如何在WPF中拖动画布上的按钮[重复]

Question

过去几天我一直在试图弄清楚如何在 C# 的 WPF 中使用 DragDrop 功能，这样我就可以创建一个按钮并在画布中拖动它。我想我错过了一些东西，但经过努力研究后，我无法弄清楚它是什么。我需要做的就是在画布中拖动按钮。

这是我的 XAML 代码：

x:Class="DragDrop_Test.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:DragDrop_Test"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">

    <Canvas Name="MyCanvas" Width = "300" Height= "200" Background="WhiteSmoke" Margin= "10, 0,190,100" AllowDrop="True" Drop="Canvas_Drop">
        <Button Name="btn" Content="Button1" MouseMove="btn_MouseMove" PreviewMouseLeftButtonDown="btn_PreviewMouseLeftButtonDown">

        </Button>
    </Canvas>


</Window>

这是我的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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.Navigation;
using System.Windows.Shapes;

namespace DragDrop_Test
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Control draggedItem;
        bool IsDragging;
        public MainWindow()
        {
            InitializeComponent();
            IsDragging = false;
        }


        private void Canvas_Drop(object sender, DragEventArgs e)
        {
            if (!IsDragging)
                return;

            IsDragging = false;
        }



        private void btn_MouseMove(object sender, MouseEventArgs e)
        {
            var dependencyObject = (Button)sender;
            draggedItem = dependencyObject;

            if (!IsDragging) 
                return;
            if (dependencyObject != null && dependencyObject.IsMouseOver)
            {
                DragDrop.DoDragDrop(dependencyObject, dependencyObject, DragDropEffects.Move);
            }
        }

        private void btn_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            IsDragging = true;
            draggedItem = (Button)sender;
        }
    }
}

提前致谢

Answer 1

如果我理解正确，“拖放”不是您所需要的。它是一种数据传输方法，而不是位置设置器。根据msdn：

拖放通常是指一种数据传输的方法 涉及使用鼠标（或其他一些指点设备）选择一个 或更多对象，将这些对象拖到某个所需的放置目标上 在用户界面 (UI) 中，并删除它们

如果您只想移动按钮，您可以尝试使用Canvas.SetTop/Canvas.SetLeft 或TranslateTransform。可能是这样的：

public partial class MainWindow : Window
    {
        Control draggedItem;
        Point itemRelativePosition;
        bool IsDragging;
        public MainWindow()
        {
            InitializeComponent();
            IsDragging = false;
        }

        private void btn_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            IsDragging = true;
            draggedItem = (Button)sender;
            itemRelativePosition = e.GetPosition(draggedItem);
        }

        private void btn_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if (!IsDragging)
                return;

            IsDragging = false;
        }

        private void btn_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            if (!IsDragging)
                return;

            Point canvasRelativePosition = e.GetPosition(MyCanvas);

            Canvas.SetTop(draggedItem, canvasRelativePosition.Y - itemRelativePosition.Y);
            Canvas.SetLeft(draggedItem, canvasRelativePosition.X - itemRelativePosition.X);
        }
    }