WPF中的多进程(Threading)处理实例(二)

    //错误的处理
        private void cmdBreakRules_Click(object sender, RoutedEventArgs e)
        {
            Thread thread = new Thread(UpdateTextWrong);
            thread.Start();
        }

        private void UpdateTextWrong()
        {
            txt.Text = "Here is some new text.";
        }

        //正确的处理
        private void cmdFollowRules_Click(object sender, RoutedEventArgs e)
        {
            Thread thread = new Thread(UpdateTextRight);
            thread.Start();
        }               

        private void UpdateTextRight()
        {
            this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
                (ThreadStart) delegate()
                {
                    //txt.Text = "Here is some new text.";
                    UpdateText();
                }
                );
        }

        private void UpdateText()
        {

            txt.Text = "这是更新后的文本。";
        }

说明：public DispatcherOperation BeginInvoke(DispatcherPriority priority, Delegate method);其中DispatcherPriority是从-1到10 的枚举值，10优先级最高。在UpdateTextRight方法中的一下代码段

            this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
                (ThreadStart)delegate()
                {
                    //txt.Text = "Here is some new text.";
                    UpdateText();
                }
                );

可以用一下代码来替换，以增加代码的可读性

private delegate void UpdateTextDelegate();
this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,new UpdateTextDelegate(UpdateText));

其实，这与上篇实例中应用的方法是相同的。


2.BackgroundWorker

2.1FindPrimesInput

 public class FindPrimesInput
    {        
        public int To
        { get; set; }

        public int From
        { get; set; }

        public FindPrimesInput(int from, int to)
        {
            To = to;
            From = from;
        }

    }

2.2 Worker

 public class Worker
    {
        public static int[] FindPrimes(int fromNumber, int toNumber)
        {
            return FindPrimes(fromNumber, toNumber, null);
        }

        public static int[] FindPrimes(int fromNumber, int toNumber, System.ComponentModel.BackgroundWorker backgroundWorker)
        {
            int[] list = new int[toNumber - fromNumber];

            // Create an array containing all integers between the two specified numbers.
            for (int i = 0; i < list.Length; i++)
            {
                list[i] = fromNumber;
                fromNumber += 1;
            }


            //find out the module for each item in list, divided by each d, where
            //d is < or == to sqrt(to)
            //if the remainder is 0, the nubmer is a composite, and thus
            //we mark its position with 0 in the marks array,
            //otherwise the number is a prime, and thus mark it with 1

            //Math.Floor 返回小于或等于指定双精度浮点数的最大整数。
            int maxDiv = (int)Math.Floor(Math.Sqrt(toNumber));

            int[] mark = new int[list.Length];

            for (int i = 0; i < list.Length; i++)
            {
                for (int j = 2; j <= maxDiv; j++)
                {

                    if ((list[i] != j) && (list[i] % j == 0))
                    {
                        mark[i] = 1;
                    }

                }

                int iteration = list.Length / 100;
                if ((i % iteration == 0) && (backgroundWorker != null))
                {
                    //BackgroundWorker.CancellationPending获取一个值，指示应用程序是否已请求取消后台操作。
                    if (backgroundWorker.CancellationPending)
                    {
                        // Return without doing any more work.
                        return null;                      
                    }

                    //BackgroundWorker.WorkerReportsProgress 获取或设置一个值，该值指示 System.ComponentModel.BackgroundWorker 能否报告进度更新。
                    if (backgroundWorker.WorkerReportsProgress)
                    {
                        //float progress = ((float)(i + 1)) / list.Length * 100;
                        //BackgroundWorker.ReportProgress 引发 System.ComponentModel.BackgroundWorker.ProgressChanged 事件。
                        backgroundWorker.ReportProgress(i / iteration);
                        //(int)Math.Round(progress));
                    }
                }

            }

            //create new array that contains only the primes, and return that array
            int primes = 0;
            for (int i = 0; i < mark.Length; i++)
            {
                if (mark[i] == 0)
                    primes += 1;

            }

            int[] ret = new int[primes];
            int curs = 0;
            for (int i = 0; i < mark.Length; i++)
            {
                if (mark[i] == 0)
                {
                    ret[curs] = list[i];
                    curs += 1;
                }
            }

            if (backgroundWorker != null && backgroundWorker.WorkerReportsProgress)
            {
                backgroundWorker.ReportProgress(100);
            }

            return ret;

