我正在编写我的第一个WPF应用程序。我有一个Canvas，用户可以在其中添加包含表单的UserControl子类。用户应该能够在Canvas周围拖动这些UserControl。使用WPF执行此操作的最佳做法是什么？ 感谢。
答案 0 :(得分：37)
这是在Silverlight中完成的，而不是在WPF中完成的，但它应该是一样的。
在控件上创建两个私有属性：
protected bool isDragging;
private Point clickPosition;
然后在控件的构造函数中附加一些事件处理程序：
this.MouseLeftButtonDown += new MouseButtonEventHandler(Control_MouseLeftButtonDown);
this.MouseLeftButtonUp += new MouseButtonEventHandler(Control_MouseLeftButtonUp);
this.MouseMove += new MouseEventHandler(Control_MouseMove);
现在创建这些方法：
private void Control_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
isDragging = true;
var draggableControl = sender as UserControl;
clickPosition = e.GetPosition(this);
draggableControl.CaptureMouse();
}
private void Control_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
isDragging = false;
var draggable = sender as UserControl;
draggable.ReleaseMouseCapture();
}
private void Control_MouseMove(object sender, MouseEventArgs e)
{
var draggableControl = sender as UserControl;
if (isDragging && draggableControl != null)
{
Point currentPosition = e.GetPosition(this.Parent as UIElement);
var transform = draggableControl.RenderTransform as TranslateTransform;
if (transform == null)
{
transform = new TranslateTransform();
draggableControl.RenderTransform = transform;
}
transform.X = currentPosition.X - clickPosition.X;
transform.Y = currentPosition.Y - clickPosition.Y;
}
}
这里有几点需要注意：
这不一定是在画布上。它也可以在堆叠面板或网格中
2.这使整个控件可拖动，这意味着如果您单击控件中的任意位置并拖动它将拖动整个控件。不确定那是不是你想要的。
编辑 -
扩展您问题中的一些细节：
我实现这个的最好方法是创建一个继承自UserControl的类，可能叫做使用此代码构建的DraggableControl，然后所有可拖动的控件都应该扩展DraggableControl。
编辑2 - 在此控件中有数据网格时，存在一个小问题。如果对数据网格中的列进行排序，则MouseLeftButtonUp事件永远不会触发。我已更新代码，以便isDragging受到保护。我发现最好的解决方案是将此匿名方法绑定到datagrid的LostMouseCapture事件：
this.MyDataGrid.LostMouseCapture += (sender, e) => { this.isDragging = false; };
答案 1 :(得分：2)
Corey的答案大多是正确的，但它缺少一个关键因素：对最后一次转换的记忆。否则，当您移动项目，释放鼠标按钮，然后再次单击该项目时，转换将重置为(0,0)，控件将跳回其原点。
这是一个稍微修改过的版本，对我有用：
public partial class DragItem : UserControl
{
protected Boolean isDragging;
private Point mousePosition;
private Double prevX, prevY;
public DragItem()
{
InitializeComponent();
}
private void UserControl_MouseLeftButtonDown(Object sender, MouseButtonEventArgs e)
{
isDragging = true;
var draggableControl = (sender as UserControl);
mousePosition = e.GetPosition(Parent as UIElement);
draggableControl.CaptureMouse();
}
private void UserControl_MouseLeftButtonUp(Object sender, MouseButtonEventArgs e)
{
isDragging = false;
var draggable = (sender as UserControl);
var transform = (draggable.RenderTransform as TranslateTransform);
if (transform != null)
{
prevX = transform.X;
prevY = transform.Y;
}
draggable.ReleaseMouseCapture();
}
private void UserControl_MouseMove(Object sender, MouseEventArgs e)
{
var draggableControl = (sender as UserControl);
if (isDragging && draggableControl != null)
{
var currentPosition = e.GetPosition(Parent as UIElement);
var transform = (draggableControl.RenderTransform as TranslateTransform);
if (transform == null)
{
transform = new TranslateTransform();
draggableControl.RenderTransform = transform;
}
transform.X = (currentPosition.X - mousePosition.X);
transform.Y = (currentPosition.Y - mousePosition.Y);
if (prevX > 0)
{
transform.X += prevX;
transform.Y += prevY;
}
}
}
}
关键是存储先前的X和Y偏移，然后使用它们来增加当前运动的偏移量，以便得到正确的聚合偏移量。
答案 2 :(得分：1)
如果有人想快速看到这种效果，这是仅使用MouseMove事件的最小解决方案。
布局
<Canvas Background='Beige'
Name='canvas'>
<Rectangle Width='50'
Height='50'
Fill='LightPink'
Canvas.Left='350'
Canvas.Top='175'
MouseMove='Rectangle_MouseMove' />
</Canvas>
背后的代码
private void OnMouseMove(object sender, MouseEventArgs e)
{
if (e.Source is Shape shape)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
Point p = e.GetPosition(canvas);
