WPF 中是否有一种简单的方法可以将 VisualStates 绑定到枚举值?有点像 DataStateBehavior,但对于枚举?
问问题
1935 次
4 回答
4
最好的方法是继续执行一个 Behavior 来做到这一点 -
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);
}
}
用法非常简单——使用如下:
<i:Interaction.Behaviors>
<local:EnumStateBehavior EnumProperty="{Binding MyEnumProperty}" />
</i:Interaction.Behaviors>
于 2011-02-26T00:22:42.377 回答
3
您可以在纯 xaml 中执行此操作,方法是使用每个可能的枚举值的 DataTrigger,每个触发器调用具有不同状态的 GoToStateAction。请参见下面的示例。有关更多详细信息,请查看 Enum 通过 ViewModel 驱动视觉状态更改。
<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>
于 2012-02-09T18:46:35.120 回答
1
SL 中有一个 DataStateSwitchBehavior 可以移植到 WPF:有人有 WPF4 的 DataStateSwitchBehavior 吗?
语法非常简单:
<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/>
于 2011-03-25T16:49:02.957 回答
0
我对上述 EnumStateBehavior 答案有疑问。
当 AssociatedObject 为 null 时,PropertyChanged 处理程序将首先触发(因为已设置绑定但尚未附加 Behavior)。此外,即使第一次附加行为,VisualState 动画的目标元素可能还不存在,因为该行为可能已在其他子视觉树之前附加。
解决方案是在关联对象上使用 Loaded 事件来确保设置绑定的初始状态。
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();
}
}
于 2016-12-02T22:58:39.330 回答