ios - 如何检测 UIPickerView 上的变化？

Question

我想检测 UIPickerView 值的变化。

如果 UIPickerView 响应 addTarget 我使用了这样的代码：

-(void) valueChange:(id)sender {
    change = YES;
} 

UIPickerView *questionPicker = [[UIPickerView alloc] init]; 
[questionPicker addTarget:self action:@selector(valueChange:) forControlEvents:UIControlEventValueChanged];

我怎样才能以正确的方式做同样的事情？

Answer 1

如果您查看UIPickerViewDelegate它有：

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component

只需设置您的选择器视图委托并实现它。

Answer 2

UIPickerViewDelegate有 pickerView:didSelectRow:inComponent:

Answer 3

更好地覆盖这个函数

public override func selectedRow(inComponent component: Int) -> Int {
  let index = super.selectedRow(inComponent: component)
  //call closure or delegate as you want
  return index
}

在UIPickerView类中实时观察变化。

Answer 4

Swift 4：实现选择器视图委托：

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

例子：

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, 
forComponent component: Int) -> String? {
            let value = dummyListArray[row]
            if value == "someText"{
              //Perform Action
            }
            return value
}

或者

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

例子：

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, 
inComponent component: Int) {
            let value = dummyListArray[row]
            if value == "someText"{
              //Perform Action
            }        
}

Answer 5

func pickerView(UIPickerView, didSelectRow: Int, inComponent: Int)

当用户选择组件中的一行时，由选取器视图调用。

例如，这允许在选择更改时更新文本字段，只需松开手指即可。

Answer 6

您必须使用选取器视图委托方法：

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