我有一个简单的程序，它实现了这个问题中讨论的代码来跟踪鼠标移动。但是，似乎只有在设置 Canvas 控件的背景颜色时才会触发事件。
XAML（设置了背景颜色）：
<Window x:Class="SimplePaint.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="501" Width="784">
<Grid>
<Canvas Height="402" HorizontalAlignment="Left" Margin="12,12,0,0" Name="PaintCanvas" VerticalAlignment="Top" Width="738" MouseDown="PaintCanvas_MouseDown" MouseMove="PaintCanvas_MouseMove" MouseUp="PaintCanvas_MouseUp" Background="#FFDEF4FF">
<Polyline x:Name="polyline" Stroke="Black" StrokeThickness="3"/>
</Canvas>
</Grid>
</Window>
C＃：
private bool drawing = false;
private void PaintCanvas_MouseDown(object sender, MouseButtonEventArgs e)
{
this.drawing = true;
}
private void PaintCanvas_MouseMove(object sender, MouseEventArgs e)
{
if (this.drawing)
polyline.Points.Add(e.GetPosition(this.PaintCanvas));
}
private void PaintCanvas_MouseUp(object sender, MouseButtonEventArgs e)
{
this.drawing = false;
}
此代码有效。但是，如果我Background="#FFDEF4FF"从 XAML 中删除，则在使用该程序时不会发生任何事情。在事件处理程序中设置断点表明它们不会触发。