wpf 如何检测 TextBlock 的 Text 属性的变化？
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How to detect a change in the Text property of a TextBlock?
提问by Tono Nam
Is there any way to detect a change in the Text property of a TextBlock element using events?
有没有办法使用事件检测 TextBlock 元素的 Text 属性的变化？
(I'm trying to provide an animation for highlighting the TextBlocks whose Text property change within a DataGrid)
（我试图提供一个动画来突出显示在 DataGrid 中 Text 属性发生变化的 TextBlocks）
采纳答案by bioskope
As far as I can understand there isn't any textchanged event in TextBlock. Looking at your requirement, I feel that re-templating a textbox will also not be a viable solution. From my preliminary searching around, thisseems to be a possible solution.
据我所知，TextBlock 中没有任何 textchanged 事件。看看您的要求，我觉得重新模板化文本框也不是一个可行的解决方案。从我的初步搜索来看，这似乎是一个可能的解决方案。
<TextBlock x:Name="tbMessage" Text="{Binding Path=StatusBarText, NotifyOnTargetUpdated=True}">
<TextBlock.Triggers>
<EventTrigger RoutedEvent="Binding.TargetUpdated">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="Opacity" Duration="0:0:0″
To="1.0″ />
<DoubleAnimation Storyboard.TargetProperty="Opacity" Duration="0:0:2″
From="1.0″ To="0.0″ BeginTime="0:0:5″ />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</TextBlock.Triggers>
</TextBlock>
回答by Tono Nam
It's easier than that! Late answer, but much simpler.
这比这更容易！迟到的答案，但要简单得多。
// assume textBlock is your TextBlock
var dp = DependencyPropertyDescriptor.FromProperty(
TextBlock.TextProperty,
typeof(TextBlock));
dp.AddValueChanged(textBlock, (sender, args) =>
{
MessageBox.Show("text changed");
});
回答by Meirion Hughes
This is like the code from the link in bioskope's answer, but simplified. You need the TargetUpdatedevent and add NotifyOnTargetUpdated=Trueto the binding.
这类似于 bioskope 答案中链接中的代码，但已简化。您需要TargetUpdated事件并添加NotifyOnTargetUpdated=True到绑定中。
<TextBlock Text="{Binding YourTextProperty, NotifyOnTargetUpdated=True}"
TargetUpdated="YourTextEventHandler"/>
回答by Tal Segal
Bind the Text property to a DependencyProperty, which has an event trigger:
将 Text 属性绑定到一个 DependencyProperty，它有一个事件触发器：
public static string GetTextBoxText(DependencyObject obj)
{
return (string)obj.GetValue(TextBoxTextProperty);
}
public static void SetTextBoxText(DependencyObject obj, string value)
{
obj.SetValue(TextBoxTextProperty, value);
}
public static readonly DependencyProperty TextBoxTextProperty =
DependencyProperty.RegisterAttached(
"TextBoxText",
typeof(string),
typeof(TextBlockToolTipBehavior),
new FrameworkPropertyMetadata(string.Empty, TextBoxTextChangedCallback)
);
private static void TextBoxTextChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TextBlock textBlock = d as TextBlock;
HandleTextChange(textBlock);
}
In the XAML Bind to the TextBlock text Property:
在 XAML 绑定到 TextBlock 文本属性中：
<TextBlock
Text="{Binding SomeProperty, UpdateSourceTrigger=PropertyChanged}"
th:TextBlockBehavior.TextBoxText="{Binding Text,
RelativeSource={RelativeSource Self}}" />
回答by Nasheayahu
Here's something you can use I picked up from Jerry Nixon and Daren May at the Microsoft Virtual Academy "Developing Universal Windows Apps with C# and XAML" and the code that contains the DependencyObject logic is here "(W8.1-WP8.1) UNIVERSAL APP FOR MVA".