Canvas.SetLeft(shape, p.X - shape.ActualWidth / 2);
Canvas.SetTop(shape, p.Y - shape.ActualHeight / 2);
shape.CaptureMouse();
}
else
{
shape.ReleaseMouseCapture();
}
}
}
答案 3 :(得分：0)
我在给定的解决方案上遇到了一些麻烦，最终得到了这个：
public partial class UserControlDraggable : UserControl
{
public UserControlDraggable()
{
InitializeComponent();
MouseLeftButtonDown += new MouseButtonEventHandler(Control_MouseLeftButtonDown);
MouseLeftButtonUp += new MouseButtonEventHandler(Control_MouseLeftButtonUp);
MouseMove += new MouseEventHandler(Control_MouseMove);
}
private void Control_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
_isDragging = true;
_mouseLocationWithinMe = e.GetPosition(this);
CaptureMouse();
}
private void Control_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
_isDragging = false;
this.ReleaseMouseCapture();
}
private void Control_MouseMove(object sender, MouseEventArgs e)
{
if (_isDragging)
{
var mouseWithinParent = e.GetPosition(Parent as UIElement);
Canvas.SetLeft(this, mouseWithinParent.X - _mouseLocationWithinMe.X);
Canvas.SetTop(this, mouseWithinParent.Y - _mouseLocationWithinMe.Y);
}
}
protected bool _isDragging;
Point _mouseLocationWithinMe;
}
这基本上是Corey的例子，但它充分利用了Hawlett的暗示。它仅在父容器是Canvas时才有效。此外，它应该受到一些限制，以防止用户将控件拖到它真正不应该的位置。
答案 4 :(得分：0)
Button newBtn = new Button();
newBtn.AddHandler(Button.ClickEvent, new RoutedEventHandler(BtTable_Click));
newBtn.AddHandler(Button.PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(BtTable_MouseLeftButtonDown));
newBtn.AddHandler(Button.PreviewMouseLeftButtonUpEvent, new MouseButtonEventHandler(BtTable_MouseLeftButtonUp));
newBtn.AddHandler(Button.PreviewMouseMoveEvent, new MouseEventHandler(BtTable_MouseMove));
private object movingObject;
private double firstXPos, firstYPos;
private int ButtonSize = 50;
private void BtTable_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
Button newBtn = sender as Button;
Canvas canvas = newBtn.Parent as Canvas;
firstXPos = e.GetPosition(newBtn).X;
firstYPos = e.GetPosition(newBtn).Y - ButtonSize;
movingObject = sender;
// Put the image currently being dragged on top of the others
int top = Canvas.GetZIndex(newBtn);
foreach (Button child in canvas.Children)
if (top < Canvas.GetZIndex(child))
top = Canvas.GetZIndex(child);
Canvas.SetZIndex(newBtn, top + 1);
Mouse.Capture(null);
}
private void BtTable_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
Button newBtn = sender as Button;
Canvas canvas = newBtn.Parent as Canvas;
movingObject = null;
// Put the image currently being dragged on top of the others
int top = Canvas.GetZIndex(newBtn);
foreach (Button child in canvas.Children)
if (top > Canvas.GetZIndex(child))
top = Canvas.GetZIndex(child);
Canvas.SetZIndex(newBtn, top + 1);
Mouse.Capture(newBtn);
}
private void BtTable_MouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed && sender == movingObject)
{
Button newBtn = sender as Button;
Canvas canvas = newBtn.Parent as Canvas;
// Horizontal
double newLeft = e.GetPosition(canvas).X - firstXPos - canvas.Margin.Left;
// newLeft inside canvas right-border?
if (newLeft > canvas.Margin.Left + canvas.ActualWidth - newBtn.ActualWidth)
newLeft = canvas.Margin.Left + canvas.ActualWidth - newBtn.ActualWidth;
// newLeft inside canvas left-border?
else if (newLeft < canvas.Margin.Left)
newLeft = canvas.Margin.Left;
newBtn.SetValue(Canvas.LeftProperty, newLeft);
//Vertical
double newTop = e.GetPosition(canvas).Y - firstYPos - canvas.Margin.Top;
// newTop inside canvas bottom-border?
// -- Bottom --
if (newTop > canvas.Margin.Top + canvas.ActualHeight - newBtn.ActualHeight - ButtonSize)
newTop = canvas.Margin.Top + canvas.ActualHeight - newBtn.ActualHeight - ButtonSize;
// newTop inside canvas top-border?
