WPF中如何创建自定义RoutedEvent实现灯光告警闪烁？

一、自定义RoutedEvent实现方式 #

如果坚持用路由事件触发，可以通过自定义控件封装告警相关的路由事件，步骤如下：

1. 自定义告警灯光控件
   继承自基础控件（比如Border），注册两个路由事件：AlarmTriggered（触发闪烁）和AlarmCleared（停止闪烁），并提供触发事件的方法：

public class AlarmLight : Border
{
    // 告警触发路由事件
    public static readonly RoutedEvent AlarmTriggeredEvent = EventManager.RegisterRoutedEvent(
        "AlarmTriggered", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(AlarmLight));

    public event RoutedEventHandler AlarmTriggered
    {
        add => AddHandler(AlarmTriggeredEvent, value);
        remove => RemoveHandler(AlarmTriggeredEvent, value);
    }

    public void RaiseAlarmTriggered()
    {
        RaiseEvent(new RoutedEventArgs(AlarmTriggeredEvent));
    }

    // 告警解除路由事件
    public static readonly RoutedEvent AlarmClearedEvent = EventManager.RegisterRoutedEvent(
        "AlarmCleared", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(AlarmLight));

    public event RoutedEventHandler AlarmCleared
    {
        add => AddHandler(AlarmClearedEvent, value);
        remove => RemoveHandler(AlarmClearedEvent, value);
    }

    public void RaiseAlarmCleared()
    {
        RaiseEvent(new RoutedEventArgs(AlarmClearedEvent));
    }
}

2. XAML中绑定事件与Storyboard
   在XAML里使用EventTrigger关联自定义路由事件，控制Storyboard的启停：

<local:AlarmLight x:Name="alarmLight" Background="Green">
    <local:AlarmLight.Triggers>
        <EventTrigger RoutedEvent="local:AlarmLight.AlarmTriggered">
            <BeginStoryboard>
                <Storyboard x:Name="FlashStoryboard">
                    <ColorAnimation Storyboard.TargetProperty="Background.Color" 
                                    From="Green" To="Red" Duration="0:0:0.5" 
                                    AutoReverse="True" RepeatBehavior="Forever"/>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
        <EventTrigger RoutedEvent="local:AlarmLight.AlarmCleared">
            <StopStoryboard BeginStoryboardName="FlashStoryboard"/>
            <ColorAnimation Storyboard.TargetProperty="Background.Color" 
                            To="Green" Duration="0:0:0.1"/>
        </EventTrigger>
    </local:AlarmLight.Triggers>
</local:AlarmLight>

3. 数据变化时触发事件
   在后台代码或ViewModel中监听数据变化，根据阈值判断调用对应的触发方法：

private void CheckAlarmStatus(double currentData, double threshold)
{
    if (currentData > threshold)
    {
        alarmLight.RaiseAlarmTriggered();
    }
    else
    {
        alarmLight.RaiseAlarmCleared();
    }
}

二、无需路由事件的更优方案（DataTrigger+MVVM） #

路由事件属于控件层面的交互逻辑，对于数据驱动的告警场景，更推荐用数据绑定+DataTrigger，完全贴合MVVM模式，代码更简洁耦合度更低：

1. ViewModel中定义告警状态属性
   实现INotifyPropertyChanged，通过数据变化自动更新告警状态：

public class MainViewModel : INotifyPropertyChanged
{
    private bool _isAlarmActive;
    public bool IsAlarmActive
    {
        get => _isAlarmActive;
        set
        {
            _isAlarmActive = value;
            OnPropertyChanged();
        }
    }

    private double _currentData;
    public double CurrentData
    {
        get => _currentData;
        set
        {
            _currentData = value;
            OnPropertyChanged();
            // 根据阈值切换告警状态（示例阈值为100）
            IsAlarmActive = _currentData > 100;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged([CallerMemberName] string propName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
    }
}

2. XAML中用DataTrigger控制动画
   直接绑定ViewModel的IsAlarmActive属性，通过DataTrigger的EnterActions和ExitActions控制Storyboard的启停：

<!-- 先在资源中声明ViewModel实例 -->
<Window.Resources>
    <local:MainViewModel x:Key="MainViewModel"/>
</Window.Resources>

<Border Background="Green" DataContext="{StaticResource MainViewModel}">
    <Border.Style>
        <Style TargetType="Border">
            <Style.Triggers>
                <DataTrigger Binding="{Binding IsAlarmActive}" Value="True">
                    <DataTrigger.EnterActions>
                        <BeginStoryboard>
                            <Storyboard x:Name="FlashStoryboard">
                                <ColorAnimation Storyboard.TargetProperty="Background.Color" 
                                                From="Green" To="Red" Duration="0:0:0.5" 
                                                AutoReverse="True" RepeatBehavior="Forever"/>
                            </Storyboard>
                        </BeginStoryboard>
                    </DataTrigger.EnterActions>
                    <DataTrigger.ExitActions>
                        <StopStoryboard BeginStoryboardName="FlashStoryboard"/>
                        <ColorAnimation Storyboard.TargetProperty="Background.Color" 
                                        To="Green" Duration="0:0:0.1"/>
                    </DataTrigger.ExitActions>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Border.Style>
</Border>

这个方案不需要自定义路由事件，完全由数据状态驱动UI变化，符合WPF的设计理念，后期维护和扩展也更方便。

内容的提问来源于stack exchange，提问作者CSTK6667