[转载]WPF控件拖动

这篇博文总结下WPF中的拖动，文章内容主要包括：

1.拖动窗口

2.拖动控件 Using Visual Studio

　　2.1thumb控件

　　2.2Drag、Drop（不连续，没有中间动画）

　　2.3拖动一个控件

　　2.4让一个窗口内的所有(指定的)控件可拖动

3.Expression Blend X实现拖动(Best Practice)

小结

1.拖动窗口

我们知道，鼠标放在窗口的标题栏上按下就可以拖动窗体。我们要实现在窗口的全部地方或特定地方按下鼠标左键实现拖动。

Winform的做法是，获取鼠标的位置信息，从而设置窗体的位置。

WPF也可以采用Winform类似的方法，但是没有必要，因为有更加单的方法。

<Window x:Class="WpfApplicationDrugMove.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="窗体拖动" Height="350" Width="525">
    <Grid Background="Green" MouseLeftButtonDown="Grid_MouseLeftButtonDown">
        <Canvas Height="65" Background="Gray" HorizontalAlignment="Left" Margin="284,110,0,0" Name="canvas1" VerticalAlignment="Top" Width="74" MouseLeftButtonDown="canvas1_MouseLeftButtonDown">

        </Canvas>
    </Grid>
</Window>

有Grid布局的窗口，里面放置了一个Canvas。
要实现在Grid内按下鼠标左键实现窗体拖动/或是Canvas内实现按下鼠标左键实现窗体拖动，代码如下：

private void canvas1_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
   base.DragMove();//实现整个窗口的拖动
}

private void Grid_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
   base.DragMove();
}

从上面的代码我们可以看到，DragMove()方法仅用来实现窗体的拖动。

2.拖动控件

2.1thumb控件

thumb控件MSDN的描述非常简单：Represents a control that can be dragged by the user.（表示可由用户拖动的控件）。

由DragStarted、DragDelta、DragCompleted着三个事件完成控件的拖动。

给个例子：我们在Canvas中加入如下thumb控件

<Thumb Name="thumb1" Background="Red" Height="50" Width="100" DragDelta="DragDelta" DragStarted="DragStarted" DragCompleted="DragCompleted" Canvas.Left="335" Canvas.Top="121" />  

实现相应的事件，即可完成该控件的拖动工作。

private void DragDelta(object sender, System.Windows.Controls.Primitives.DragDeltaEventArgs e)
{
   Canvas.SetLeft(thumb1,Canvas.GetLeft(thumb1)+e.HorizontalChange);
   Canvas.SetTop(thumb1, Canvas.GetTop(thumb1) + e.VerticalChange);
}

private void DragStarted(object sender, System.Windows.Controls.Primitives.DragStartedEventArgs e)
{
   thumb1.Background = Brushes.White;
}

private void DragCompleted(object sender, System.Windows.Controls.Primitives.DragCompletedEventArgs e)
{
   thumb1.Background = Brushes.Red;
}

这只是一个简单的示例，我们知道thumb有拇指的意思，代表着很棒的意思。
sukram在2008-08-23在codeproject上发表的WPF Diagram Designer(WPF图形设计器)系列文章(共3篇)，被国内很多人Copy过来说是他自己弄的（吐槽：这里省去3K字），其中关于thumb的运用可供参考，thumb可以实现控件的拖动。

2.2 drag、drop（不连续，没有中间动画）

很多控件都有AllowDrop属性：允许放下；和Drop事件。

给出两个例子。

例1：

<Grid>
  <Label Name ="label1" Content="TestDrop" Background="Red" Height ="28" HorizontalAlignment="Left" Margin="70,35,0,0"  VerticalAlignment="Top" MouseDown="label1_MouseDown"  />
  <Label Name="label2"  Content="ToHere"  Background="Green" Height="28" HorizontalAlignment="Left" Margin ="342,107,0,0"  VerticalAlignment="Top" AllowDrop ="True" Drop="tagert_drop"   />
</Grid>

现在，拖拽label1到label上，把label1的text赋值给label2.实现如下：

private void label1_MouseDown(object sender, MouseButtonEventArgs e)
{
    Label lbl = (Label)sender;
    DragDrop.DoDragDrop(lbl, lbl.Content, DragDropEffects.Copy);
}
private void tagert_drop(object sender, DragEventArgs e)
{
    ((Label)sender).Content = e.Data.GetData(DataFormats.Text);
}

