我有两个不同的问题，
- 我有一个隐藏在 viewDidLoad() 中的标签，稍后我试图将隐藏值设置为 false 但它不起作用。
- 尝试显示警报但收到此错误“由于未捕获的异常‘NSInvalidArgumentException’而终止应用程序，原因:‘应用程序试图以模态方式呈现事件 Controller ’
下面是我的代码
class HomeViewController: UIViewController ,UITextFieldDelegate {
@IBOutlet weak var userName: UITextField!
@IBOutlet weak var passWord: UITextField!
@IBOutlet weak var errorMessage: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
self.errorMessage.hidden = true
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
@IBAction func login(sender: AnyObject) {
let alertController = UIAlertController(title: "Error", message:
"Wrong username or password", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default,handler: nil))
let url = NSURL(string: "myurl")
let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
println(NSString(data: data, encoding: NSUTF8StringEncoding))
var error: NSError?
let jsonData: NSData = data /* get your json data */
let json = NSJSONSerialization.JSONObjectWithData(jsonData, options: nil, error: &error) as NSDictionary
if let login: AnyObject = json["login"] {
if (login as NSObject == 0){
self.errorMessage.hidden = false
self.presentViewController(alertController, animated: true, completion: nil)
}
}
}
task.resume()
}
最佳答案
好的，最后我使用 dispatch_async(dispatch_get_main_queue()) { } 解决了这个问题，所以 if 语句将是这样的
if let login: AnyObject = json["login"] {
if (login as NSObject == 0){
dispatch_async(dispatch_get_main_queue()) {
self.errorMessage.hidden = false
self.presentViewController(alertController, animated: true, completion: nil)
}
}
}
关于ios - 警报错误并动态显示隐藏的 UILabel，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28793844/