我有一个很慢的WPF转换器(计算,在线提取等)。如何异步转换以便我的UI不会冻结?我找到了这个,但解决方案是将转换器代码放在属性 - http://social.msdn.microsoft.com/Forums/pl-PL/wpf/thread/50d288a2-eadc-4ed6-a9d3-6e249036cb71中 - 我宁愿不这样做。
以下是演示此问题的示例。这里的下拉列表将冻结,直到睡眠过去。
namespace testAsync
{
using System;
using System.Collections.Generic;
using System.Threading;
using System.Windows;
using System.Windows.Data;
using System.Windows.Threading;
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
MyNumbers = new Dictionary<string, int> { { "Uno", 1 }, { "Dos", 2 }, { "Tres", 3 } };
this.DataContext = this;
}
public Dictionary<string, int> MyNumbers
{
get { return (Dictionary<string, int>)GetValue(MyNumbersProperty); }
set { SetValue(MyNumbersProperty, value); }
}
public static readonly DependencyProperty MyNumbersProperty =
DependencyProperty.Register("MyNumbers", typeof(Dictionary<string, int>), typeof(MainWindow), new UIPropertyMetadata(null));
public string MyNumber
{
get { return (string)GetValue(MyNumberProperty); }
set { SetValue(MyNumberProperty, value); }
}
public static readonly DependencyProperty MyNumberProperty = DependencyProperty.Register(
"MyNumber", typeof(string), typeof(MainWindow), new UIPropertyMetadata("Uno"));
}
public class AsyncConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
object result = null;
if (values[0] is string && values[1] is IDictionary<string, int>)
{
DoAsync(
() =>
{
Thread.Sleep(2000); // Simulate long task
var number = (string)(values[0]);
var numbers = (IDictionary<string, int>)(values[1]);
result = numbers[number];
result = result.ToString();
});
}
return result;
}
private void DoAsync(Action action)
{
var frame = new DispatcherFrame();
new Thread((ThreadStart)(() =>
{
action();
frame.Continue = false;
})).Start();
Dispatcher.PushFrame(frame);
}
public object[] ConvertBack(object value, Type[] targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotSupportedException();
}
}
和XAML:
<Window x:Class="testAsync.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:testAsync"
Title="MainWindow" Height="200" Width="200">
<Window.Resources>
<local:AsyncConverter x:Key="asyncConverter"/>
</Window.Resources>
<DockPanel>
<ComboBox DockPanel.Dock="Top" SelectedItem="{Binding MyNumber, IsAsync=True}"
ItemsSource="{Binding MyNumbers.Keys, IsAsync=True}"/>
<TextBlock DataContext="{Binding IsAsync=True}"
FontSize="50" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock.Text>
<MultiBinding Converter="{StaticResource asyncConverter}">
<Binding Path="MyNumber" IsAsync="True"/>
<Binding Path="MyNumbers" IsAsync="True"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DockPanel>
</Window>
请注意,所有Bindings现在都是IsAsync =“True”,但这没有帮助。
组合框将卡住2000毫秒。
答案 0 :(得分:6)
我知道你说你不想从属性设置器中调用翻译,但我认为它比IValueConverter
/ IMultiValueConverter
更清晰。
最终,您想要从组合框中设置所选数字的值,并立即从中返回。您希望推迟更新显示/翻译的值,直到翻译过程完成。
我认为对数据进行建模更加清晰,使得转换后的值本身就是一个只能由异步进程更新的属性。
<ComboBox SelectedItem="{Binding SelectedNumber, Mode=OneWayToSource}"
ItemsSource="{Binding MyNumbers.Keys}"/>
<TextBlock Text="{Binding MyNumberValue}" />
public partial class MainWindow : Window, INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
MyNumbers = new Dictionary<string, int> { { "Uno", 1 }, { "Dos", 2 }, { "Tres", 3 } };
DataContext = this;
}
public IDictionary<string, int> MyNumbers { get; set; }
string _selectedNumber;
public string SelectedNumber
{
get { return _selectedNumber; }
set
{
_selectedNumber = value;
Notify("SelectedNumber");
UpdateMyNumberValue();
}
}
int _myNumberValue;
public int MyNumberValue
{
get { return _myNumberValue; }
set
{
_myNumberValue = value;
Notify("MyNumberValue");
}
}
void UpdateMyNumberValue()
{
var key = SelectedNumber;
if (key == null || !MyNumbers.ContainsKey(key)) return;
new Thread(() =>
{
Thread.Sleep(3000);
MyNumberValue = MyNumbers[key];
}).Start();
}
public event PropertyChangedEventHandler PropertyChanged;
void Notify(string property)
{
var handler = PropertyChanged;
if(handler != null) handler(this, new PropertyChangedEventArgs(property));
}
}
答案 1 :(得分:5)
您可以使用DispatcherFrame
,这是一个示例转换器:
public class AsyncConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
object result = null;
DoAsync(() =>
{
Thread.Sleep(2000); // Simulate long task
result = (int)value * 2; // Some sample conversion
});
return result;
}
private void DoAsync(Action action)
{
var frame = new DispatcherFrame();
new Thread((ThreadStart)(() =>
{
action();
frame.Continue = false;
})).Start();
Dispatcher.PushFrame(frame);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotSupportedException();
}
}
答案 2 :(得分:1)
在转换器中进行繁重的计算并不是一个好的设计 - 特别是如果你正在制作其他人应该使用的功能作为一个很好的例子。
我会使用你的ViewModel重写和使用MVVM作为类固醇的转换器,你可以用透明的方式完成所有这些事情 - 更容易编程,更容易理解的程序流,更容易理解代码。
然后你可以使用Prioritybindings:
http://msdn.microsoft.com/en-us/library/system.windows.data.prioritybinding.aspx
对于您的原始问题,我会在调用转换器时查看 - 如果绑定返回其值时,您可能无法让Async执行它的操作。我怀疑wpf等待属性返回然后调用转换器 - 在这种情况下,可能无法使转换器不能冻结gui。
您可以采取的方法:
答案 3 :(得分:0)
我建议查看BackgroundWorker
。它可以在后台线程上执行转换,然后在UI线程上引发已完成的事件。