c# - 即使光标在 Canvas 之外，也会调用 MouseMove 事件

Question

我不知道我的代码或 WPF 是否有问题，但问题是:我想创建一个小程序，您可以在其中使用光标在 Canvas 中绘图。我有一个简单的 WPF 窗口:

<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="475" Width="544">
<Grid>    
    <Grid.RowDefinitions>
        <RowDefinition Height="100px"></RowDefinition>
        <RowDefinition Height ="*"></RowDefinition>
        <RowDefinition Height="100px"></RowDefinition>
    </Grid.RowDefinitions>    
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="100px"></ColumnDefinition>
        <ColumnDefinition Width="*"></ColumnDefinition>
        <ColumnDefinition Width="100px"></ColumnDefinition>
    </Grid.ColumnDefinitions>
        <Canvas Grid.Row="1" Grid.Column="1"  Name="imageCanvas" MouseEnter="StackPanel_MouseEnter" MouseLeave="StackPanel_MouseLeave" Background="LightGray" 
                      MouseDown="StackPan_MouseDown" MouseUp="StackPan_MouseUp" MouseMove="StackPan_MouseMove">

        </Canvas>        
</Grid>

这里是后台代码:

   private void StackPan_MouseDown(object sender, MouseButtonEventArgs e)
    {
        draw = true;
    }

    private void StackPan_MouseUp(object sender, MouseButtonEventArgs e)
    {
        draw = false;
    }

    private void StackPan_MouseMove(object sender, MouseEventArgs e)
    {
        if (draw)
        {
            var pos = Mouse.GetPosition(imageCanvas);
            Rectangle rec = new Rectangle()
                    {
                        Width = 10,
                        Height = 10,
                        Fill = Brushes.Red,
                    };
            Canvas.SetTop(rec, pos.Y);
            Canvas.SetLeft(rec, pos.X);
            imageCanvas.Children.Add(rec);
        }

    }

我能做的是: https://www.dropbox.com/s/7moq4p8f8f409b3/wpf_canvas.png

为什么当光标在 Canvas 之外时调用 StackPan_MouseMove？

这是可执行文件，您可以在其中注意到此行为: https://www.dropbox.com/s/ye1w2j9chld2oif/WpfApplication1.exe

Answer 1

尝试将 Canvas 放在 Border 控件中并设置 Border 控件的 ClipToBounds属性为 true。

<Border ClipToBounds="true" Grid.Row="1" Grid.Column="1" >
    <Canvas Name="imageCanvas" MouseEnter="StackPanel_MouseEnter" MouseLeave="StackPanel_MouseLeave" Background="LightGray" 
            MouseDown="StackPan_MouseDown" MouseUp="StackPan_MouseUp" MouseMove="StackPan_MouseMove">
    </Canvas>
</Border>

稍微不同的是，似乎 InkPresenter/InkCanvas除非您出于特定原因避免使用它们，否则可能更适合您尝试执行的操作。