActionStyle.Default, handler: { (action: UIAlertAction!) in
statusLabelAlert.text = "1st" 
}))

alert.addAction(UIAlertAction(title: "2nd", style: UIAlertActionStyle.Default, handler: { (action: UIAlertAction!) in
statusLabelAlert.text = "2nd" 
}))

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

}

如果您在按下按钮时不想做某事：

alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Default, handler: nil))

如何在Swift中的Alert中向按钮添加操作

5 个答案: