XF 列表视图事件

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:App30"
             x:Class="App30.MainPage">
    <StackLayout>
    <ListView x:Name="myListView" ItemSelected="myListView_ItemSelected" ItemTapped="myListView_ItemTapped"
              Refreshing="myListView_Refreshing"></ListView>
        <Button Text="Refresh" Clicked="Button_Clicked"></Button>
    </StackLayout>
</ContentPage>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace App30
{
 public partial class MainPage : ContentPage
 {
  public MainPage()
  {
   InitializeComponent();
            myListView.ItemsSource = new string[]
            {
                "zhangsan","lisi","wangwu","zhaoliu"
            };
            myListView.IsPullToRefreshEnabled = true;
  }

        private void myListView_ItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            //DisplayAlert("你选择了", e.SelectedItem.ToString(), "Ok");
        }

        private void myListView_ItemTapped(object sender, ItemTappedEventArgs e)
        {
            DisplayAlert("你选择了", e.Item.ToString(), "Ok");
        }

        private void myListView_Refreshing(object sender, EventArgs e)
        {
            myListView.ItemsSource = new string[]
           {
                "abc","123","hij","888"
           };
            myListView.EndRefresh();
        }

        private void Button_Clicked(object sender, EventArgs e)
        {
            myListView.BeginRefresh();
        }
    }
}