1.创建拖放对象
1.1创建一个圆自定义控件，UI代码如下(Circle.xaml)：
<UserControl x:Class="WpfApp1.Circle"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800"
AllowDrop="True">
<Grid>
<Ellipse x:Name="circleUI"
Height="100" Width="100"
Fill="Blue" />
</Grid>
</UserControl>
1.2Circle.xaml.cs文件输入以下代码
1.2.0 自定义变量声明
/// <summary>
/// 用于存放原有brush值，便于撤销操作
/// </summary>
private Brush _previousFill = null;
1.2.1 添加带参数构造函数
public Circle(Circle c)
{
InitializeComponent();
this.circleUI.Height = c.circleUI.Height;
this.circleUI.Width = c.circleUI.Height;
this.circleUI.Fill = c.circleUI.Fill;
}
1.2.2 onm ouseMove事件重写，主要是用于将圆对象数据打包到DataObject对象
/// <summary>
/// 1.将圆形数据打包到 DataObject
/// 2.调用静态 DragDrop.DoDragDrop 方法启动拖放操作
/// </summary>
/// <param name="e"></param>
protected override void onm ouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);
if (e.LeftButton == MouseButtonState.Pressed)
{
// Package the data.
DataObject data = new DataObject();
data.SetData(DataFormats.StringFormat, circleUI.Fill.ToString());
data.SetData("Double", circleUI.Height);
data.SetData("Object", this);
// Initiate the drag-and-drop operation.
DragDrop.DoDragDrop(this, data, DragDropEffects.Copy | DragDropEffects.Move);
}
}
1.2.3 自定义拖拽过程中鼠标显示样式
/// <summary>
/// 设置自定义光标
/// </summary>
/// <param name="e"></param>
protected override void OnGiveFeedback(GiveFeedbackEventArgs e)
{
base.OnGiveFeedback(e);
// These Effects values are set in the drop target's
// DragOver event handler.
if (e.Effects.HasFlag(DragDropEffects.Copy))
{
Mouse.SetCursor(Cursors.Cross);
}
else if (e.Effects.HasFlag(DragDropEffects.Move))
{
Mouse.SetCursor(Cursors.Pen);
}
else
{
Mouse.SetCursor(Cursors.No);
}
e.Handled = true;
}
1.2.4 处理已放置数据
/// <summary>
/// 处理已放置数据
/// </summary>
/// <param name="e"></param>
protected override void OnDrop(DragEventArgs e)
{
base.OnDrop(e);
// 使用 GetDataPresent 方法检查拖动的数据是否包含字符串对象
if (e.Data.GetDataPresent(DataFormats.StringFormat))
{
//使用 GetData 方法提取字符串数据
string dataString = (string)e.Data.GetData(DataFormats.StringFormat);
//使用 BrushConverter 尝试将字符串转换为 Brush
BrushConverter converter = new BrushConverter();
if (converter.IsValid(dataString))
{
Brush newFill = (Brush)converter.ConvertFromString(dataString);
//将画笔应用于提供圆形控件的 UI 的 Ellipse 的 Fill
circleUI.Fill = newFill;
// 判断是否按下ctrl键
if (e.KeyStates.HasFlag(DragDropKeyStates.ControlKey))
{
1.2.5 验证是否允许数据放置
/// <summary>
/// 验证是否允许数据放置
/// </summary>
/// <param name="e"></param>
protected override void OnDragOver(DragEventArgs e)
{
base.OnDragOver(e);
e.Effects = DragDropEffects.None;
// 使用 GetDataPresent 方法检查拖动的数据是否包含字符串对象
if (e.Data.GetDataPresent(DataFormats.StringFormat))
{
//使用 GetData 方法提取字符串数据
string dataString = (string)e.Data.GetData(DataFormats.StringFormat);
//使用 BrushConverter 尝试将字符串转换为 Brush
BrushConverter converter = new BrushConverter();
if (converter.IsValid(dataString))
{
Brush newFill = (Brush)converter.ConvertFromString(dataString);
//将画笔应用于提供圆形控件的 UI 的 Ellipse 的 Fill
circleUI.Fill = newFill;
// 判断是否按下ctrl键
if (e.KeyStates.HasFlag(DragDropKeyS
1.2.6 拖放过程中，鼠标进入后显示
/// <summary>
/// 拖放鼠标进入后显示
/// </summary>
/// <param name="e"></param>
protected override void OnDragEnter(DragEventArgs e)
{
base.OnDragEnter(e);
// 用于撤销操作
_previousFill = circleUI.Fill;
// If the DataObject contains string data, extract it.
