Silverlight雜談（1）- 跨線程訪問

 在Silverlight中，使用Thread,Timer,BackgrouWorker,ThreadPool可以實現多線程開發。但是隨之而來的問題是如何跨線程訪問資源呢？下面先以Timer計時器為例講解：

 示例

1、Timer.xaml

 
           1  
          < 
          UserControl  
          x:Class 
          ="ThreadDemo.Timer" 
          
 
           2  
              xmlns 
          ="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
          
 
           3  
              xmlns:x 
          ="http://schemas.microsoft.com/winfx/2006/xaml" 
          
 
           4  
              xmlns:d 
          ="http://schemas.microsoft.com/expression/blend/2008" 
          
 
           5  
              xmlns:mc 
          ="http://schemas.openxmlformats.org/markup-compatibility/2006" 
          
 
           6  
              mc:Ignorable 
          ="d" 
          
 
           7  
              d:DesignHeight 
          ="300" 
           d:DesignWidth 
          ="400" 
          > 
          
 
           8  
          
 
           9      
          < 
          Grid  
          x:Name 
          ="LayoutRoot" 
           Background 
          ="White" 
          > 
          
 
          10          
          < 
          ScrollViewer 
          > 
          
 
          11          
          < 
          StackPanel  
          x:Name 
          ="timerNum" 
          > 
          
 
          12              
          
 
          13          
          </ 
          StackPanel 
          > 
          
 
          14          
          </ 
          ScrollViewer 
          > 
          
 
          15      
          </ 
          Grid 
          > 
          
 
          16  
          </ 
          UserControl 
          > 
         

 Timer.cs

 
           1  
          using System; 
          
 
           2  
          using System.Collections.Generic; 
          
 
           3  
          using System.Linq; 
          
 
           4  
          using System.Net; 
          
 
           5  
          using System.Windows; 
          
 
           6  
          using System.Windows.Controls; 
          
 
           7  
          using System.Windows.Documents; 
          
 
           8  
          using System.Windows.Input; 
          
 
           9  
          using System.Windows.Media; 
          
 
          10  
          using System.Windows.Media.Animation; 
          
 
          11  
          using System.Windows.Shapes; 
          
 
          12  
          using System.Threading; 
          
 
          13  
          
 
          14  
          namespace ThreadDemo 
          
 
          15 { 
          
 
          16      
          public  
          partial  
          class Timer: UserControl 
          
 
          17     { 
          
 
          18          
          public Timer() 
          
 
          19         { 
          
 
          20             InitializeComponent(); 
          
 
          21              
          /// 
          實例化一個Timer時間器 
          
 
          22  
                      System.Threading.TimerTimer timer =  
          new System.Threading.TimerTimer( 
          new TimerCallback(TimerProc)); 
          
 
          23              
          /// 
          設定500毫秒后啟動，每隔1000毫秒執行一次 
          
 
          24  
                      timer.Change( 
          500,  
          1000); 
          
 
          25         } 
          
 
          26          
          int flagnum; 
          
 
          27          
          public  
          void TimerProc( 
          object state) 
          
 
          28         { 
          
 
          29                 flagnum++; 
          
 
          30                 TextBlock _temptext =  
          new TextBlock(); 
          
 
          31                 _temptext.Text = flagnum.ToString();  
         

                 timerNum.Children.Add(_temptext);
33         
34         }
35     }
36 }

 

F5運行程序，Visual Studio報錯，跨線程訪問無效。

 

 

這里使用TimerCallback委托指定希望Timer執行的方法，但是此方法不能在計時器線程上執行，所以這里就存在一個跨線程訪問的問題。下面調整下代碼，計時器線程將該工作委托給與該UI線程關聯的Dispatcher。使用Dispatcher.BeginInvoke.

 2、Timer.cs

 1  using System;
 2  using System.Collections.Generic;
 3  using System.Linq;
 4  using System.Net;
 5  using System.Windows;
 6  using System.Windows.Controls;
 7  using System.Windows.Documents;
 8  using System.Windows.Input;
 9  using System.Windows.Media;
10  using System.Windows.Media.Animation;
11  using System.Windows.Shapes;
12  using System.Threading;
13 
14  namespace ThreadDemo
15 {
16      public  partial  class Timer: UserControl
17     {
18          public Timer()
19         {
20             InitializeComponent();
21              /// 實例化一個Timer時間器
22              System.Threading.Timer timer =  new System.Threading.Timer( new TimerCallback(TimerProc));
23              ///設定500毫秒后啟動，每隔1000毫秒執行一次
24              timer.Change(500, 1000);
25         }
26          int flagnum;
27          public  void TimerProc( object state)
28         {
29              /// 在計時器的線程上使用Dispather.BeginInvoke，將計時器線程上的工作委托給UI線程關聯的Dispatcher
30               this.Dispatcher.BeginInvoke( delegate
31             {
32                 flagnum++;
33                 TextBlock _temptext =  new TextBlock();
34                 _temptext.Text = flagnum.ToString();
35                 timerNum.Children.Add(_temptext);
36             });
37            
38         
39         }
40     }  41 }

 F5運行成功

 

 接下來，我們再用AsyncOperation來實現跨線程訪問。

3、Thread.xaml

 1  < UserControl  x:Class ="ThreadDemo.Thread"
 2      xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3      xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml"
 4      xmlns:d ="http://schemas.microsoft.com/expression/blend/2008"
 5      xmlns:mc ="http://schemas.openxmlformats.org/markup-compatibility/2006"
 6      mc:Ignorable ="d"
 7      d:DesignHeight ="300"  d:DesignWidth ="400" >
 8     
 9      < Grid  x:Name ="LayoutRoot"  Background ="White" >
10          < ScrollViewer >
11              < StackPanel  x:Name ="timerNum" >
12 
13              </ StackPanel >
14          </ ScrollViewer >
15      </ Grid > 16  </ UserControl > 

 Thread.cs

 1  using System;
 2  using System.Collections.Generic;
 3  using System.Linq;
 4  using System.Net;
 5  using System.Windows;
 6  using System.Windows.Controls;
 7  using System.Windows.Documents;
 8  using System.Windows.Input;
 9  using System.Windows.Media;
10  using System.Windows.Media.Animation;
11  using System.Windows.Shapes;
12  using System.ComponentModel;
13 
14  namespace ThreadDemo
15 {
16      public  partial  class Thread : UserControl
17     {
18          private AsyncOperation async;
19         
20          public Thread()
21         {
22             InitializeComponent();
23             async = AsyncOperationManager.CreateOperation( null);
24             System.Threading.Thread thread =  new System.Threading.Thread(TimerProc);
25             thread.Start();
26         } 
27         
28          public  void TimerProc()
29         {
30            
31              async.Post(delegate
32             {
33             
34                 TextBlock _temptext =  new TextBlock();
35                 _temptext.Text = " 0 ";
36                 timerNum.Children.Add(_temptext);
37 
38             },  null);
39            
40         }
41 
42         
43     } 44 } 

ok.源碼下載