WPF中的多进程(Threading)处理实例(二)

原文: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

FindPrimesInput

  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

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 = ; i < list.Length; i++)
             {
                 list[i] = fromNumber;
                 fromNumber += ;
             }

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

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

                 }

                 int iteration = list.Length / ;
                 if ((i % iteration == ) && (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 = ;
             for (int i = ; i < mark.Length; i++)
             {
                 if (mark[i] == )
                     primes += ;

             }

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

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

             return ret;

         }

     }

2.3BackgroundWorker XAML

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 = ;
         }

         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();
         }
     }