Question

我的WPF测试应用程序中有以下XAML代码：

<Canvas x:Name="canvas"
       HorizontalAlignment="Stretch" VerticalAlignment="Stretch"
       Background="CornflowerBlue" MouseMove="canvas_MouseMove"
       MouseLeftButtonUp="canvas_MouseLeftButtonUp"
/>

在我的.cs文件中：

private const int Radius = 10;
private Ellipse _prev;

private void canvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    if (this._prev != null)
        canvas.Children.Remove(this._prev);
    var pos = e.GetPosition(canvas);
    var c = new Ellipse()
    {
        Height = 2 * Radius,
        Width = 2 * Radius,
        Fill = new SolidColorBrush(Color.FromArgb(255, 255, 0, 0)),
    };
    double x = pos.X - Radius;
    double y = pos.Y - Radius;
    Canvas.SetTop(c, y);
    Canvas.SetLeft(c, x);
    canvas.Children.Add(c);
}

private void canvas_MouseMove(object sender, MouseEventArgs e)
{
    if(e.LeftButton == MouseButtonState.Pressed)
    {
        if (this._prev != null)
            canvas.Children.Remove(this._prev);
        var pos = e.GetPosition(canvas);
        _prev = new Ellipse()
        {
            Height = 2 * Radius,
            Width = 2 * Radius,
            Fill = new SolidColorBrush(Color.FromArgb(100, 255, 0, 0)),
        };
        double x = pos.X - Radius;
        double y = pos.Y - Radius;
        Canvas.SetTop(_prev, y);
        Canvas.SetLeft(_prev, x);
        canvas.Children.Add(_prev);
    }
}

我想要做的基本上是当用户点击鼠标左键并拖动时，光标后面会出现一个带有一点alpha字母的红色圆圈。当用户释放鼠标时，红色圆圈停留在那里，没有更多的alpha着色。看起来像一个非常简单的任务，但MouseLeftButtonUp事件仅在我释放它之前不拖动鼠标时触发。我在这里做错了什么？

Answer 1

您总是在canvas_MouseMove函数中删除并添加椭圆到画布。如果你尝试在canvas_MouseMove中改变椭圆的位置，你可以做你想做的事情

同时使用MouseMove时，C＃WPF MouseLeftButtonUp事件不会触发

1 个答案: