依赖于第一个组件的 UIPickerView 不会更新 UI

Question

I want to build a UIPicker with nested data and 2 Components. The 2nd Component should be dependent on the selection of the 1st Component (eg when selected fruits -> display banana, apple...; when selected vegetables -> display tomatoes...).

This works, but the UI of the 2nd Component is not updated directly. I have to tap the 2nd Component to see the Titles. I tried to update the Component ( picker.reloadComponent(1) )and also AllComponents picker.reloadAllComponents() after Selection.

Any ideas?

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

    @IBOutlet weak var picker: UIPickerView!

    var plants = [Dictionary<String, Any>]()
    var groups:[String] = [String]()

    override func viewDidLoad() {
        super.viewDidLoad()

        plants.append([
            "name": "Fruits",
            "groups": [
                "Banana",
                "Apple"
            ]
        ])
        plants.append([
            "name": "Veggies",
            "groups": [
                "Tomatoe",
                "Salad",
                "Cucumber"
            ]
        ])

        if plants[0]["groups"] != nil {
            groups = plants[0]["groups"] as! Array
        }

        picker.delegate = self
        picker.dataSource = self
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 2
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        if component == 0 {
            return plants.count
        } else if component == 1 {
            return groups.count
        }

        return 0
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        if component == 0 {
            // Update groups array, based on selection
            if plants[row]["groups"] != nil {
                groups = plants[row]["groups"] as! Array
            }

            picker.reloadComponent(1) //also tried picker.reloadAllComponents() here
        }
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        if component == 0 {
            if plants[row]["name"] != nil {
                return plants[row]["name"] as! String
            }
        } else if component == 1 {
            // return values of current group
            return groups[row]
        }

        return ""
    }
}

Thanks in advance!

Answer 1

Swift 4.2 / xCode 10

Your code works fine. If your problem is that you want the second component be reloaded to its first item, try this after picker.reloadComponent(1) :

picker.selectRow(0, inComponent: 1, animated: true)

Otherwise please be more specific about the problem.