我有一个Collection项绑定到ItemsControl元素。
我需要为每个元素启用鼠标拖动行为，但我似乎无法使其正常工作。
添加此代码
<i:Interaction.Behaviors>
<el:MouseDragElementBehavior/>
</i:Interaction.Behaviors>
只有当我将我的项目放在ItemsControl之外时才会有效。
以下是ItemsControl组件的代码：
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<utils:TemplateSelector Content="{Binding}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
我做错了吗？
编辑：新代码但仍无效（使用和不使用Canvas）
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<utils:TemplateSelector Content="{Binding}">
<i:Interaction.Behaviors>
<el:MouseDragElementBehavior/>
</i:Interaction.Behaviors>
</utils:TemplateSelector>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
答案 0 :(得分：3)
似乎一旦你开始赏金，你突然找到了一个你在过去几个月里找不到的解决方案。
我正在回答添加我的解决方案，目前有效，但肯定可以做得更好。
我建议的是基于两个不同的来源：
让我们从XAML开始：
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border BorderBrush="{StaticResource PhoneForegroundBrush}">
<utils:TemplateSelector Content="{Binding}"/>
<toolkit:GestureService.GestureListener>
<toolkit:GestureListener
DragStarted="GestureListener_OnDragStarted"
DragDelta="GestureListener_OnDragDelta"
DragCompleted="GestureListener_OnDragCompleted"/>
</toolkit:GestureService.GestureListener>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas x:Name="WidgetsCanvas" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
（toolkit来自Windows Phone Toolkit）
现在让我们看看三个拖动处理程序的实现。
private int _zindex; //Used to keep the moved element on the top, not working for now
private FrameworkElement _movedObject; //The element that we're moving. Used to avoid moving multiple items if they overlap
private void GestureListener_OnDragStarted(object sender, DragStartedGestureEventArgs e)
{
if (_movedObject != null) return; // We're already moving something!
// Initialize the drag
var fe = sender as FrameworkElement; // The element that we want to move
(fe as Border).BorderThickness = new Thickness(5); // A simple effect to mark the element on the screen
_movedObject = fe; // We set the current object to the one which is moving
Canvas.SetZIndex(fe, _zindex++); // This should take the moved object on the top but it's not working
}
private void GestureListener_OnDragDelta(object sender, DragDeltaGestureEventArgs e)
{
var fe = sender as FrameworkElement;
if (!fe.Equals(_movedObject)) return; // We change the object's position only if this is the one who started the event
var offset = DragManager.GetOffset(fe); // We get the current position
var canvas = DragManager.FindChild<Canvas>(Application.Current.RootVisual, "ItemsCanvas"); // We need the container of our object to force it to stay inside the container
//The new position is given by the old one plus the change reported by the event
var horizontalOffset = offset.HorizontalValue + e.HorizontalChange;
var verticalOffset = offset.VerticalValue + e.VerticalChange;
// We need to check if the new position is outside our container's bounds
if (horizontalOffset < 0) horizontalOffset = 0;
else if (horizontalOffset > (canvas.ActualWidth - fe.ActualWidth)) horizontalOffset = canvas.ActualWidth - fe.ActualWidth;
if (verticalOffset < 0) verticalOffset = 0;
else if (verticalOffset > (canvas.ActualHeight - fe.ActualHeight)) verticalOffset = canvas.ActualHeight - fe.ActualHeight;
// Once we've got everything set, we can move our component
DragManager.SetOffset(fe, horizontalOffset, verticalOffset);
}
private void GestureListener_OnDragCompleted(object sender, DragCompletedGestureEventArgs e)
{
var fe = sender as FrameworkElement;
(fe as Border).BorderThickness = new Thickness(0); // We undo our effect
_movedObject = null; // The movement is done so we can reset our current object and wait for a new one to come
}
处理程序使用我称为DragManager的类。它的代码非常简单：
public static class DragManager
{
public static void SetOffset(FrameworkElement fe, double horizontalOffset, double verticalOffset)
{
var trans = new TranslateTransform
{
X = horizontalOffset,
Y = verticalOffset
};
// I don't know what may change, in terms of performance, between applying the transform or just changing the margins. I'm using the margins because the transform may be needed for some other purpose
//fe.RenderTransform = trans;
fe.Margin = new Thickness(horizontalOffset, verticalOffset, 0, 0); // We just change our object's margins to reflect its new position
// We store the current position in the objects Tag (maybe there's a better solution but I'm quite new to C#/xaml)
fe.Tag = new Offset
{
VerticalValue = verticalOffset,
HorizontalValue = horizontalOffset,
Transform = trans
};
}
public static Offset GetOffset(FrameworkElement fe)
{
if (fe.Tag == null) fe.Tag = new Offset();
return (Offset)fe.Tag;
}
public struct Offset
{
public double HorizontalValue { get; set; }
public double VerticalValue { get; set; }
public TranslateTransform Transform { get; set; }
}
public static T FindChild<T>(DependencyObject parent, string childName) where T : DependencyObject
{
// Confirm parent and childName are valid.
if (parent == null)
{
return null;
}
T foundChild = null;
var childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (var i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
// If the child is not of the request child type child
var childType = child as T;
if (childType == null)
{
// recursively drill down the tree
foundChild = FindChild<T>(child, childName);
// If the child is found, break so we do not overwrite the found child.
if (foundChild != null)
{
break;
}
}
else if (!String.IsNullOrEmpty(childName))
{
var frameworkElement = child as FrameworkElement;
// If the child's name is set for search
if (frameworkElement != null && frameworkElement.Name == childName)
{
// if the child's name is of the request name
foundChild = (T)child;
break;
}
// Need this in case the element we want is nested
// in another element of the same type
foundChild = FindChild<T>(child, childName);
}
else
{
// child element found.
foundChild = (T)child;
break;
}
}
return foundChild;
}
}
正如我已经说过的，这段代码现在正在运作。
如果有人提出改进建议，请在此处写一下，以便我可以看到/测试更好的方法来做这类事情！