Question

我有一个WPF数据触发器，当值为true时设置为触发。

我希望每次将此值设置为true时触发此触发器，即使之前为真。不幸的是，如果值从true变为false或反之亦然，似乎只会触发。我的基础数据模型正在触发INotifyPropertyChanged的PropertyChanged事件，即使该值连续两次设置为true，但触发器似乎没有选择它。

无论绑定值是否发生变化，无论如何都要使触发器运行？

你们中的一些人已经要求提供代码了。有趣的是，每次都会调用转换器。问题更具体到运行动画。

更新如果我更改我的代码以将值重置为false然后再次返回true，则会触发动画。显然这并不理想，并且不会使代码很好阅读。我希望有更好的方法来做到这一点。

非常感谢任何帮助。

WPF代码

<Grid>
    <Grid.Resources>            
        <Storyboard x:Key="AnimateCellBlue">
            <ColorAnimation Storyboard.TargetProperty="Background.Color" From="Transparent" To="Blue" Duration="0:0:0.1" AutoReverse="True" RepeatBehavior="1x" />
        </Storyboard>
    </Grid.Resources>
    <TextBox Name="txtBox" Text="{Binding DataContext.DisplayText, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}">           
        <TextBox.Style>
            <Style TargetType="TextBox">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding DataContext.IsTrue, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}" Value="True">
                        <DataTrigger.EnterActions>                                                        
                            <BeginStoryboard Name="BidSizeUpStoryB" Storyboard="{StaticResource AnimateCellBlue}" />
                        </DataTrigger.EnterActions>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBox.Style>
    </TextBox>
</Grid>

代码背后： -

public partial class MainWindow : Window
{
    private DataItem _dataItem;
    private DispatcherTimer _dispatcherTimer;

    public MainWindow()
    {
        InitializeComponent();

        _dataItem = new DataItem();
        _dataItem.DisplayText = "Testing";
        _dataItem.IsTrue = true;

        this.DataContext = _dataItem;

        _dispatcherTimer = new DispatcherTimer(TimeSpan.FromSeconds(1), DispatcherPriority.Normal, TimerCallbackHandler, Dispatcher);

    }

    private void TimerCallbackHandler(object s, EventArgs args)
    {
        Console.WriteLine("In Timer");
        _dataItem.IsTrue = true;
        _dataItem.DisplayText = "Timer " + DateTime.Now.Ticks;
    }
}

的DataItem： -

public class DataItem : INotifyPropertyChanged
{
    private bool _isTrue;
    private string _displayText;

    public bool IsTrue
    {
        get { return _isTrue; }
        set
        {
            _isTrue = value;
            NotifyPropertyChanged("IsTrue");
        }
    }

    public string DisplayText
    {
        get
        {
            return _displayText;
        }
        set 
        { 
            _displayText = value;
            NotifyPropertyChanged("DisplayText");
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion

    private void NotifyPropertyChanged(string info)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(info));
    }
}

Answer 1

无论设定的值如何，触发器都将触发。每当为带有触发器的绑定属性引发PropertyChanged事件时，将触发该触发器。这是我验证过的样本 -

<TextBox>
   <TextBox.Style>
       <Style TargetType="TextBox">
          <Style.Triggers>
             <DataTrigger Binding="{Binding DataContext.IsTrue, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window},
                                                        Converter={StaticResource MyConverter}}" Value="True">
                  <Setter Property="Background" Value="Red"/>
             </DataTrigger>
          </Style.Triggers>
       </Style>
   </TextBox.Style>
</TextBox>

我把断点放在我的转换器上，只要我为属性IsTrue引发PropertyChanged事件就会调用它。您的代码中还有其他一些问题。你能否在你面临这个问题的地方展示你的代码？

Answer 2

更新：似乎我的第一个答案取决于我的ValueConverters。所以，我做了一些研究，发现了ConditionalBehavior和PropertyChangedTrigger

这是我测试过的一个。

<UserControl
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" 
             xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions" 
             x:Class="WpfControlLibrary1.UserControl1" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Triggers>
        <EventTrigger RoutedEvent="FrameworkElement.Loaded"/>
    </UserControl.Triggers>
    <Grid>
        <i:Interaction.Triggers>
            <!--Use multiple PropertyChangedTriggers to handle multiple conditions-->
            <!--True State-->
            <ei:PropertyChangedTrigger Binding="{Binding DataContext.IsTrue, 
                    RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}" >
                <i:Interaction.Behaviors>
                    <!--This is just a humble demonstration of Conditional Behavior, it's has so much potential that you can replicate  complex if conditions-->
                    <ei:ConditionBehavior>
                        <ei:ConditionalExpression ForwardChaining="And">
                            <ei:ComparisonCondition Operator="Equal"
                                LeftOperand="{Binding DataContext.IsTrue, RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}"
                                RightOperand="True"
                            />
                        </ei:ConditionalExpression>
                    </ei:ConditionBehavior>
                </i:Interaction.Behaviors>
                <!--I'm not sure why, but I needed to apply the default state first so that the true state plays it's storyboard.-->
                <!--If you don't do this, this behaves like a data trigger.-->
                <ei:GoToStateAction StateName="DefaultState"/>
                <ei:GoToStateAction StateName="TrueState"/>
            </ei:PropertyChangedTrigger>

            <!--False state-->
            <ei:PropertyChangedTrigger Binding="{Binding DataContext.IsTrue, 
                    RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}" >
                <i:Interaction.Behaviors>
                    <ei:ConditionBehavior>
                        <ei:ConditionalExpression ForwardChaining="And">
                            <ei:ComparisonCondition Operator="Equal"
                                LeftOperand="{Binding DataContext.IsTrue, RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}"
                                RightOperand="False"
                            />
                        </ei:ConditionalExpression>
                    </ei:ConditionBehavior>
                </i:Interaction.Behaviors>
                <ei:GoToStateAction StateName="DefaultState"/>
            </ei:PropertyChangedTrigger>
        </i:Interaction.Triggers>
        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="VisualStateGroup">
                <VisualState x:Name="DefaultState"/>
                <VisualState x:Name="TrueState">
                    <Storyboard Storyboard.TargetName="txtBox" >
                        <ColorAnimation Storyboard.TargetProperty="Background.Color" From="Transparent" To="Blue" Duration="0:0:0.1" AutoReverse="True" RepeatBehavior="1x" />
                    </Storyboard>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
        <TextBox x:Name="txtBox" Text="{Binding DataContext.DisplayText, RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}"/>
    </Grid>
</UserControl>

您可以使用Visual State Groups进行此操作。更重要的是，行为属性和价值都可以是数据绑定！

我在混合中很快就做到了这一点并没有进行测试。这与我的解决方案类似。

<UserControl
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" 
             xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions" 
             x:Class="WpfControlLibrary1.UserControl1" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <i:Interaction.Behaviors>
            <ei:DataStateBehavior Binding="{Binding DataContext.IsTrue, 
                    RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}" 
                Value="True" 
                TrueState="TrueState"/>
        </i:Interaction.Behaviors>
        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="VisualStateGroup">
                <VisualState x:Name="DefaultState"/>
                <VisualState x:Name="TrueState">
                    <Storyboard Storyboard.TargetName="txtBox" >
                        <ColorAnimation Storyboard.TargetProperty="Background.Color" From="Transparent" To="Blue" Duration="0:0:0.1" AutoReverse="True" RepeatBehavior="1x" />
                    </Storyboard>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
        <TextBox x:Name="txtBox" Text="{Binding DataContext.DisplayText, RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}"/>
    </Grid>
</UserControl>

如果值保持不变，WPF DataTrigger不会触发

2 个答案: