选择器视图不加载项目

Question

我目前遇到pickerview的问题，因为当我单击应用程序时，选择器视图未从Web服务加载的玩法测验。选择器视图应显示来自Web服务的答案数组。选择器视图是空的任何想法？另外问题是不是从Web服务加载为文本标签？

class QuestionsViewController: UIViewController, UIPickerViewDelegate { 

@IBOutlet weak var usernamelabel: UILabel! 
@IBOutlet weak var itemlabel: UILabel! 
@IBOutlet weak var Question: UILabel! 
@IBOutlet weak var pickerview: UIPickerView! 

public var totalQuestions: Int = 0 
public var currentQuestion = 0 
public var totalCorrect: Int = 0 
var itemSelected: String = "" 
@IBOutlet weak var share: UIButton! 
var LabelText = String() 


var listQuestions = [[String: Any]]() 
var titles: [String] = [] 
var qnames: String = "" 

@IBOutlet weak var Next: UIButton! 
var quiz = QuestionList() 

override func viewDidLoad() { 
    super.viewDidLoad() //when the app is loaded 


    let url:String =  "https://api.mlab.com/api/1/databases/quiz/collections/question?apiKey=NT28RNl6jX3Ys0x5GJZ6mMSRQEcb_6KA" 

    let urlRequest = URL(string: url) 

    URLSession.shared.dataTask(with: urlRequest!, completionHandler: { 
     (data, response, error) in 
     if(error != nil){ 
      print(error.debugDescription) 
     } 
     else{ 
      do{ 
       self.listQuestions = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [[String:AnyObject]] 
       print(self.listQuestions) 

       for elements in self.listQuestions { 
        for object in elements { 
         if object.key == "Answers" { 
          if let answers = object.value as? [String] { 
           self.titles = answers 
          } 
          if object.key == "Questions" { 
           if let questions = object.value as? String { 
            self.qnames = questions 
           } 
          } 
         } 
        } 
       } 
       self.pickerview.reloadAllComponents() 

      }catch let error as NSError{ 
       print(error) 
      } 
     } 
    }).resume() 


} 


func numberOfComponents(in pickerView: UIPickerView) -> Int { 

    return 1 //return one component from the picker 
} 

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int{ 

    return titles.count 
} 

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) ->String?{ 


    return self.titles[row] 


} 

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){ 

    itemSelected = QuestionList.getDummyQuestions()[currentQuestion].answers[row] 

} 

@IBAction func btnShareClicked(_ sender: Any) { 
    if SLComposeViewController.isAvailable(forServiceType: SLServiceTypeFacebook) { 

     let fbShare:SLComposeViewController = SLComposeViewController(forServiceType:SLServiceTypeFacebook) 
     fbShare.setInitialText("You Scored " + itemlabel.text! + " on the IT Quiz") 
     self.present(fbShare, animated:true, completion:nil) 

    } else { 
     let alert = UIAlertController(title: "Account", message: "Please login to Facebook", 
             preferredStyle: UIAlertControllerStyle.alert) 

     alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler:nil)) 
     self.present(alert, animated: true, completion: nil) 

    } 


} 





} 

Answer 1

你ViewController缺少UIPickerViewDataSource协议：

class QuestionsViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {} 

确保pickerView的delegate和datasource被设置为当前viewController。

override func viewDidLoad() { 
    super.viewDidLoad() //when the app is loaded 

    pickerview.delegate = self 
    pickerview.dataSource = self 
} 

的dataTask是一个异步任务，您应该更新在主线程的UI。

DispatchQueue.main.async { 
    self.pickerview.reloadAllComponents() 
} 

最终的代码应该是这样的：

class QuestionsViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource { 

    @IBOutlet weak var usernamelabel: UILabel! 
    @IBOutlet weak var itemlabel: UILabel! 
    @IBOutlet weak var Question: UILabel! 
    @IBOutlet weak var pickerview: UIPickerView! 

    public var totalQuestions: Int = 0 
    public var currentQuestion = 0 
    public var totalCorrect: Int = 0 
    var itemSelected: String = "" 
    @IBOutlet weak var share: UIButton! 
    var LabelText = String() 


    var listQuestions = [[String: Any]]() 
    var titles: [String] = [] 
    var qnames: String = "" 

    @IBOutlet weak var Next: UIButton! 
    var quiz = QuestionList() 

    override func viewDidLoad() { 
     super.viewDidLoad() // when the app is loaded 

     pickerview.delegate = self 
     pickerview.dataSource = self 

     let url:String = "https://api.mlab.com/api/1/databases/quiz/collections/question?apiKey=NT28RNl6jX3Ys0x5GJZ6mMSRQEcb_6KA" 

     let urlRequest = URL(string: url) 

     URLSession.shared.dataTask(with: urlRequest!, completionHandler: { 
      (data, response, error) in 
      if(error != nil){ 
       print(error.debugDescription) 
      } 
      else{ 
       do{ 
        self.listQuestions = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [[String:AnyObject]] 
        print(self.listQuestions) 

        for elements in self.listQuestions { 
         for object in elements { 
          if object.key == "Answers" { 
           if let answers = object.value as? [String] { 
            self.titles = answers 
           } 
          } 
          if object.key == "Questions" { 
           if let questions = object.value as? String { 
            self.qnames = questions 
           } 
          } 
         } 
        } 

        DispatchQueue.main.async { 
         self.pickerview.reloadAllComponents() 
         self.Question.text = self.qnames 
        } 

       }catch let error as NSError{ 
        print(error) 
       } 
      } 
     }).resume() 
    } 


    func numberOfComponents(in pickerView: UIPickerView) -> Int { 
     return 1 //return one component from the picker 
    } 

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int{ 
     return titles.count 
    } 

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) ->String? { 
     return self.titles[row] 
    } 

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){ 

     itemSelected = QuestionList.getDummyQuestions()[currentQuestion].answers[row] 

    } 

    @IBAction func btnShareClicked(_ sender: Any) { 
     if SLComposeViewController.isAvailable(forServiceType: SLServiceTypeFacebook) { 

      let fbShare:SLComposeViewController = SLComposeViewController(forServiceType:SLServiceTypeFacebook) 
      fbShare.setInitialText("You Scored " + itemlabel.text! + " on the IT Quiz") 
      self.present(fbShare, animated:true, completion:nil) 

     } else { 
      let alert = UIAlertController(title: "Account", message: "Please login to Facebook", 
              preferredStyle: UIAlertControllerStyle.alert) 

      alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler:nil)) 
      self.present(alert, animated: true, completion: nil) 

     } 
    } 
} 

Answer 2

要获得问题标签：

for object in elements { 

     if let result = object["Questions"] as? [String: AnyObject] { 

      print(result) 

}