Question

下面： -

导入UIKit

类ViewController：UIViewController，UIPickerViewDataSource，UIPickerViewDelegate { @IBOutlet弱var statePicker：UIPickerView！

@IBOutlet weak var statepickerbtn: UIButton!

let states = ["alaska","alabama","akansas","california","maine","new york"]

override func viewDidLoad() {
    super.viewDidLoad()
    statePicker.dataSource = self
    statePicker.delegate = self
    // 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 statebtnpressed(_ sender: Any) {

    func numberOfComponents(in: <#T##UIPickerView#>)-> Int
    {
        return 1
    }
    func pickerView(<#T##pickerView: UIPickerView##UIPickerView#>, numberOfRowsInComponent: <#T##Int#>)->Int
    {
        return states.count
    }


    func pickerView(<#T##pickerView: UIPickerView##UIPickerView#>, titleForRow: <#T##Int#>, forComponent: <#T##Int#>) -> String?
    {
        return states[row]
    }

}

}

Answer 1

您正在错误的地方添加委托方法。不要将选择器委托方法放在按钮操作中。

class ViewController : UIViewController,UIPickerViewDataSource,UIPickerViewDelegate { 

   @IBOutlet weak var statepickerbtn: UIButton!
   @IBOutlet weak var statePicker: UIPickerView!
   let states = ["alaska","alabama","akansas","california","maine","new york"]

   override func viewDidLoad() {
    super.viewDidLoad()
    statePicker.dataSource = self
    statePicker.delegate = self
    // 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 statebtnpressed(_ sender: Any) { 
  //Do not place delegates method inside this action method. Instead of this use show hide procedure on picker view.

   }

public func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
}

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

}

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

}

xcode显示错误编译代码

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