Windows 8 Store Apps学习(45) 多线程之异步编程: IAsyncAction

多线程之异步编程: IAsyncAction, IAsyncOperation

重新想象 Windows 8 Store Apps (45) - 多线程之异步编程: IAsyncAction, IAsyncOperation, IAsyncActionWithProgress, IAsyncOperationWithProgress

介绍

重新想象 Windows 8 Store Apps 之 异步编程

IAsyncAction - 无返回值，无进度值

IAsyncOperation - 有返回值，无进度值

IAsyncActionWithProgress - 无返回值，有进度值

IAsyncOperationWithProgress - 有返回 值，有进度值

示例

1、演示 IAsyncAction（无返回值，无进度值）的用法

Thread/Async/IAsyncActionDemo.xaml

<Page
    x:Class="XamlDemo.Thread.Async.IAsyncActionDemo"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Thread.Async"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="120 0 0 0">

            <TextBlock Name="lblMsg" FontSize="14.667" />

            <Button Name="btnCreateAsyncAction" Content="执行一个 IAsyncAction" Click="btnCreateAsyncAction_Click_1" Margin="0 10 0 0" />

            <Button Name="btnCancelAsyncAction" Content="取消" Click="btnCancelAsyncAction_Click_1" Margin="0 10 0 0" />

        </StackPanel>
    </Grid>
</Page>

Thread/Async/IAsyncActionDemo.xaml.cs

/*
 * 演示 IAsyncAction（无返回值，无进度值）的用法
 *
 * 注：
 * 1、WinRT 中的异步功能均源自 IAsyncInfo
 * 2、IAsyncAction, IAsyncOperation<TResult>, IAsyncActionWithProgress<TProgress>, IAsyncOperationWithProgress<TResult, TProgress> 均继承自 IAsyncInfo
 *
 *
 * 另：
 * Windows.System.Threading.ThreadPool.RunAsync() - 返回的就是 IAsyncAction
 */

using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace XamlDemo.Thread.Async
{
    public sealed partial class IAsyncActionDemo : Page
    {
        private IAsyncAction _action;

        public IAsyncActionDemo()
        {
            this.InitializeComponent();
        }

        private IAsyncAction GetAsyncAction()
        {
            // 通过 System.Runtime.InteropServices.WindowsRuntime.AsyncInfo 创建 IAsyncAction
            return AsyncInfo.Run(
                (token) => // CancellationToken token
                    Task.Run(
                        () =>
                        {
                            token.WaitHandle.WaitOne(3000);
                            token.ThrowIfCancellationRequested();
                        },
                        token));
        }

        private void btnCreateAsyncAction_Click_1(object sender, RoutedEventArgs e)
        {
            _action = GetAsyncAction();

            // 可以 await _action 

            // IAsyncAction 完成后
            _action.Completed =
                (asyncInfo, asyncStatus) => // IAsyncAction asyncInfo, AsyncStatus asyncStatus
                {
                    // AsyncStatus 包括：Started, Completed, Canceled, Error
                    lblMsg.Text = "完成了，AsyncStatus: " + asyncStatus.ToString();
                };

            lblMsg.Text = "开始执行，3 秒后完成";
        }

        // 取消 IAsyncAction
        private void btnCancelAsyncAction_Click_1(object sender, RoutedEventArgs e)
        {
            if (_action != null)
                _action.Cancel();
        }
    }
}

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