如何将一个行为附加到某个元素上呢？我们可以通过自定义一个Behavior！
我们首先看一下IAttachedObject接口，Behavior默认继承之这个接口
// 摘要: // 供可以附加到另一个对象的对象使用的接口。
public interface IAttachedObject
{ // 摘要: // 获得关联的对象。 //
// 备注: // 代表此实例附加到的对象。
DependencyObject AssociatedObject { get; } // 摘要: // 附加到指定的对象。 //
// 参数: // dependencyObject: // 要附加到的对象。
void Attach(DependencyObject dependencyObject); //
// 摘要: // 将此实例与其关联的对象分离。
void Detach();
}
下面我们自定义一个Behavior附加到ListBox元素上：
public class SelectedItemFillBehavior : Behavior
{ // Using a DependencyProperty as the backing store for DefaultHeight. This enables animation, styling, binding, etc…
public static readonly DependencyProperty DefaultHeightProperty = DependencyProperty.Register(“DefaultHeight”, typeof(double), typeof(SelectedItemFillBehavior), new UIPropertyMetadata(30.0)); // Using a DependencyProperty as the backing store for AnimationDuration. This enables animation, styling, binding, etc…
public static readonly DependencyProperty AnimationDurationProperty = DependencyProperty.Register(“AnimationDuration”, typeof(int), typeof(SelectedItemFillBehavior), new UIPropertyMetadata(300)); public double DefaultHeight
{ get { return (double)GetValue(DefaultHeightProperty); } set { SetValue(DefaultHeightProperty, value); }
} public int AnimationDuration
{ get { return (int)GetValue(AnimationDurationProperty); } set { SetValue(AnimationDurationProperty, value); }
} protected override void OnAttached()
{ base.OnAttached(); //附加行为后需要处理的事件
AssociatedObject.SelectionChanged += new SelectionChangedEventHandler(OnAssociatedObjectSelectionChanged);
} protected override void OnDetaching()
{ base.OnDetaching(); //解除的事件
AssociatedObject.SelectionChanged -= new SelectionChangedEventHandler(OnAssociatedObjectSelectionChanged);
} private void OnAssociatedObjectSelectionChanged(object sender, SelectionChangedEventArgs e)
{ double selectedItemFinalHeight = AssociatedObject.ActualHeight;
Storyboard storyBoard \= new Storyboard(); for (int i = 0; i < AssociatedObject.Items.Count; i++)
{
ListBoxItem item \= AssociatedObject.ItemContainerGenerator.ContainerFromIndex(i) as ListBoxItem; if (!item.IsSelected)
{
selectedItemFinalHeight \-= DefaultHeight;
DoubleAnimation heightAnimation \= new DoubleAnimation()
{
To \= DefaultHeight,
Duration \= new Duration(new TimeSpan(0, 0, 0, 0, AnimationDuration))
};
Storyboard.SetTarget(heightAnimation, item);
Storyboard.SetTargetProperty(heightAnimation, new PropertyPath(FrameworkElement.HeightProperty));
storyBoard.Children.Add(heightAnimation);
}
}
selectedItemFinalHeight \-= 4; if (AssociatedObject.SelectedIndex >= 0)
{
ListBoxItem selectedItem \= AssociatedObject.ItemContainerGenerator.ContainerFromIndex(AssociatedObject.SelectedIndex) as ListBoxItem;
DoubleAnimation fillheightAnimation \= new DoubleAnimation()
{
To \= selectedItemFinalHeight,
Duration \= new Duration(new TimeSpan(0, 0, 0, 0, AnimationDuration))
};
Storyboard.SetTarget(fillheightAnimation, selectedItem);
Storyboard.SetTargetProperty(fillheightAnimation, new PropertyPath(FrameworkElement.HeightProperty));
storyBoard.Children.Add(fillheightAnimation);
}
storyBoard.Begin(AssociatedObject);
}
}
这样ListBox被附加了以上行为。
