我有一个项目，我有一组项目，我想将Canvas绑定到。画布是子类，以提供拖动和调整元素大小的功能。拖动和调整大小的代码工作正常，但问题是我无法绑定画布。我发现我能做到：
<ItemsControl x:Name="Items" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Row="1">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<controls:SuperCanvas Background="Transparent" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemContainerStyle>
<Style TargetType="ContentPresenter">
<Setter Property="Canvas.Left" Value="{Binding Path=X, Mode=TwoWay}" />
<Setter Property="Canvas.Top" Value="{Binding Path=Y, Mode=TwoWay}" />
</Style>
</ItemsControl.ItemContainerStyle>
</ItemsControl>
画布正确绑定，并且画布上显示了项目。但是我的子类画布不再正常工作。 （调整大小并拖动不再起作用。）
以下是SuperCanvas的代码：
sing System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using Meld.Helpers;
namespace Meld.Controls
{
public class SuperCanvas : Canvas
{
private AdornerLayer aLayer;
private bool isDown;
private bool isDragging;
private double originalLeft;
private double originalTop;
private bool selected;
private UIElement selectedElement;
private Point startPoint;
private bool locked;
public SuperCanvas()
{
Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
MouseLeftButtonDown += WorkspaceWindow_MouseLeftButtonDown;
MouseLeftButtonUp += DragFinishedMouseHandler;
MouseMove += WorkspaceWindow_MouseMove;
MouseLeave += Window1_MouseLeave;
PreviewMouseLeftButtonDown += myCanvas_PreviewMouseLeftButtonDown;
PreviewMouseLeftButtonUp += DragFinishedMouseHandler;
}
// Handler for drag stopping on leaving the window
private void Window1_MouseLeave(object sender, MouseEventArgs e)
{
StopDragging();
e.Handled = true;
}
// Handler for drag stopping on user choice
private void DragFinishedMouseHandler(object sender, MouseButtonEventArgs e)
{
StopDragging();
e.Handled = true;
}
// Method for stopping dragging
private void StopDragging()
{
if (isDown)
{
isDown = false;
isDragging = false;
}
}
// Hanler for providing drag operation with selected element
private void WorkspaceWindow_MouseMove(object sender, MouseEventArgs e)
{
if (locked) return;
if (isDown)
{
if ((isDragging == false) &&
((Math.Abs(e.GetPosition(this).X - startPoint.X) >
SystemParameters.MinimumHorizontalDragDistance) ||
(Math.Abs(e.GetPosition(this).Y - startPoint.Y) > SystemParameters.MinimumVerticalDragDistance)))
isDragging = true;
if (isDragging)
{
Point position = Mouse.GetPosition(this);
SetTop(selectedElement, position.Y - (startPoint.Y - originalTop));
SetLeft(selectedElement, position.X - (startPoint.X - originalLeft));
}
}
}
// Handler for clearing element selection, adorner removal
private void WorkspaceWindow_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if (locked) return;
if (selected)
{
selected = false;
if (selectedElement != null)
{
aLayer.Remove(aLayer.GetAdorners(selectedElement)[0]);
selectedElement = null;
}
}
}
// Handler for element selection on the canvas providing resizing adorner
private void myCanvas_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
//add code to lock dragging and dropping things.
if (locked)
{
e.Handled = true;
return;
}
// Remove selection on clicking anywhere the window
if (selected)
{
selected = false;
if (selectedElement != null)
{
// Remove the adorner from the selected element
aLayer.Remove(aLayer.GetAdorners(selectedElement)[0]);
selectedElement = null;
}
}
// If any element except canvas is clicked,
// assign the selected element and add the adorner
if (e.Source != this)
{
isDown = true;
startPoint = e.GetPosition(this);
selectedElement = e.Source as UIElement;
originalLeft = GetLeft(selectedElement);
originalTop = GetTop(selectedElement);
aLayer = AdornerLayer.GetAdornerLayer(selectedElement);
aLayer.Add(new ResizingAdorner(selectedElement));
selected = true;
e.Handled = true;
}
}
}
}
编辑：忘记调整大小的装饰
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
namespace Meld.Helpers
{
internal class ResizingAdorner : Adorner
{
// Resizing adorner uses Thumbs for visual elements.
// The Thumbs have built-in mouse input handling.
Thumb topLeft, topRight, bottomLeft, bottomRight;
// To store and manage the adorner's visual children.
VisualCollection visualChildren;
// Initialize the ResizingAdorner.
public ResizingAdorner(UIElement adornedElement) : base(adornedElement)
{
visualChildren = new VisualCollection(this);
// Call a helper method to initialize the Thumbs
// with a customized cursors.