这是我从 Jerry Nixon 和 Daren May 在微软虚拟学院“使用 C# 和 XAML 开发通用 Windows 应用程序”以及包含 DependencyObject 逻辑的代码这里获取的一些你可以使用的东西“ (W8.1-WP8.1) UNIVERSAL适用于 MVA 的应用程序”。
namespace App1.Behaviors
{
// <summary>
/// Helper class that allows you to monitor a property corresponding to a dependency property
/// on some object for changes and have an event raised from
/// the instance of this helper that you can handle.
/// Usage: Construct an instance, passing in the object and the name of the normal .NET property that
/// wraps a DependencyProperty, then subscribe to the PropertyChanged event on this helper instance.
/// Your subscriber will be called whenever the source DependencyProperty changes.
/// </summary>
public class DependencyPropertyChangedHelper : DependencyObject
{
/// <summary>
/// Constructor for the helper.
/// </summary>
/// <param name="source">Source object that exposes the DependencyProperty you wish to monitor.</param>
/// <param name="propertyPath">The name of the property on that object that you want to monitor.</param>
public DependencyPropertyChangedHelper(DependencyObject source, string propertyPath)
{
// Set up a binding that flows changes from the source DependencyProperty through to a DP contained by this helper
Binding binding = new Binding
{
Source = source,
Path = new PropertyPath(propertyPath)
};
BindingOperations.SetBinding(this, HelperProperty, binding);
}
/// <summary>
/// Dependency property that is used to hook property change events when an internal binding causes its value to change.
/// This is only public because the DependencyProperty syntax requires it to be, do not use this property directly in your code.
/// </summary>
public static DependencyProperty HelperProperty =
DependencyProperty.Register("Helper", typeof(object), typeof(DependencyPropertyChangedHelper), new PropertyMetadata(null, OnPropertyChanged));
/// <summary>
/// Wrapper property for a helper DependencyProperty used by this class. Only public because the DependencyProperty syntax requires it.
/// DO NOT use this property directly.
/// </summary>
public object Helper
{
get { return (object)GetValue(HelperProperty); }
set { SetValue(HelperProperty, value); }
}
// When our dependency property gets set by the binding, trigger the property changed event that the user of this helper can subscribe to
private static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var helper = (DependencyPropertyChangedHelper)d;
helper.PropertyChanged(d, e);
}
/// <summary>
/// This event will be raised whenever the source object property changes, and carries along the before and after values
/// </summary>
public event EventHandler<DependencyPropertyChangedEventArgs> PropertyChanged = delegate { };
}
}
Usage XAML:
用法 XAML：
<TextBlock Grid.Row="0"
x:Name="WritingMenuTitle"
HorizontalAlignment="Left"
FontSize="32"
FontWeight="SemiBold"
Text="{Binding WritingMenu.Title}"
TextAlignment="Left"
TextWrapping="Wrap"/>
Usage xaml.cs:
用法 xaml.cs：
Behaviors.DependencyPropertyChangedHelper helper = new Behaviors.DependencyPropertyChangedHelper(this.WritingMenuTitle, Models.CommonNames.TextBlockText);
helper.PropertyChanged += viewModel.OnSenarioTextBlockTextChangedEvent;
Usage viewmodel.cs:
用法 viewmodel.cs：
public async void OnSenarioTextBlockTextChangedEvent(object sender, DependencyPropertyChangedEventArgs args)
{
StringBuilder sMsg = new StringBuilder();
try
{
Debug.WriteLine(String.Format(".....WritingMenuTitle : New ({0}), Old ({1})", args.NewValue, args.OldValue));
}
catch (Exception msg)
{
#region Exception
.....
#endregion
}
}
回答by BryanJ
Here is a similar example on MSDN using code-behind: http://msdn.microsoft.com/en-us/library/system.windows.data.binding.targetupdated.aspx
这是 MSDN 上使用代码隐藏的类似示例：http: //msdn.microsoft.com/en-us/library/system.windows.data.binding.targetupdated.aspx
