WPF Behavior

前提條件

• 下載Wpf Behavior庫 - Microsoft.Xaml.Behaviors.Wpf
  tip: b 是我對應Behavior的代號

  xmlns:b="http://schemas.microsoft.com/xaml/behaviors"
  

介紹

<b:Interaction.Triggers>
    <b:EventTrigger EventName="Loaded">
        <b:CallMethodAction MethodName="Method" TargetObject="{Binding}" />
    </b:EventTrigger>
</b:Interaction.Triggers>

這是一個常見的用法，Iteraction類中定義了兩個依賴屬性

• Triggers
• Behaviors

源碼

private static readonly DependencyProperty TriggersProperty = DependencyProperty.RegisterAttached("ShadowTriggers",typeof(TriggerCollection),typeof(Interaction),new FrameworkPropertyMetadata(new PropertyChangedCallback(OnTriggersChanged)));


private static readonly DependencyProperty BehaviorsProperty = DependencyProperty.RegisterAttached("ShadowBehaviors", typeof(BehaviorCollection),typeof(Interaction),new FrameworkPropertyMetadata(new PropertyChangedCallback(OnBehaviorsChanged)));

Trigger

Trigger的類型為TriggerCollection,可以為其添加多個TriggerBase，Behavior包為我們提供了多種Trigger,一下介紹一些常用的Trigger

EventTrigger

事件觸發，EventName為事件名稱，SourceObject為觸發事件的對象，默認為附加的依賴屬性

<b:EventTrigger EventName="Click" SourceObject="{Binding ElementName=button}"/>

DataTrigger

數據觸發，Binding為綁定數據，Value為綁定數據中的值，當Binding的值等于Value時觸發

<b:DataTrigger  Binding="{Binding ElementName=checkBox, Path=IsChecked}" Value="true" />

PropertyChangedTrigger

屬性改變觸發，Binding為綁定數據，當Binding的值改變時觸發

<b:PropertyChangedTrigger Binding="{Binding ElementName=checkBox, Path=IsChecked}"/>

Action

CallMethodAction

調用方法，MethodName為方法名稱，TargetObject為方法所屬的對象，默認為附加的依賴屬性

<b:CallMethodAction MethodName="Method" TargetObject="{Binding Object}" />

InvokeCommandAction

<b:InvokeCommandAction Command="{Binding TestActiveCommand}" />

ControlStoryboardAction

ControlStoryboardAction表示將在執行時更改指定Storyboard狀態的操作。使用此行為可以使用ControlStoryboard屬性觸發和控制指定的Storyboard

ControlStoryboardOption 枚舉

<UserControl.Resources>
  <Storyboard x:Key="StoryboardSample" AutoReverse="True" RepeatBehavior="Forever">
    <DoubleAnimation Duration="0:0:2.2" To="0.35"
      Storyboard.TargetProperty="(UIElement.RenderTransform).(ScaleTransform.ScaleX)"
      Storyboard.TargetName="StoryboardRectangle" d:IsOptimized="True"/>
    <DoubleAnimation Duration="0:0:2.2" To="0.35"
      Storyboard.TargetProperty="(UIElement.RenderTransform).(ScaleTransform.ScaleY)"
      Storyboard.TargetName="StoryboardRectangle" d:IsOptimized="True"/>
  </Storyboard>
 </UserControl.Resources>

<Rectangle x:Name="StoryboardRectangle" />
<Button x:Name="button">
  <Behaviors:Interaction.Triggers>
    <Behaviors:EventTrigger EventName="Click">
      <Behaviors:ControlStoryboardAction Storyboard="{StaticResource StoryboardSample}" ControlStoryboardOption="TogglePlayPause"/>
    </Behaviors:EventTrigger>
  </Behaviors:Interaction.Triggers>
</Button>

GoToStateAction

GoToStateAction表示在觸發時會將FrameworkElement（即Button）轉換為指定的VisualState的操作。此行為會將TargetObject或TargetName指定的元素更改為可視狀態StateName。除非UseTrantions設置為false，否則當前狀態和新狀態之間的任何轉換都將播放。