BuildAdornerCorner(ref topLeft, Cursors.SizeNWSE);
BuildAdornerCorner(ref topRight, Cursors.SizeNESW);
BuildAdornerCorner(ref bottomLeft, Cursors.SizeNESW);
BuildAdornerCorner(ref bottomRight, Cursors.SizeNWSE);
// Add handlers for resizing.
bottomLeft.DragDelta += new DragDeltaEventHandler(HandleBottomLeft);
bottomRight.DragDelta += new DragDeltaEventHandler(HandleBottomRight);
topLeft.DragDelta += new DragDeltaEventHandler(HandleTopLeft);
topRight.DragDelta += new DragDeltaEventHandler(HandleTopRight);
}
// Handler for resizing from the bottom-right.
void HandleBottomRight(object sender, DragDeltaEventArgs args)
{
FrameworkElement adornedElement = this.AdornedElement as FrameworkElement;
Thumb hitThumb = sender as Thumb;
if (adornedElement == null || hitThumb == null) return;
FrameworkElement parentElement = adornedElement.Parent as FrameworkElement;
// Ensure that the Width and Height are properly initialized after the resize.
EnforceSize(adornedElement);
// Change the size by the amount the user drags the mouse, as long as it's larger
// than the width or height of an adorner, respectively.
adornedElement.Width = Math.Max(adornedElement.Width + args.HorizontalChange, hitThumb.DesiredSize.Width);
adornedElement.Height = Math.Max(args.VerticalChange + adornedElement.Height, hitThumb.DesiredSize.Height);
}
// Handler for resizing from the top-right.
void HandleTopRight(object sender, DragDeltaEventArgs args)
{
FrameworkElement adornedElement = this.AdornedElement as FrameworkElement;
Thumb hitThumb = sender as Thumb;
if (adornedElement == null || hitThumb == null) return;
FrameworkElement parentElement = adornedElement.Parent as FrameworkElement;
// Ensure that the Width and Height are properly initialized after the resize.
EnforceSize(adornedElement);
// Change the size by the amount the user drags the mouse, as long as it's larger
// than the width or height of an adorner, respectively.
adornedElement.Width = Math.Max(adornedElement.Width + args.HorizontalChange, hitThumb.DesiredSize.Width);
//adornedElement.Height = Math.Max(adornedElement.Height - args.VerticalChange, hitThumb.DesiredSize.Height);
double height_old = adornedElement.Height;
double height_new = Math.Max(adornedElement.Height - args.VerticalChange, hitThumb.DesiredSize.Height);
double top_old = Canvas.GetTop(adornedElement);
adornedElement.Height = height_new;
Canvas.SetTop(adornedElement, top_old - (height_new - height_old));
}
// Handler for resizing from the top-left.
void HandleTopLeft(object sender, DragDeltaEventArgs args)
{
FrameworkElement adornedElement = AdornedElement as FrameworkElement;
Thumb hitThumb = sender as Thumb;
if (adornedElement == null || hitThumb == null) return;
// Ensure that the Width and Height are properly initialized after the resize.
EnforceSize(adornedElement);
// Change the size by the amount the user drags the mouse, as long as it's larger
// than the width or height of an adorner, respectively.
//adornedElement.Width = Math.Max(adornedElement.Width - args.HorizontalChange, hitThumb.DesiredSize.Width);
//adornedElement.Height = Math.Max(adornedElement.Height - args.VerticalChange, hitThumb.DesiredSize.Height);
double width_old = adornedElement.Width;
double width_new = Math.Max(adornedElement.Width - args.HorizontalChange, hitThumb.DesiredSize.Width);
double left_old = Canvas.GetLeft(adornedElement);
adornedElement.Width = width_new;
Canvas.SetLeft(adornedElement, left_old - (width_new - width_old));
double height_old = adornedElement.Height;
double height_new = Math.Max(adornedElement.Height - args.VerticalChange, hitThumb.DesiredSize.Height);
double top_old = Canvas.GetTop(adornedElement);
adornedElement.Height = height_new;
Canvas.SetTop(adornedElement, top_old - (height_new - height_old));
}
// Handler for resizing from the bottom-left.
void HandleBottomLeft(object sender, DragDeltaEventArgs args)
{
FrameworkElement adornedElement = AdornedElement as FrameworkElement;
Thumb hitThumb = sender as Thumb;
if (adornedElement == null || hitThumb == null) return;
// Ensure that the Width and Height are properly initialized after the resize.
EnforceSize(adornedElement);
// Change the size by the amount the user drags the mouse, as long as it's larger
// than the width or height of an adorner, respectively.
//adornedElement.Width = Math.Max(adornedElement.Width - args.HorizontalChange, hitThumb.DesiredSize.Width);
adornedElement.Height = Math.Max(args.VerticalChange + adornedElement.Height, hitThumb.DesiredSize.Height);
double width_old = adornedElement.Width;
double width_new = Math.Max(adornedElement.Width - args.HorizontalChange, hitThumb.DesiredSize.Width);
double left_old = Canvas.GetLeft(adornedElement);
adornedElement.Width = width_new;
Canvas.SetLeft(adornedElement, left_old - (width_new - width_old));
}
// Arrange the Adorners.
protected override Size ArrangeOverride(Size finalSize)
{
// desiredWidth and desiredHeight are the width and height of the element that's being adorned.