例2：

界面上有两个Canvas，右面的Canvas里面有一个Rectangle。拖动右面的Rectangle把它拖到左边来，并且保留右边的Rectangle。

<Window x:Class="WpfApplicationDrugMove.Windowdragdrop"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Windowdragdrop" Height="369" Width="559">
    <Grid>
        <Canvas Background="ForestGreen" Height="282" HorizontalAlignment="Left" Margin="22,20,0,0" Name="canvas1" VerticalAlignment="Top" Width="226" />
        <Canvas Background="ForestGreen" Height="282" HorizontalAlignment="Left" Margin="278,20,0,0" Name="canvas2" VerticalAlignment="Top" Width="232">
            <Rectangle Fill="Yellow" Canvas.Left="35" Canvas.Top="36" Height="100" Name="rectangle1" Stroke="Black" Width="150" />
        </Canvas>
    </Grid>
</Window>

namespace WpfApplicationDrugMove
{
    /// <summary>
    /// Interaction logic for Windowdragdrop.xaml
    /// </summary>
    public partial class Windowdragdrop : Window
    {
        public Windowdragdrop()
        {
            InitializeComponent();

            canvas1.AllowDrop = true;
            rectangle1.PreviewMouseMove += new MouseEventHandler(rectangle1_PreviewMouseMove);
            canvas1.DragOver += new DragEventHandler(canvas1_DragOver);
            canvas1.Drop += new DragEventHandler(canvas1_Drop);
        }     

        void rectangle1_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed)
            {
                DataObject data = new DataObject(typeof(Rectangle), rectangle1);
                DragDrop.DoDragDrop(rectangle1, data, DragDropEffects.Copy);
            }
        }

        void canvas1_Drop(object sender, DragEventArgs e)
        {
            IDataObject data = new DataObject();
            data = e.Data;
            if (data.GetDataPresent(typeof(Rectangle)))
            {
                Rectangle rect = new Rectangle();
                rect = data.GetData(typeof(Rectangle)) as Rectangle;
                //canvas2.Children.Remove(rect);
                //canvas1.Children.Add(rect);
                //序列化Control,以深复制Control!!!!
                string rectXaml = XamlWriter.Save(rect);
                StringReader stringReader = new StringReader(rectXaml);
                XmlReader xmlReader = XmlReader.Create(stringReader);
                UIElement clonedChild = (UIElement)XamlReader.Load(xmlReader);
                canvas1.Children.Add(clonedChild);
            }
        }

        void canvas1_DragOver(object sender, DragEventArgs e)
        {
            if(!e.Data.GetDataPresent(typeof(Rectangle)))
            {
                e.Effects = DragDropEffects.None;
                e.Handled = true;
            }

        }

    }
}

效果如下：

这个也就回答了博客园的一篇博问：WPF拖拽实现

虽然这个问题被标记为解决，但是其解决的方法过于丑陋，具体请看DebugLZQ本文代码实现。

2.3拖动一个控件

实现和thumb一样的效果，不同于drag/drop，拖动的时候控件跟随鼠标移动。

<Canvas x:Name="canvas1" Background="Green">
  <Canvas  Background="Yellow" Canvas.Left="85" Canvas.Top="51" Height="100" Name="canvas2" Width="105" MouseLeftButtonDown="canvas2_MouseDown"   MouseMove="canvas2_MouseMove" MouseLeftButtonUp="canvas2_MouseLeftButtonUp"></Canvas>
</Canvas>

Canvas中又一个控件(Canvas2)，实现canvas2的拖动。

实现canvas2的MouseLeftButtonDown、MouseMove、MouseLeftButtonUp事件。

Point oldPoint = new Point();
bool isMove = false;
private void canvas2_MouseMove(object sender, MouseEventArgs e)
{
   if (isMove)
   {
       canvas2.Background = Brushes.White;

       FrameworkElement currEle = sender as FrameworkElement;
       double xPos = e.GetPosition(null).X - oldPoint.X + (double)currEle.GetValue(Canvas.LeftProperty);
       double yPos = e.GetPosition(null).Y - oldPoint.Y + (double)currEle.GetValue(Canvas.TopProperty);
       currEle.SetValue(Canvas.LeftProperty, xPos);
       currEle.SetValue(Canvas.TopProperty, yPos);

       oldPoint = e.GetPosition(null);
   }
}

private void canvas2_MouseDown(object sender, MouseButtonEventArgs e)
{
   isMove = true;
   oldPoint = e.GetPosition(null);
}

private void canvas2_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
   isMove = false;
   canvas2.Background = Brushes.Yellow;
}

2.4让一个窗口内的所有(指定的)控件可拖动

有2.3的基础，现在我们就可以很方便的实现容器内所有控件拖动了。不仅仅局限于Canvas。其实Canvas的绝对定位和其他的容器(如Grid)没多好差别，只不过Canvas使用Left/Top来定位；Grid是用Margin，仅此而已！

