.net - MouseEventArgs.GetPosition 在 WPF 中没有按预期工作

Question

我会尝试一点 Shapemoving 并编写以下应用程序:

<Window x:Class="WpfApplication7.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
  <Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="27" />
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <ToolBar Grid.Row="0"/>
    <Canvas Grid.Row="1" MouseDown="OnMouseDown" MouseUp="OnMouseUp" MouseMove="OnMouseMove">
        <Ellipse Width="100" Height="100" Fill="Red" Canvas.Left="50" Canvas.Top="50" />
        <Ellipse Width="100" Height="100" Fill="Red" Canvas.Left="180" Canvas.Top="50" />
        <Rectangle Width="100" Height="100" Fill="Blue" Canvas.Left="220" Canvas.Top="160" />
    </Canvas>
  </Grid>
</Window>

和背后的代码:

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace WpfApplication7
{
  public partial class MainWindow
  {
    private UIElement SelectedObject { get; set; }
    private bool captureMouse;
    private Point diffPosition;

    public MainWindow()
    {
        InitializeComponent();
    }

    private void OnMouseDown(object sender, MouseButtonEventArgs e)
    {
        SelectedObject = e.Source as UIElement;
        if (SelectedObject != null)
        {
            captureMouse = SelectedObject.CaptureMouse();
            diffPosition = e.GetPosition(SelectedObject);
        }
    }

    private void OnMouseUp(object sender, MouseButtonEventArgs e)
    {
        if (captureMouse)
        {
            SelectedObject.ReleaseMouseCapture();
        }
        SelectedObject = null;
    }

    private void OnMouseMove(object sender, MouseEventArgs e)
    {
        if (SelectedObject != null)
        {
            Canvas.SetLeft(SelectedObject, e.GetPosition(this).X - diffPosition.X);
            Canvas.SetTop(SelectedObject, e.GetPosition(this).Y - diffPosition.Y);
        }
    }
  }
}

我想在 OnMouseDown 中使用 GetPosition 相对于 SelectedObject 获取点击点的 diffPosition 拯救我几行代码，但增加了工具栏的高度。所以我的 Y 坐标比我预期的多 27 个像素。如果我删除工具栏，一切正常。我需要做什么才能使表单中的工具栏获得正确的偏移量？

我知道这只是一个小错误，但我找不到。

Answer 1

命名您的绘图区域:

 <Canvas Grid.Row="1" x:Name="drawingArea" ...>
    ...
 </Canvas>

并将位置与 drawingArea 的进行比较。

e.GetPosition(this.drawingArea)

这样你就不用担心布局变化等问题