// These will be used to place the ResizingAdorner at the corners of the adorned element.
double desiredWidth = AdornedElement.DesiredSize.Width;
double desiredHeight = AdornedElement.DesiredSize.Height;
// adornerWidth & adornerHeight are used for placement as well.
double adornerWidth = this.DesiredSize.Width;
double adornerHeight = this.DesiredSize.Height;
topLeft.Arrange(new Rect(-adornerWidth / 2, -adornerHeight / 2, adornerWidth, adornerHeight));
topRight.Arrange(new Rect(desiredWidth - adornerWidth / 2, -adornerHeight / 2, adornerWidth, adornerHeight));
bottomLeft.Arrange(new Rect(-adornerWidth / 2, desiredHeight - adornerHeight / 2, adornerWidth, adornerHeight));
bottomRight.Arrange(new Rect(desiredWidth - adornerWidth / 2, desiredHeight - adornerHeight / 2, adornerWidth, adornerHeight));
// Return the final size.
return finalSize;
}
// Helper method to instantiate the corner Thumbs, set the Cursor property,
// set some appearance properties, and add the elements to the visual tree.
void BuildAdornerCorner(ref Thumb cornerThumb, Cursor customizedCursor)
{
if (cornerThumb != null) return;
cornerThumb = new Thumb();
// Set some arbitrary visual characteristics.
cornerThumb.Cursor = customizedCursor;
cornerThumb.Height = cornerThumb.Width = 5;
cornerThumb.Opacity = 0.40;
cornerThumb.Background = new SolidColorBrush(Colors.White);
visualChildren.Add(cornerThumb);
}
// This method ensures that the Widths and Heights are initialized. Sizing to content produces
// Width and Height values of Double.NaN. Because this Adorner explicitly resizes, the Width and Height
// need to be set first. It also sets the maximum size of the adorned element.
void EnforceSize(FrameworkElement adornedElement)
{
if (adornedElement.Width.Equals(Double.NaN))
adornedElement.Width = adornedElement.DesiredSize.Width;
if (adornedElement.Height.Equals(Double.NaN))
adornedElement.Height = adornedElement.DesiredSize.Height;
FrameworkElement parent = adornedElement.Parent as FrameworkElement;
if (parent != null)
{
adornedElement.MaxHeight = parent.ActualHeight;
adornedElement.MaxWidth = parent.ActualWidth;
}
}
// Override the VisualChildrenCount and GetVisualChild properties to interface with
// the adorner's visual collection.
protected override int VisualChildrenCount { get { return visualChildren.Count; } }
protected override Visual GetVisualChild(int index) { return visualChildren[index]; }
}
}
/ END编辑
任何想法为什么在上面的ItemsControl中使用它时不起作用以及如何修复它？
答案 0 :(得分：4)
ItemsControl中的每个项目都由ContentPresenter包装。这是在拖放操作期间需要定位的元素，而不是包含的实际元素。您可以在指定ItemContainerStyle时看到这种情况：
<ItemsControl.ItemContainerStyle>
<Style TargetType="ContentPresenter">
<Setter Property="Canvas.Left" Value="{Binding Path=X, Mode=TwoWay}" />
<Setter Property="Canvas.Top" Value="{Binding Path=Y, Mode=TwoWay}" />
</Style>
</ItemsControl.ItemContainerStyle>
在当前代码中，使用selectedMlement（其附加属性Canvas.Left和Canvas.Top不用于定位元素）在PreviewMouseLeftButtonDown事件中初始化originalLeft和originalTop值。在MouseMove事件中，为selectedElement设置了left和top值，这些值无效，因为它是必须定位的ContentPresenter。
要解决此问题，PreviewMouseLeftButtonDown处理程序应该（类似于）：
selectedElement = e.Source as UIElement;
selectedPresenter = System.Windows.Media.VisualTreeHelper.GetParent(selectedElement) as ContentPresenter;
originalLeft = GetLeft(selectedPresenter);
originalTop = GetTop(selectedPresenter);
在MouseMove处理程序中，您需要使用selectedPresenter而不是selectedElement：
SetTop(selectedPresenter, position.Y - (startPoint.Y - originalTop));
SetLeft(selectedPresenter, position.X - (startPoint.X - originalLeft));
根据您发布的代码，我无法告诉您如何填充ItemsControl或者填充它的内容。为了自己测试，我有一个ObservableCollection绑定到ItemsControl.ItemsSource属性和一个ItemsControl.ItemTemplate，如下所示：
<ItemsControl.ItemTemplate>
<DataTemplate>
<Rectangle Width="100" Height="100" Fill="Blue"></Rectangle>
</DataTemplate>
</ItemsControl.ItemTemplate>
由于数据模板是具有Width和Height属性的FrameworkElement，因此调整大小工作正常。但是，我必须对拖放进行上述更改才能正常工作。