        }

        
    }

2.3BackgroundWorker XAML

<Window x:Class="Multithreading.BackgroundWorkerTest"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Multithreading" Height="323.2" Width="305.6"
    xmlns:cm="clr-namespace:System.ComponentModel;assembly=System"
    >
    <Window.Resources>
        <cm:BackgroundWorker x:Key="backgroundWorker"
          WorkerReportsProgress="True" WorkerSupportsCancellation="True"
          DoWork="backgroundWorker_DoWork" ProgressChanged="backgroundWorker_ProgressChanged" 
          RunWorkerCompleted="backgroundWorker_RunWorkerCompleted"></cm:BackgroundWorker>
    </Window.Resources>

    <Grid Margin="5">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>


        <TextBlock Margin="5">From:</TextBlock>
        <TextBox Name="txtFrom" Grid.Column="1" Margin="5">1</TextBox>
        <TextBlock Grid.Row="1" Margin="5">To:</TextBlock>
        <TextBox Name="txtTo" Grid.Row="1" Grid.Column="1" Margin="5">500000</TextBox>

        <StackPanel Orientation="Horizontal"
              Grid.Row="2" Grid.Column="1">
            <Button Name="cmdFind"
              Margin="5" Padding="3"
              Click="cmdFind_Click">Find Primes</Button>
            <Button Name="cmdCancel"
              Margin="5" Padding="3" IsEnabled="False"
              Click="cmdCancel_Click">Cancel</Button>
        </StackPanel>

        <TextBlock Grid.Row="3" Margin="5">Results:</TextBlock>
        <ListBox Name="lstPrimes" Grid.Row="3" Grid.Column="1" 
               Margin="5"></ListBox>


        <ProgressBar Name="progressBar"
               Grid.Row="4" Grid.ColumnSpan="2"
               Margin="5" VerticalAlignment="Bottom" MinHeight="20" 
               Minimum="0" Maximum="100" Height="20"></ProgressBar>
    </Grid>
</Window>

2.4 CS code

 public partial class BackgroundWorkerTest : System.Windows.Window
    {
        public BackgroundWorkerTest()
        {
            InitializeComponent();
            //BackgroundWorker 在单独的线程上执行操作
            //Window.FindResource(object resourceKey)搜索具有指定密钥的资源，找不到则会引发异常
            backgroundWorker = ((BackgroundWorker)this.FindResource("backgroundWorker"));
        }

        private BackgroundWorker backgroundWorker;

        private void cmdFind_Click(object sender, RoutedEventArgs e)
        {
            // Disable the button and clear previous results.
            cmdFind.IsEnabled = false;
            cmdCancel.IsEnabled = true;
            lstPrimes.Items.Clear();            

            // Get the search range.
            int from, to;
            if (!Int32.TryParse(txtFrom.Text, out from))
            {
                MessageBox.Show("Invalid From value.");
                return;
            }
            if (!Int32.TryParse(txtTo.Text, out to))
            {
                MessageBox.Show("Invalid To value.");
                return;
            }

            // Start the search for primes on another thread.
            FindPrimesInput input = new FindPrimesInput(from, to);
            backgroundWorker.RunWorkerAsync(input);
        }

        private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            // Get the input values.
            FindPrimesInput input = (FindPrimesInput)e.Argument;

            // Start the search for primes and wait.
            int[] primes = Worker.FindPrimes(input.From, input.To, backgroundWorker);

            //BackgroundWorker.CancellationPending 获取一个值，指示应用程序是否已请求取消后台操作。
            if (backgroundWorker.CancellationPending)
            {
                e.Cancel = true;
                return;
            }

            // Return the result.
            e.Result = primes;
        }

        private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled)
            {
                MessageBox.Show("Search cancelled.");
            }
            else if (e.Error != null)
            {
                // An error was thrown by the DoWork event handler.
                MessageBox.Show(e.Error.Message, "An Error Occurred");
            }
            else
            {
                int[] primes = (int[])e.Result;
                foreach (int prime in primes)
                {
                    lstPrimes.Items.Add(prime);
                }                
            }
            cmdFind.IsEnabled = true;
            cmdCancel.IsEnabled = false;
            progressBar.Value = 0;
        }

        private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            //ProgressChangedEventArgs.ProgressPercentage 获取异步任务的进度百分比
            progressBar.Value = e.ProgressPercentage;
        }

        private void cmdCancel_Click(object sender, RoutedEventArgs e)
        {
            //BackgroundWorker.CancelAsync() 请求取消挂起后的操作
            backgroundWorker.CancelAsync();
        }
    }