if (e.Data.GetDataPresent(DataFormats.StringFormat))
{
string dataString = (string)e.Data.GetData(DataFormats.StringFormat);
// If the string can be converted into a Brush, convert it.
BrushConverter converter = new BrushConverter();
if (converter.IsValid(dataString))
{
Brush newFill = (Brush)converter.ConvertFromString(dataString.ToString());
circleUI.Fill = newFill;
}
}
}
1.2.7拖放过程中，鼠标离开后显示
/// <summary>
/// 拖放鼠标进入后显示
/// </summary>
/// <param name="e"></param>
protected override void OnDragEnter(DragEventArgs e)
{
base.OnDragEnter(e);
// 用于撤销操作
_previousFill = circleUI.Fill;
// If the DataObject contains string data, extract it.
if (e.Data.GetDataPresent(DataFormats.StringFormat))
{
string dataString = (string)e.Data.GetData(DataFormats.StringFormat);
// If the string can be converted into a Brush, convert it.
BrushConverter converter = new BrushConverter();
if (converter.IsValid(dataString))
{
Brush newFill = (Brush)converter.ConvertFromString(dataString.ToString());
circleUI.Fill = newFill;
}
}
}
2.拖放具体操作实现
2.1 拖放操作实现UI，主要设置AllowDrop="True"以及设置设置相应的拖放事件
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0"
Background="Beige"
AllowDrop="True"
DragOver="panel_DragOver"
Drop="panel_Drop">
<TextBox Width="Auto" Margin="2"
Text="green"/>
<local:Circle Margin="2" />
<local:Circle Margin="2" />
</StackPanel>
<StackPanel Grid.Column="1"
Background="Bisque"
AllowDrop="True"
DragOver="panel_DragOver"
Drop="panel_Drop">
</StackPanel>
2.2 拖放事件具体实现
2.2.1 拖放过程中鼠标显示形式事件实现
/// <summary>
/// 拖放过程中鼠标的显示形式
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void panel_DragOver(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent("Object"))
{
// These Effects values are used in the drag source's
// GiveFeedback event handler to determine which cursor to display.
if (e.KeyStates == DragDropKeyStates.ControlKey)
{
e.Effects = DragDropEffects.Copy;
}
else
{
e.Effects = DragDropEffects.Move;
}
}
}
2.2.2 拖放操作具体实现
/// <summary>
/// 拖放操作具体实现
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void panel_Drop(object sender, DragEventArgs e)
{
//如果面板中的某个元素已经处理了放置，则面板不应同时处理该放置
if (e.Handled == false)
{
Panel _panel = (Panel)sender;
UIElement _element = (UIElement)e.Data.GetData("Object");
if (_panel != null && _element != null)
{
// 获取元素当前所属的面板，然后将其从该面板中删除，并将其添加到放置它的面板的 Children 中
Panel _parent = (Panel)VisualTreeHelper.GetParent(_element);
if (_parent != null)
{
if (e.KeyStates == DragDropKeyStates.ControlKey &&
e.AllowedEffects.HasFlag(DragDropEffects.Copy))
{
Circle _circle = new Circle((Circle)_element);
标签：控件,circleUI,string,示例,dataString,Brush,拖放,converter From： https://www.cnblogs.com/echo-efun/p/18430902