1.还是Canvas中的拖动

<Window x:Class="WpfApplicationDrugMove.WindowWPFALLControlDragInCanvas"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="WindowWPFALLControlDragInCanvas" Height="418" Width="642">
    <Canvas x:Name="LayoutRoot" Background="Violet">
        <Label Canvas.Left="330" Canvas.Top="151" Content="Label" Height="28" Name="label1" />
        <TextBlock Canvas.Left="437" Canvas.Top="154" Height="23" Name="textBlock1" Text="TextBlock" />
        <Image Canvas.Left="206" Canvas.Top="231" Height="64" Name="image1" Stretch="Fill" Width="73" Source="/WpfApplicationDrugMove;component/1.jpg" />
        <Canvas Canvas.Left="358" Canvas.Top="233" Height="100" Name="canvas1" Width="200"  Background="Red"></Canvas>
        <Button Canvas.Left="227" Canvas.Top="38" Content="Button" Height="23" Name="button1" Width="75" />
        <TextBox Canvas.Left="113" Canvas.Top="125" Height="23" Name="textBox1" Width="120" />
    </Canvas>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace WpfApplicationDrugMove
{
    /// <summary>
    /// Interaction logic for WindowWPFALLControlDrag.xaml
    /// </summary>
    public partial class WindowWPFALLControlDragInCanvas:Window
    {
        public WindowWPFALLControlDragInCanvas()
        {
            InitializeComponent();

            foreach (UIElement uiEle in LayoutRoot.Children)
            {
                //WPF设计上的问题,Button.Clicked事件Supress掉了Mouse.MouseLeftButtonDown附加事件等.
                //不加这个Button、TextBox等无法拖动
                if (uiEle is Button||uiEle is TextBox)
                {
                    uiEle.AddHandler(Button.MouseLeftButtonDownEvent, new MouseButtonEventHandler(Element_MouseLeftButtonDown), true);
                    uiEle.AddHandler(Button.MouseMoveEvent, new MouseEventHandler(Element_MouseMove),true);
                    uiEle.AddHandler(Button.MouseLeftButtonUpEvent, new MouseButtonEventHandler(Element_MouseLeftButtonUp), true);
                    continue;
                }
                //
                uiEle.MouseMove += new MouseEventHandler(Element_MouseMove);
                uiEle.MouseLeftButtonDown += new MouseButtonEventHandler(Element_MouseLeftButtonDown);
                uiEle.MouseLeftButtonUp += new MouseButtonEventHandler(Element_MouseLeftButtonUp);
            }
        }

        bool isDragDropInEffect = false;
        Point pos = new Point();

        void Element_MouseMove(object sender, MouseEventArgs e)
        {
            if (isDragDropInEffect)
            {
                FrameworkElement currEle = sender as FrameworkElement;
                double xPos = e.GetPosition(null).X - pos.X + (double)currEle.GetValue(Canvas.LeftProperty);
                double yPos = e.GetPosition(null).Y - pos.Y + (double)currEle.GetValue(Canvas.TopProperty);
                currEle.SetValue(Canvas.LeftProperty, xPos);
                currEle.SetValue(Canvas.TopProperty, yPos);
                pos = e.GetPosition(null);
            }
        } 

        void Element_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {

            FrameworkElement fEle = sender as FrameworkElement;
            isDragDropInEffect = true;
            pos = e.GetPosition(null);
            fEle.CaptureMouse();
            fEle.Cursor = Cursors.Hand;
        }

        void Element_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if (isDragDropInEffect)
            {
                FrameworkElement ele = sender as FrameworkElement;
                isDragDropInEffect = false;
                ele.ReleaseMouseCapture();
            }
        } 

    }
}

注意：需要用AddHandler添加Button.MouseLeftButtonDown等事件，不然无法触发，因为Button.Clicked事件Supress掉了MouseLeftButtonDown。
这样页面上的所有控件就可以随意拖动了。

今天在CodeProject上看到了这篇文章：WPF - Catch Events Even if they are Already Handled，说的是一个事情。

2.Canvas换成Grid。Grid中所有控件可拖动。

<Window x:Class="WpfApplicationDrugMove.WindowWPFALLControlDragMoveInGrid"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="WindowWPFALLControlDragMoveInGrid" Height="382" Width="552">
    <Grid x:Name="LayoutRoot" Background="GreenYellow">
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="60,42,0,0" Name="button1" VerticalAlignment="Top" Width="75" />
        <Label Content="Label" Height="28" HorizontalAlignment="Left" Margin="305,89,0,0" Name="label1" VerticalAlignment="Top" />
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="204,45,0,0" Name="button2" VerticalAlignment="Top" Width="75" />
        <TextBlock Height="23" HorizontalAlignment="Left" Margin="363,42,0,0" Name="textBlock1" Text="TextBlock" VerticalAlignment="Top" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="60,140,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" />
        <Image Height="56" HorizontalAlignment="Left" Margin="173,229,0,0" Name="image1" Stretch="Fill" VerticalAlignment="Top" Width="62" Source="/WpfApplicationDrugMove;component/1.jpg" />
        <Image Height="150" HorizontalAlignment="Left" Margin="291,159,0,0" Name="image2" Stretch="Fill" VerticalAlignment="Top" Width="177" Source="/WpfApplicationDrugMove;component/2.gif" />
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace WpfApplicationDrugMove
{
    /// <summary>
    /// Interaction logic for WindowWPFALLControlDragMoveInGrid.xaml
    /// </summary>
    public partial class WindowWPFALLControlDragMoveInGrid : Window
    {
        public WindowWPFALLControlDragMoveInGrid()
        {
            InitializeComponent();

