XF 进度条和指示器

<?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:App23"
             x:Class="App23.MainPage">

    <StackLayout VerticalOptions="Center">
        <ProgressBar x:Name="pb" Progress="0.1"></ProgressBar>
        <ActivityIndicator x:Name="ai"></ActivityIndicator>
        <Button Text="start" 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 App23
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
        }

        private void Button_Clicked(object sender, EventArgs e)
        {
            pb.ProgressTo(1, 1000, Easing.Linear);
            ai.IsRunning = !ai.IsRunning;
        }
    }
}