WPF 之Event

WPF中的Event

 

Routed Events 意指一个事件在一个相互关联的元素组成的树中传递，而非直接传递到一个特定的目标。

它可以在两个方向进行传递，Bubbling, tunneling

事件Routed的三种方式

1〉  Bubbling：事件由源头传递到元素树的最顶点

2〉  tunneling：事件由树的顶端传递的源头

3〉  direct：事件不在树中移动，表现方式类同标准的CLR事件

 

如何写Routed Event

示例：

Public static readonly RoutedEvent TapEvent =

EventManager.RegisterRoutedEvent(“Tap”,

RoutingStrategy.Bubble,

typeof(RoutedEventHandle),

typeof(MyButtonSimple)

);

// Provide CLR accessors for the event

Public event RoutedEventHandle Tap

{

       Add{AddHandler(TapEvent, value);}

       Remove{RemoveHandler(TapEvent, value);}

}

 

如何在Xaml关联事件

<Button Click=”blSetColor”>button</Button>

 

为什么要使用Routed Event

对于一组需要交互的控件，可以将父元素作为一个通用的事件监听者，然后使用同一个事件函数来处理交互。

示例如下

A grouped button set

XAML

<Border Height="50" Width="300" BorderBrush="Gray" BorderThickness="1">

  <StackPanel Background="LightGray" Orientation="Horizontal" Button.Click="CommonClickHandler">

    <Button Name="YesButton" Width="Auto" >Yes</Button>

    <Button Name="NoButton" Width="Auto" >No</Button>

    <Button Name="CancelButton" Width="Auto" >Cancel</Button>

  </StackPanel>

</Border>

 

C#

Private void CommonClickHandler(object sender, RoutedEventArgs e)

{

       FrameworkElement feSource = e.Source as FrameworkElement;

       Switch(feSource.Name)

       {

              Case “YesButton”:

                     // do something here

                     Break;

              Case “NoButton”

                     // do something

                     Break;

              Case “CancelButton”:

                     // do something

                     Break;

}

e.Handled = true;

}

自定义Event

示例如下：

 

//Invoke该事件

protected virtual void OnPipeValueChanged(double oldValue, double newValue)

        {

            RoutedPropertyChangedEventArgs<double> args = new RoutedPropertyChangedEventArgs<double>(oldValue, newValue);

            args.RoutedEvent = PipeControl.PipeValueChangedEvent;

            RaiseEvent(args);

        }

// 注册该事件

        public static readonly RoutedEvent PipeValueChangedEvent =

            EventManager.RegisterRoutedEvent("PipeValueChanged",

            RoutingStrategy.Bubble,

            typeof(RoutedPropertyChangedEventHandler<double>),

            typeof(PipeControl));