// -- Top --
else if (newTop < canvas.Margin.Top - ButtonSize)
newTop = canvas.Margin.Top - ButtonSize;
newBtn.SetValue(Canvas.TopProperty, newTop);
}
}
快乐编码;）
答案 5 :(得分：-1)
我为WPF和UWP商店应用实现了这个功能。并且在用户控件本身而不是使用它的控件中添加了所有代码，您可以根据需要对其进行修改。
<强> WPF
public partial class DragUserControl : UserControl
{
public DragUserControl()
{
InitializeComponent();
}
object MovingObject;
double FirstXPos, FirstYPos;
private void Button_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
this.MovingObject = this;
FirstXPos = e.GetPosition(MovingObject as Control).X;
FirstYPos = e.GetPosition(MovingObject as Control).Y;
Canvas canvas = this.Parent as Canvas;
if (canvas != null)
{
canvas.PreviewMouseMove += this.MouseMove;
}
}
private void MouseMove(object sender, MouseEventArgs e)
{
/*
* In this event, at first we check the mouse left button state. If it is pressed and
* event sender object is similar with our moving object, we can move our control with
* some effects.
*/
Canvas canvas = sender as Canvas;
Point canvasPoint = e.GetPosition(canvas);
Point objPosition = e.GetPosition((MovingObject as FrameworkElement));
if (e.LeftButton == MouseButtonState.Pressed)
{
if (MovingObject != null)
{
//This condition will take care that control should not go outside the canvas.
if ((e.GetPosition((MovingObject as FrameworkElement).Parent as FrameworkElement).X - FirstXPos > 0) && (e.GetPosition((MovingObject as FrameworkElement).Parent as FrameworkElement).X - FirstXPos < canvas.ActualWidth - (MovingObject as FrameworkElement).ActualWidth))
{
(MovingObject as FrameworkElement).SetValue(Canvas.LeftProperty, e.GetPosition((MovingObject as FrameworkElement).Parent as FrameworkElement).X - FirstXPos);
}
//This condition will take care that control should not go outside the canvas.
if ((e.GetPosition((MovingObject as FrameworkElement).Parent as FrameworkElement).Y - FirstYPos > 0) && (e.GetPosition((MovingObject as FrameworkElement).Parent as FrameworkElement).Y - FirstYPos < canvas.ActualHeight - (MovingObject as FrameworkElement).ActualHeight))
{
(MovingObject as FrameworkElement).SetValue(Canvas.TopProperty, e.GetPosition((MovingObject as FrameworkElement).Parent as FrameworkElement).Y - FirstYPos);
}
}
}
}
private void Ellipse_PreviewMouseLeftButtonUp_1(object sender, MouseButtonEventArgs e)
{
MovingObject = null;
}
}
Button_MouseLeftButtonDown是您想要拖动控件的按钮的单击事件。
<强> UWP
public sealed partial class DragUserControl : UserControl
{
MovingObject;
double FirstXPos, FirstYPos;
public DragUserControl()
{
InitializeComponent();
}
private void Ellipse_PointerPressed(object sender, PointerRoutedEventArgs e)
{
this.MovingObject = this;
FirstXPos = e.GetCurrentPoint(MovingObject as Control).Position.X;
FirstYPos = e.GetCurrentPoint(MovingObject as Control).Position.Y;
Canvas canvas = this.Parent as Canvas;
if (canvas != null)
{
canvas.PointerMoved += Canvas_PointerMoved;
}
}
private void Canvas_PointerMoved(object sender, PointerRoutedEventArgs e)
{
if (MovingObject != null)
{
Canvas canvas = sender as Canvas;
Point canvasPoint = e.GetCurrentPoint(canvas).Position;
Point objPosition = e.GetCurrentPoint((MovingObject as FrameworkElement)).Position;
if (e.GetCurrentPoint(MovingObject as Control).Properties.IsLeftButtonPressed) //e.Pointer.IsInContact ==true)
{
//This condition will take care that control should not go outside the canvas
if ((e.GetCurrentPoint((MovingObject as FrameworkElement).Parent as FrameworkElement).Position.X - FirstXPos > 0) && (e.GetCurrentPoint((MovingObject as FrameworkElement).Parent as FrameworkElement).Position.X - FirstXPos < canvas.ActualWidth - (MovingObject as FrameworkElement).ActualWidth))
{
(MovingObject as FrameworkElement).SetValue(Canvas.LeftProperty, e.GetCurrentPoint((MovingObject as FrameworkElement).Parent as FrameworkElement).Position.X - FirstXPos);
}
//This condition will take care that control should not go outside the canvas
if ((e.GetCurrentPoint((MovingObject as FrameworkElement).Parent as FrameworkElement).Position.Y - FirstYPos > 0) && (e.GetCurrentPoint((MovingObject as FrameworkElement).Parent as FrameworkElement).Position.Y - FirstYPos < canvas.ActualHeight - (MovingObject as FrameworkElement).ActualHeight))
{
(MovingObject as FrameworkElement).SetValue(Canvas.TopProperty, e.GetCurrentPoint((MovingObject as FrameworkElement).Parent as FrameworkElement).Position.Y - FirstYPos);
}
}
}
}
private void Ellipse_PointerReleased(object sender, PointerRoutedEventArgs e)
{
MovingObject = null;
}
}
Ellipse_PointerPressed是您想要拖动控件的椭圆的click事件。