DataStateBehavior for Enum而不是bool？串？

Question

在WPF中有一種簡單的方法將VisualState綁定到枚舉值嗎？有點像DataStateBehavior，但對於一個枚舉？

Answer 1

最好的方式就是繼續前進，實現一個行爲做到了這一點 -

public class EnumStateBehavior : Behavior<FrameworkElement> 
{ 
    public object EnumProperty 
    { 
     get { return (object)GetValue(EnumPropertyProperty); } 
     set { SetValue(EnumPropertyProperty, value); } 
    } 

    // Using a DependencyProperty as the backing store for EnumProperty. This enables animation, styling, binding, etc... 
    public static readonly DependencyProperty EnumPropertyProperty = 
     DependencyProperty.Register("EnumProperty", typeof(object), typeof(EnumStateBehavior), new UIPropertyMetadata(null, EnumPropertyChanged)); 

    static void EnumPropertyChanged(object sender, DependencyPropertyChangedEventArgs e) 
    { 
     if (e.NewValue == null) return; 

     EnumStateBehavior eb = sender as EnumStateBehavior; 

     VisualStateManager.GoToElementState(eb.AssociatedObject, e.NewValue.ToString(), true); 
    } 

} 

的使用非常簡單 - 使用方法如下：

<i:Interaction.Behaviors> 
     <local:EnumStateBehavior EnumProperty="{Binding MyEnumProperty}" /> 
</i:Interaction.Behaviors> 

Answer 2

有一個DataStateSwitchBehavior SL可以移植到WPF：Anyone have a DataStateSwitchBehavior for WPF4?

語法很簡單：

<is:DataStateSwitchBehavior Binding="{Binding Orientation}"> 
    <is:DataStateSwitchCase Value="Left" State="LeftState"/> 
    <is:DataStateSwitchCase Value="Right" State="RightState"/> 
    <is:DataStateSwitchCase Value="Down" State="DownState"/> 
    <is:DataStateSwitchCase Value="Up" State="UpState"/> 
<is:DataStateSwitchCase/> 

Answer 3

您可以在純xaml中使用每個可能的枚舉值使用DataTrigger，每個觸發器使用不同的狀態調用GoToStateAction。看下面的例子。欲瞭解更多詳情，請看 Enum driving a Visual State change via the ViewModel。

<i:Interaction.Triggers> 
     <ei:DataTrigger Binding="{Binding ConfirmedAnswerStatus}" Value="Unanswered"> 
      <ei:GoToStateAction StateName="UnansweredState" UseTransitions="False" /> 
     </ei:DataTrigger> 
     <ei:DataTrigger Binding="{Binding ConfirmedAnswerStatus}" Value="Correct"> 
      <ei:GoToStateAction StateName="CorrectlyAnsweredState" UseTransitions="True" /> 
     </ei:DataTrigger> 
     <ei:DataTrigger Binding="{Binding ConfirmedAnswerStatus}" Value="Incorrect"> 
      <ei:GoToStateAction StateName="IncorrectlyAnsweredState" UseTransitions="True" /> 
     </ei:DataTrigger> 
    </i:Interaction.Triggers> 

Answer 4

我遇到了上述EnumStateBehavior答案的問題。

的的PropertyChanged處理程序將首先觸發時的AssociatedObject爲空（因爲結合已經建立，但行爲尚未連接還）。此外，即使首次附加行爲，VisualState動畫的目標元素也可能不存在，因爲該行爲可能已經附加在其他子視覺樹之前。

的解決方案是使用Loaded事件相關聯的對象上，以確保結合的初始狀態被設置。

public class EnumStateBehavior : Behavior<FrameworkElement> 
{ 
    public static readonly DependencyProperty BindingProperty = 
     DependencyProperty.Register(nameof(Binding), typeof(object), typeof(EnumStateBehavior), new UIPropertyMetadata(null, BindingPropertyChanged)); 

    public object Binding 
    { 
     get { return (object)GetValue(BindingProperty); } 
     set { SetValue(BindingProperty, value); } 
    } 

    protected override void OnAttached() 
    { 
     base.OnAttached(); 

     this.AssociatedObject.Loaded += AssociatedObject_Loaded; 
    } 

    protected override void OnDetaching() 
    { 
     this.AssociatedObject.Loaded -= AssociatedObject_Loaded; 
     base.OnDetaching(); 
    } 

    private void AssociatedObject_Loaded(object sender, RoutedEventArgs e) 
    { 
     if (Binding != null) 
      GoToState(); 
    } 

    private void GoToState() 
    { 
     VisualStateManager.GoToElementState(this.AssociatedObject, Binding.ToString(), true); 
    } 

    private static void BindingPropertyChanged(object sender, DependencyPropertyChangedEventArgs e) 
    { 
     var eb = (EnumStateBehavior)sender; 

     if (e.NewValue == null || eb.AssociatedObject == null || !eb.AssociatedObject.IsLoaded) 
      return; 

     eb.GoToState(); 
    } 
}