山东省建设节能协会网站/net的网站建设

当程序在进行一项耗时的工作时，加上一个UI显示当前的进度，这样可以避免让用户等到不耐烦，客户可能以为死机了，可能狂点鼠标，造成更差的效率问题。对于这个问题，解决方法有多种：

 

1，都在主线程中进行，将耗时任务分解成小块，主线程处理，同时更新GUI，MSDN中有个很好的例子 "A Single-Threaded Application with a Long-Running Calculation"；

 

2，工作线程为非GUI线程，负责处理耗时工作，主线程更新GUI。这种方法只有一个GUI线程，对多线程编程，这个是通常的选择；

 

3，主线程，工作线程都是UI线程，主线程处理耗时工作，工作线程负责处理UI更新提示。某些情况下，不得不这么做。这里详细介绍一个实现。

 

namespace Program
{
public class WaitPromptArgs
{
public bool ShowInCenterOfScreen { get; set; }
public double Left { get; set; }
public double Top { get; set; }

public string Status { get; set; }
}

public class WaitPrompt
{
private bool working = false;

private readonly Window ParentWnd = null;
public WaitPrompt(Window owner)
{
ParentWnd = owner;
}

private readonly ManualResetEvent BeginComplete = new ManualResetEvent(false);
public void BeginWait()
{
try
{
BeginComplete.Reset();
working = true;

// calc startup position
WaitPromptArgs args = new WaitPromptArgs();
if (ParentWnd == null)
{
args.ShowInCenterOfScreen = true;
}
else
{
// change cursor to hourglass
ParentWnd.Cursor = Cursors.Wait;

args.ShowInCenterOfScreen = false;
args.Left = ParentWnd.Left + 4;
args.Top = ParentWnd.Top + 32;
}
args.Status = string.Empty;

// start a new thread
t = new Thread(new ParameterizedThreadStart(OnThreadStart));
t.SetApartmentState(ApartmentState.STA);
t.IsBackground = true;
t.Start(args);

BeginComplete.WaitOne(); // wait untill process start complete
}
catch (Exception e)
{
throw new Exception("wait prompt window", e);
}
}

private Thread t = null;
private Dispatcher theDispatcher = null;
private DispatcherFrame theFrame = null;
private WaitingWnd w = null;

private void OnThreadStart(object obj)
{
try
{
WaitPromptArgs args = obj as WaitPromptArgs;
w = new WaitingWnd();
if (args.ShowInCenterOfScreen)
{
w.WindowStartupLocation = WindowStartupLocation.CenterScreen;
}
else
{
w.WindowStartupLocation = WindowStartupLocation.Manual;
w.Left = args.Left;
w.Top = args.Top;
}
w.Show();

theFrame = new DispatcherFrame();
theDispatcher = Dispatcher.CurrentDispatcher;

BeginComplete.Set(); // start complete, notify other threads

theDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(UpdateDescription), args.Status);
Dispatcher.PushFrame(theFrame);

w.Close();
w = null;
}
catch (ThreadAbortException)
{
Thread.ResetAbort();
}
finally
{
CleanUp();
}
}

// you can NOT directly set this string, because the other thread holds the window
// so, have to delegate by the other thread dispatcher object
public void UpdateHint(string hint)
{
if (working)
{
// w.Description = hint;
theDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(UpdateDescription), hint);
}
}
private object UpdateDescription(object des)
{
w.Description = des as string;
return null;
}

public void EndWait()
{
try
{
theDispatcher.BeginInvoke(DispatcherPriority.Normal, new DispatcherOperationCallback(ExitFrames), theFrame);
}
catch (Exception e)
{
throw new Exception("wait prompt window", e);
}
finally
{
if (ParentWnd != null)
ParentWnd.Cursor = Cursors.Arrow;

working = false;
}
}
private object ExitFrames(object f)
{
((DispatcherFrame)f).Continue = false;
return null;
}
private void CleanUp()
{
try
{
if (w != null)
w.Close();

 

Debug.Assert(t != null && theDispatcher != null && theFrame != null);

t = null;
theDispatcher = null;
theFrame = null;
w = null;
}
catch (Exception e)
{
throw new Exception("wait prompt window", e);
}
}
}
}

 

<Window
x:Class="Program.WaitingWnd"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Please wait ..." Height="100" Width="380" ResizeMode="NoResize"
Background="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"
WindowStyle="ToolWindow" WindowStartupLocation="Manual"
>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="32"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock x:Name="_description" HorizontalAlignment="Left" VerticalAlignment="Center" Text="TextBlock" TextWrapping="Wrap" Margin="10,0,0,0"/>
<ProgressBar HorizontalAlignment="Stretch" VerticalAlignment="Center" Width="Auto" Height="15" Grid.Row="1" Margin="10,0,10,0" IsIndeterminate="True"/>
</Grid>
</Window>

 

namespace Program
{
/// <summary>
/// Interaction logic for WaitingWnd.xaml
/// </summary>
public partial class WaitingWnd : Window
{
public string Description { set { _description.Text = value; } }

public WaitingWnd()
{
InitializeComponent();
}
}
}

 

public partial class Window1 : Window
{
readonly WaitPrompt wp = null;
public Window1()
{
InitializeComponent();

wp = new WaitPrompt(this);
}


private void Begin_Click(object sender, RoutedEventArgs e)
{
wp.BeginWait();
wp.UpdateHint("hello world!");
}

private void Send_Click(object sender, RoutedEventArgs e)
{
wp.UpdateHint(theWords.Text);
}

private void End_Click(object sender, RoutedEventArgs e)
{
wp.EndWait();
}
}