<Button x:Name="sampleStateButton">
  <Button.Resources>
    <Style TargetType="Button" >
      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate TargetType="Button">
            <Grid x:Name="BaseGrid">
              <VisualStateManager.VisualStateGroups>
                <VisualStateGroup>
                  <VisualState x:Name="Normal">
                    <Storyboard>
                      <DoubleAnimation Storyboard.TargetName="BaseGrid" Storyboard.TargetProperty="Opacity" To="1.0" From="1.0"/>
                    </Storyboard>
                  </VisualState>
                  <VisualState x:Name="Disabled">
                    <Storyboard>
                      <DoubleAnimation Storyboard.TargetName="BaseGrid" Storyboard.TargetProperty="Opacity" To="0.25" From="1.0"/>
                    </Storyboard>
                  </VisualState>
                </VisualStateGroup>
              </VisualStateManager.VisualStateGroups>
            </Grid>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>
  </Button.Resources>
</Button>

<CheckBox x:Name="checkBox">
  <Behaviors:Interaction.Triggers>
    <Behaviors:DataTrigger Binding="{Binding IsChecked, ElementName=checkBox}" Value="False">
      <Behaviors:GoToStateAction StateName="Normal" TargetObject="{Binding ElementName=sampleStateButton}"/>
    </Behaviors:DataTrigger>
    <Behaviors:DataTrigger Binding="{Binding IsChecked, ElementName=checkBox}" Value="True">
      <Behaviors:GoToStateAction StateName="Disabled" TargetObject="{Binding ElementName=sampleStateButton}"/>
    </Behaviors:DataTrigger>
  </Behaviors:Interaction.Triggers>
</CheckBox>

Behavior

Behavior是一個行為，當事件發生時，會觸發Behavior中的行為

ConditionBehavior

條件行為，ConditionalExpression為條件表達式，當條件表達式為真時，觸發Behavior中的行為

<b:Interaction.Triggers>
    <b:EventTrigger EventName="Click" SourceObject="{Binding ElementName=Button}">
        <b:Interaction.Behaviors>
            <b:ConditionBehavior>
                <b:ConditionalExpression>
                    <b:ComparisonCondition LeftOperand="{Binding Path=Items.Count, ElementName=TabControl}" RightOperand="0" />
                </b:ConditionalExpression>
            </b:ConditionBehavior>
        </b:Interaction.Behaviors>
        <b:ChangePropertyAction/>
    </b:EventTrigger>
</b:Interaction.Triggers>

DataStateBehavior

當行為綁定到的數據等于某個值時，DataStateBeact執行操作。每當更新關聯的綁定時，此行為都會檢查綁定結果是否等于某個值。如果兩個值相等，則轉換為TrueState。否則，它會轉換為FalseState。

<Button x:Name="sampleStateButton">
  <Button.Resources>
    <Style TargetType="Button" >
      <Setter Property="Template">
        <Setter.Value>
           <ControlTemplate TargetType="Button">
           <Grid x:Name="BaseGrid" Background="DeepPink">
             <VisualStateManager.VisualStateGroups>
               <VisualStateGroup>
                 <VisualState x:Name="Normal">
                   <Storyboard>
                     <ColorAnimation Storyboard.TargetName="BaseGrid" Storyboard.TargetProperty="(Background).(SolidColorBrush.Color)" To="DarkBlue" From="DeepPink" />
                   </Storyboard>
                  </VisualState>
                  <VisualState x:Name="Blue">
                    <Storyboard>
                      <ColorAnimation Storyboard.TargetName="BaseGrid" Storyboard.TargetProperty="(Background).(SolidColorBrush.Color)" To="DeepPink" From="DarkBlue" Duration="Forever" />
                    </Storyboard>
                  </VisualState>
                </VisualStateGroup>
              </VisualStateManager.VisualStateGroups>
              <Behaviors:Interaction.Behaviors>
                <Behaviors:DataStateBehavior Binding="{Binding Text, ElementName=MyText}" Value="" TrueState="Normal" FalseState="Blue" />
              </Behaviors:Interaction.Behaviors>
            </Grid>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>
  </Button.Resources>
</Button>