            foreach (UIElement uiEle in LayoutRoot.Children)
            {
                if (uiEle is Button || uiEle is TextBox)
                {
                    uiEle.AddHandler(Button.MouseLeftButtonDownEvent, new MouseButtonEventHandler(Element_MouseLeftButtonDown), true);
                    uiEle.AddHandler(Button.MouseMoveEvent, new MouseEventHandler(Element_MouseMove), true);
                    uiEle.AddHandler(Button.MouseLeftButtonUpEvent, new MouseButtonEventHandler(Element_MouseLeftButtonUp), true);
                    continue;
                }
                uiEle.MouseMove += new MouseEventHandler(Element_MouseMove);
                uiEle.MouseLeftButtonDown += new MouseButtonEventHandler(Element_MouseLeftButtonDown);
                uiEle.MouseLeftButtonUp += new MouseButtonEventHandler(Element_MouseLeftButtonUp);
            }
        }

        bool isDragDropInEffect = false;
        Point pos = new Point();

        void Element_MouseMove(object sender, MouseEventArgs e)
        {
            if (isDragDropInEffect)
            {
                FrameworkElement currEle = sender as FrameworkElement;
                double xPos = e.GetPosition(null).X - pos.X + currEle.Margin.Left;
                double yPos = e.GetPosition(null).Y - pos.Y + currEle.Margin.Top;
                currEle.Margin = new Thickness(xPos, yPos, 0, 0);
                pos = e.GetPosition(null);
            }
        }

        void Element_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {

            FrameworkElement fEle = sender as FrameworkElement;
            isDragDropInEffect = true;
            pos = e.GetPosition(null);
            fEle.CaptureMouse();
            fEle.Cursor = Cursors.Hand;
        }

        void Element_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if (isDragDropInEffect)
            {
                FrameworkElement ele = sender as FrameworkElement;
                isDragDropInEffect = false;
                ele.ReleaseMouseCapture();
            }
        } 

    }
}

效果如下：

Grid界面中的所有控件可随意拖动。

3.使用Expression Blend实现拖动(Best Practice)

使用如下的一个Behavior：MouseDragElementBehavior

实现方法非常简单，let's say 我们有个Rectangle，无论在什么容器中，我们要实现其拖动。

直接把这个MouseDragElementBehavior 拖动到Rectangle中即可。

XAML如下：

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"  x:Class="WPFDragMoveBlend.MainWindow"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Rectangle Fill="Red" Stroke="Black" Margin="145,82,164,50" Width="200" Height="180" >
            <i:Interaction.Behaviors>
                <ei:MouseDragElementBehavior/>
            </i:Interaction.Behaviors>
        </Rectangle>
    </Grid>
</Window>

(如您所见，DebugLZQ使用的是 Expression Blend 4)。
程序运行正常，Rectangle可随意拖动如下：

使用Blend借助Behaviors不需要额外的C#代码，最为简洁。

其他的一些Behaviors也非常有用，

如播放MP3：

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"  x:Class="WPFDragMoveBlend.MainWindow"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Rectangle Fill="Red" Stroke="Black" Margin="145,82,164,50" Width="200" Height="180" >
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="MouseLeftButtonDown">
                    <ei:PlaySoundAction Source="C:\Users\Public\Music\Sample Music\Kalimba.mp3"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>

            <i:Interaction.Behaviors>
                <ei:MouseDragElementBehavior/>
            </i:Interaction.Behaviors>
        </Rectangle>
    </Grid>
</Window>

程序可正常运行。

还有如CallMethodAction，ControlStoryboardAction，及MVVM中使用较多的InvokeCommandAction等。

小结一下：

关于2.2例2中控件的序列化、反序列化! 参考：WPF控件深拷贝:序列化/反序列化

关于Button.MouseLeftButtonDown用C#代码注册的话需要用AddHandler添加，直接添加会被Button.Clicked阻止! 另一种情况是：我们如何捕获一个路由事件，即使这个路由事件已经被标记为e.handled=true。这个很重要！！！参考：WPF捕获事件即使这个事件被标记为Handled  。拖动不局限于Canvas.

所有方法中，Blend实现最为Clearn.关于Blend 4的快捷键，请参考：A Complete Guide to Expression Blend 4 Shortcut Keys

老鸟绕过，轻拍~

Wish it helps.

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