即使光标在画布之外，也会调用MouseMobile事件。画布周围的“边界”不起作用

Question

对未来情况的简要描述：

当鼠标在画布上移动时，我希望在画布上显示一个椭圆。椭圆应该一直跟随鼠标移动，直到用户点击鼠标左键。当用户点击鼠标左键时，程序会将椭圆放置在画布上。

因此，我使用了以下xaml代码：

    <Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="700" Width="1200">



<Grid>
    <Border ClipToBounds="true">
    <Canvas x:Name="canvasss" Background="AntiqueWhite" Width="524" Height="368" MouseMove="Canvasss_MouseMove" MouseDown="Canvasss_MouseDown">

    </Canvas>
    </Border>
</Grid>

和c#代码：

    using System.Collections.Generic;
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Input;
    using System.Windows.Media;
    using System.Windows.Shapes;

    namespace WpfApplication1
    {
         public class Item
         {
            private readonly Ellipse shape;

            public Item(Canvas canvas)
            {
                shape = new Ellipse { Width = 50, Height = 50, Fill = Brushes.Black };
                canvas.Children.Add(shape);
                SetPosition(0.0, 0.0);
            }

            public void SetPosition(double x, double y)
            {
                Canvas.SetLeft(shape, x);
                Canvas.SetTop(shape, y);
            }
        }

        public partial class MainWindow : Window
        {
            private readonly IList<Item> shapes;
            private Item currentMovingShape;

            public MainWindow()
            {
                InitializeComponent();
                shapes = new List<Item>();
                InitMovingShape();
            }

            private void InitMovingShape()
            {
                currentMovingShape = new Item(canvasss);
            }

            private void SetMovingShapePosition(MouseEventArgs e)
            {
                var pos = e.GetPosition(canvasss);
                currentMovingShape.SetPosition(pos.X - 25, pos.Y - 25);
            }

            private void Canvasss_MouseMove(object sender, MouseEventArgs e)
            {
                var pos = e.GetPosition(canvasss);
                currentMovingShape.SetPosition(pos.X - 25, pos.Y - 25);
            }

            private void Canvasss_MouseDown(object sender, MouseButtonEventArgs e)
            {
                shapes.Add(currentMovingShape);
                InitMovingShape();            
            }


         }
    }

问题是，一旦鼠标离开画布，椭圆仍然会粘在鼠标上，甚至可以将椭圆放置在画布之外。

首先，我使用了代码（代码来自stijn： C#-WPF-画布上的Mousemove事件会重载鼠标事件，因此不会触发单击事件），而没有在xaml代码中的画布周围的边界。然后我读到在画布周围放置一个边界可能会有所帮助（即使光标在画布之外也会调用MouseMobile事件）并将其实现到您可以看到的xaml代码中。不幸的是，它没有帮助。

有人能帮我解决吗？我非常欣赏代码解决方案，因为我是c#的初学者。

Answer 1

看起来您想在控件中实现装饰器。一定要阅读它们，因为它们将方便地在wpf中轻松执行这些操作。

但是，要解决您的问题。您应该在代码中实现MouseEnter和MouseLeave事件。在MouseEnter上添加形状，然后在MouseLeave或MouseDown上删除形状。因此，当鼠标重新进入画布时，MouseEnter逻辑将启动并添加形状，您的MouseMove逻辑将使用鼠标移动形状。希望我在这里说清楚。如果您仍在与代码斗争，请告诉我。

编辑

xaml

<Grid Background="Transparent">
        <Canvas x:Name="canvasss" Background="AntiqueWhite" Width="300" Height="300"  MouseEnter="canvasss_MouseEnter" MouseLeave="canvasss_MouseLeave"  MouseMove="Canvasss_MouseMove" MouseDown="Canvasss_MouseDown" Margin="50" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Grid>

密码

public partial class MainWindow : Window
    {
        private readonly IList<Ellipse> shapes;
        private Ellipse currentMovingShape;
        public MainWindow()
        {
            InitializeComponent();
            shapes = new List<Ellipse>();
        }

        private void canvasss_MouseEnter(object sender, MouseEventArgs e)
        {
            AddEllipse();
        }

        private void AddEllipse()
        {
            currentMovingShape = new Ellipse { Width = 50, Height = 50, Fill = Brushes.Black };
            currentMovingShape.IsHitTestVisible = false;
            canvasss.Children.Add(currentMovingShape);
            Canvas.SetLeft(currentMovingShape, Mouse.GetPosition(canvasss).X - 25);
            Canvas.SetTop(currentMovingShape, Mouse.GetPosition(canvasss).Y - 25);
        }

        private void canvasss_MouseLeave(object sender, MouseEventArgs e)
        {
            if (currentMovingShape != null)
            {
                canvasss.Children.Remove(currentMovingShape);
                currentMovingShape = null;
            }
        }
        private void Canvasss_MouseMove(object sender, MouseEventArgs e)
        {
            Canvas.SetLeft(currentMovingShape, e.GetPosition(canvasss).X - 25);
            Canvas.SetTop(currentMovingShape, e.GetPosition(canvasss).Y - 25);
        }

        private void Canvasss_MouseDown(object sender, MouseButtonEventArgs e)
        {
            if (currentMovingShape != null)
            {
                currentMovingShape.IsHitTestVisible = true;
                shapes.Add(currentMovingShape);
                AddEllipse();
            }

        }
    }