重新想象 Windows 8 Store Apps (42) - 多线程之线程池: 延迟执行, 周期执行, 在线程池中找一个线程去执行指定的方法

<Page
    x:Class="XamlDemo.Thread.ThreadPool.DelayTimer"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Thread.ThreadPool"
    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="btnCreateDelay" Content="延迟 3 秒后执行一个任务" Click="btnCreateDelay_Click_1" Margin="0 10 0 0" />

            <Button Name="btnCancelDelay" Content="取消任务" Click="btnCancelDelay_Click_1" Margin="0 10 0 0" />

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

/*
 * 通过 ThreadPoolTimer 实现延迟执行（ThreadPoolTimer 在 Windows.System.Threading 命名空间下）
 * 
 * ThreadPoolTimer - 计时器
 *     ThreadPoolTimer CreateTimer(TimerElapsedHandler handler, TimeSpan delay, TimerDestroyedHandler destroyed); - 创建一个用于延迟执行的计时器
 *         handler - 指定的延迟时间过后，所需要执行的方法
 *         delay - 延迟时间
 *         destroyed - 当 ThreadPoolTimer 完成了自身的使命后所执行的方法（比如延迟方法执行完了或计时器被取消了）
 *     Cancel() - 取消计时器
 *     Delay - 延迟时间，只读
 */

using System;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.System.Threading;
using Windows.UI.Core;

namespace XamlDemo.Thread.ThreadPool
{
    public sealed partial class DelayTimer : Page
    {      
        private ThreadPoolTimer _timer;

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

        // 创建一个延迟计时器
        private void btnCreateDelay_Click_1(object sender, RoutedEventArgs e)
        {
            _timer = ThreadPoolTimer.CreateTimer(
                (timer) => 
                {
                    var ignored = Dispatcher.RunAsync(CoreDispatcherPriority.High,
                        () =>
                        {
                            lblMsg.Text = "任务执行了";
                        });
                },
                TimeSpan.FromSeconds(3), 
                (timer) => 
                {
                    var ignored = Dispatcher.RunAsync(CoreDispatcherPriority.High,
                        () =>
                        {
                            lblMsg.Text += Environment.NewLine;
                            lblMsg.Text += "ThreadPoolTimer 的使命结束了";
                        });
                });

            lblMsg.Text = "延迟 3 秒后执行一个任务";
        }

        // 取消计时器
        private void btnCancelDelay_Click_1(object sender, RoutedEventArgs e)
        {
            if (_timer != null)
            {
                _timer.Cancel();
                _timer = null;

                lblMsg.Text += Environment.NewLine;
                lblMsg.Text += "任务取消了";
            }
        }
    }
}

<Page
    x:Class="XamlDemo.Thread.ThreadPool.PeriodicTimer"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Thread.ThreadPool"
    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="btnCreatePeriodic" Content="执行一个周期任务" Click="btnCreatePeriodic_Click_1" Margin="0 10 0 0" />

            <Button Name="btnCancelPeriodic" Content="取消任务" Click="btnCancelPeriodic_Click_1" Margin="0 10 0 0" />

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

/*
 * 通过 ThreadPoolTimer 实现周期执行（ThreadPoolTimer 在 Windows.System.Threading 命名空间下）
 * 
 * ThreadPoolTimer - 计时器
 *     ThreadPoolTimer CreatePeriodicTimer(TimerElapsedHandler handler, TimeSpan period, TimerDestroyedHandler destroyed) - 创建一个用于延迟执行的计时器
 *         handler - 每个周期时间点到达之后，所需要执行的方法
 *         period - 周期执行的间隔时间
 *         destroyed - 当 ThreadPoolTimer 完成了自身的使命后所执行的方法（比如计时器被取消了）
 *     Cancel() - 取消计时器
 *     Period - 间隔时间，只读
 */

using System;
using Windows.System.Threading;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace XamlDemo.Thread.ThreadPool
{
    public sealed partial class PeriodicTimer : Page
    {
        private ThreadPoolTimer _timer;
        private int _periodicTimerCount = 0;

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

        // 创建一个周期计时器
        private void btnCreatePeriodic_Click_1(object sender, RoutedEventArgs e)
        {
            _timer = ThreadPoolTimer.CreatePeriodicTimer(
                (timer) =>
                {
                    _periodicTimerCount++;

                    var ignored = Dispatcher.RunAsync(CoreDispatcherPriority.High,
                        () =>
                        {
                            lblMsg.Text = "任务执行次数：" + _periodicTimerCount.ToString();
                        });
                },
                // 第 1 次执行 handler 是在计时器被创建的 100 毫秒之后，然后每 100 毫秒执行一次 handler
                // 计时器会保证每 100 毫秒调用一次 handler，而不管上一次 handler 是否已执行完
                TimeSpan.FromMilliseconds(100), 
                (timer) => 
                {
                    var ignored = Dispatcher.RunAsync(CoreDispatcherPriority.High,
                        () =>
                        {
                            lblMsg.Text += Environment.NewLine;
                            lblMsg.Text += "ThreadPoolTimer 的使命结束了";
                        });
                });

            lblMsg.Text = "任务执行次数：0";
        }

        // 取消计时器
        private void btnCancelPeriodic_Click_1(object sender, RoutedEventArgs e)
        {
            if (_timer != null)
            {
                _timer.Cancel();
                _timer = null;
                _periodicTimerCount = 0;

                lblMsg.Text = "任务取消了";
            }
        }
    }
}

<Page
    x:Class="XamlDemo.Thread.ThreadPool.WorkItem"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.Thread.ThreadPool"
    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" />

