title: Ionic v4.12 ion-picker can not find any way to handle item selected change of a column
body: <p>I user ion-picker component with ionic V4.12, and I have 3 columns. When I select one item of the first column, I need to filter items of the second column, but I cannot find any way to resolve my problem</p>
  
  <p>I found PickerColumn has refresh function ,but still not work</p>
  
  <pre><code>import { PickerController } from '@ionic/angular';
  
  @Component({
    ...
  })
  export class ComponentPage {
    constructor(public pickerCtrl: PickerController) { }
  
    async openPicker() {
      const picker = await this.pickerCtrl.create({
        buttons: [{
          text: 'Done',
        }],
        columns: [
          {
            name: 'days',
            options: [
              {
                text: '1',
                value: 1
              },
              {
                text: '2',
                value: 2
              },
              {
                text: '3',
                value: 3
              },
            ]
          },
          {
            name: 'years',
            options: [
              {
                text: '1992',
                value: 1992
              },
              {
                text: '1993',
                value: 1993
              },
              {
                text: '1994',
                value: 1994
              },
            ]
          },
        ]
      });
      await picker.present();
    }
  }
  </code></pre>
  
  <p>When I select 1 on days column, I just want to show the item named 1994.</p>