选择器视图未加载项目

Question

我目前在使用 pickerview 时遇到问题，因为当我在应用程序上单击 play quiz 时，picker view 根本没有从 Web 服务加载。选择器视图应显示来自 Web 服务的答案数组。选择器视图是空的有什么想法吗？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

您的ViewController 缺少UIPickerViewDataSource 协议：

class QuestionsViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {}

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

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

    pickerview.delegate = self
    pickerview.dataSource = self
}

dataTask 是一个异步任务，你应该在主线程上更新 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

获取问题标签：

for object in elements {

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

           print(result)

}