wpf - 如何检测 TextBlock 的 Text 属性的变化？

Question

有没有办法使用事件检测 TextBlock 元素的 Text 属性的变化？

（我正在尝试提供一个动画来突出显示其 Text 属性在 DataGrid 中发生变化的 TextBlocks）

Answer 1

这比那更容易！迟到的答案，但更简单。

// assume textBlock is your TextBlock
var dp = DependencyPropertyDescriptor.FromProperty(
             TextBlock.TextProperty,
             typeof(TextBlock));
dp.AddValueChanged(textBlock, (sender, args) =>
{
    MessageBox.Show("text changed");
});

Answer 2

这就像 bioskope 答案中链接中的代码，但简化了。您需要该TargetUpdated事件并添加NotifyOnTargetUpdated=True到绑定中。

<TextBlock Text="{Binding YourTextProperty, NotifyOnTargetUpdated=True}" 
           TargetUpdated="YourTextEventHandler"/>

Answer 3

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。根据我的初步搜索，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>

Answer 4

将 Text 属性绑定到具有事件触发器的 DependencyProperty：

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);
}

在 XAML 中绑定到 TextBlock 文本属性：

<TextBlock  
 Text="{Binding SomeProperty, UpdateSourceTrigger=PropertyChanged}"  
     th:TextBlockBehavior.TextBoxText="{Binding Text, 
     RelativeSource={RelativeSource Self}}" />

Answer 5

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

Answer 6

这是你可以使用的东西，我从微软虚拟学院的 Jerry Nixon 和 Daren May “使用 C# 和 XAML 开发通用 Windows 应用程序”和包含 DependencyObject 逻辑的代码在这里“ （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 { };
}
}

使用 XAML：

<TextBlock Grid.Row="0"
       x:Name="WritingMenuTitle"
       HorizontalAlignment="Left"
       FontSize="32"
       FontWeight="SemiBold"
       Text="{Binding WritingMenu.Title}"
       TextAlignment="Left"
       TextWrapping="Wrap"/>

用法 xaml.cs：

Behaviors.DependencyPropertyChangedHelper helper = new Behaviors.DependencyPropertyChangedHelper(this.WritingMenuTitle, Models.CommonNames.TextBlockText);
helper.PropertyChanged += viewModel.OnSenarioTextBlockTextChangedEvent;

使用 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
}
}