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

            <Button Name="btnCreateWorkItem" Content="在线程池中找一个线程去执行指定的方法" Click="btnCreateWorkItem_Click_1" Margin="0 10 0 0" />
            <Button Name="btnCancelWorkItem" Content="取消任务" Click="btnCancelWorkItem_Click_1" Margin="0 10 0 0" />

            <Button Name="btnCreateWorkItemByAwait" Content="通过 async await 简化“在线程池中找一个线程去执行指定的方法”" Click="btnCreateWorkItemByAwait_Click_1" Margin="0 30 0 0" />

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

/*
 * 通过 ThreadPool 实现“在线程池中找一个线程去执行指定的方法”（ThreadPool 在 Windows.System.Threading 命名空间下）
 * 
 * ThreadPool - 线程池
 *     IAsyncAction RunAsync(WorkItemHandler handler, WorkItemPriority priority) - 在线程池中找一个线程去执行指定的方法，并指定其优先级
 *         handler - 需要调用的方法
 *         priority - 优先级（Windows.UI.Core.CoreDispatcherPriority 枚举：Low, Normal, High）
 *         
 *     
 * 注：关于 IAsyncAction 请参见 XamlDemo/Thread/Async 中的说明
 */

using System;
using System.Threading;
using Windows.Foundation;
using Windows.System.Threading;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace XamlDemo.Thread.ThreadPool
{
    public sealed partial class WorkItem : Page
    {
        private IAsyncAction _threadPoolWorkItem;
        private ManualResetEvent _sleep = new ManualResetEvent(false);

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

        // 在线程池中找一个线程去执行指定的方法，并指定其优先级
        private void btnCreateWorkItem_Click_1(object sender, RoutedEventArgs e)
        {
            _threadPoolWorkItem = Windows.System.Threading.ThreadPool.RunAsync(
                (threadPoolWorkItem) =>
                {
                    int percent = 0; // 用于模拟执行进度（0 - 100）
                    while (percent < 100)
                    {
                        // 当前线程 sleep 100 毫秒
                        _sleep.WaitOne(100);

                        // 如果 IAsyncAction 被取消了则退出此 handler 的执行
                        if (threadPoolWorkItem.Status == AsyncStatus.Canceled)
                            break;

                        percent++;

                        var ignored = Dispatcher.RunAsync(CoreDispatcherPriority.High,
                            () =>
                            {
                                lblProgress.Text = "进度：" + percent.ToString() + "%";
                            });
                    }
                },
                WorkItemPriority.High);

            // IAsyncAction 完成之后（比如任务完成了或者任务取消了）
            // 关于 IAsyncAction 的详细说明请参见 XamlDemo/Thread/Async
            _threadPoolWorkItem.Completed = new AsyncActionCompletedHandler(
                async (IAsyncAction threadPoolWorkItem, AsyncStatus status) =>
                {
                    await Dispatcher.RunAsync(CoreDispatcherPriority.High,
                        () =>
                        {
                            switch (status)
                            {
                                case AsyncStatus.Completed:
                                    lblMsg.Text = "任务完成了";
                                    break;
                                case AsyncStatus.Canceled:
                                    lblMsg.Text = "任务取消了";
                                    break;
                                case AsyncStatus.Started:
                                case AsyncStatus.Error:
                                    break;
                            }
                        });
                });

            lblProgress.Text = "进度：0%";
            lblMsg.Text = "任务开始了";
        }

        // 取消任务
        private void btnCancelWorkItem_Click_1(object sender, RoutedEventArgs e)
        {
            if (_threadPoolWorkItem != null)
            {
                _threadPoolWorkItem.Cancel();
                _threadPoolWorkItem = null;
            }
        }


        // 通过 async await 简化 ThreadPool.RunAsync() 的使用（关于 async 和 await 的详细说明请参见 XamlDemo/Thread/Async）
        private async void btnCreateWorkItemByAwait_Click_1(object sender, RoutedEventArgs e)
        {
            lblProgress.Text = "";
            lblMsg.Text = "";

            string result = "";

            await Windows.System.Threading.ThreadPool.RunAsync(
                delegate
                {
                    new ManualResetEvent(false).WaitOne(3000);
                    result = "在线程池中找一个线程去执行指定的逻辑，然后通过 await 返回 UI 线程";
                });

            lblMsg.Text = result;
        }
    }
}