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Philippe
Asked:2020-07-04 17:58:26 +0000 UTC2020-07-04 17:58:26 +0000 UTC

单击 WPF 窗口绘制按钮

  • 772

我想做一个应用：用户点击并按住鼠标，当他松开鼠标时，绘制Button左上角是点击（事件MouseDown）的坐标，右下角是事件的坐标用户释放鼠标按钮的地方（事件MouseUp）。这是代码MouseDown：

private void MainWindow_MouseDown(object sender, MouseButtonEventArgs e)
{
    StartPoint = e.GetPosition(this);
    //Свойство StartPoint объявляется сверху таким образом
    //private System.Windows.Point StartPoint { get; set; }
}

这是代码MouseUp：

private void MainWindow_MouseUp(object sender, MouseButtonEventArgs e)
{
     EndPoint = e.GetPosition(this);
     //Свойство EndPoint объявляется сверху таким образом
     //private System.Windows.Point EndPoint { get; set; }

     Button temp = new Button();
     temp.Margin = new Thickness(StartPoint.X, StartPoint.Y, EndPoint.X, EndPoint.Y);
     temp.Background = new SolidColorBrush(Colors.Blue);
     temp.Content = "Do not click me!";

     mainGrid.Children.Add(temp);
}

它不起作用，按钮绘制太大或根本不绘制。我做错了什么，我怎样才能让它发挥作用？

c#

3 个回答

  1. Best Answer
    1. 必须为放置按钮的控件计算坐标。在这种情况下，对于网格。
    2. 右侧和底部的边距不是坐标，它是从控件边缘到按钮边缘的距离（在您的情况下）

    稍微重写你的代码

    private void MainWindow_MouseDown(object sender, MouseButtonEventArgs e)
{
    StartPoint = e.GetPosition(mainGrid);
    //Свойство StartPoint объявляется сверху таким образом
    //private System.Windows.Point StartPoint { get; set; }
}

private void MainWindow_MouseUp(object sender, MouseButtonEventArgs e)
{
    EndPoint = e.GetPosition(mainGrid);
    //Свойство EndPoint объявляется сверху таким образом
    //private System.Windows.Point EndPoint { get; set; }           

    Button temp = new Button();
    temp.Margin = new Thickness(StartPoint.X, StartPoint.Y, mainGrid.ActualWidth - EndPoint.X, mainGrid.ActualHeight - EndPoint.Y);
    temp.Background = new SolidColorBrush(Colors.Blue);
    temp.Content = "Do not click me!";

    mainGrid.Children.Add(temp);
}
    • 4

  2. 为了通过绝对坐标定位控件，使用是正确的Canvas，它是专门为此设计的。所以我会这样写：

    XAML：

    <Grid>
    <Canvas MouseLeftButtonDown="OnCanvasLeftMouseDown" Background="Transparent"/>
</Grid>

    代码隐藏：

    void OnCanvasLeftMouseDown(object sender, MouseButtonEventArgs eDown)
{
    var canvas = (Canvas)sender;
    var startPos = eDown.GetPosition(canvas);
    canvas.MouseLeftButtonUp += OnUp;
    void OnUp(object _, MouseButtonEventArgs eUp) // захватим позицию начала
    {
        canvas.MouseLeftButtonUp -= OnUp;
        var endPos = eUp.GetPosition(canvas);
        var button = new Button()
        {
            Content = "Do not click me!",
            Width = Math.Abs(endPos.X - startPos.X),
            Height = Math.Abs(endPos.Y - startPos.Y)
        };
        Canvas.SetLeft(button, Math.Min(startPos.X, endPos.X));
        Canvas.SetTop(button, Math.Min(startPos.Y, endPos.Y));
        canvas.Children.Add(button);
    }
}

    来自@tym32167，更严格的版本：

    void OnCanvasLeftMouseDown(object sender, MouseButtonEventArgs eDown)
{
    var canvas = (Canvas)sender;
    var startPos = eDown.GetPosition(canvas);
    canvas.MouseLeftButtonUp += OnUp;
    canvas.Unloaded += Unsubscribe;
    Mouse.Capture(canvas);

    void OnUp(object _, MouseButtonEventArgs eUp) // захватим позицию начала
    {
        Mouse.Capture(null);
        Unsubscribe(_, eUp);
        var endPos = eUp.GetPosition(canvas);
        if (!canvas.IsMouseOver)
            return;
        var button = new Button()
        {
            Content = "Do not click me!",
            Width = Math.Abs(endPos.X - startPos.X),
            Height = Math.Abs(endPos.Y - startPos.Y)
        };
        Canvas.SetLeft(button, Math.Min(startPos.X, endPos.X));
        Canvas.SetTop(button, Math.Min(startPos.Y, endPos.Y));
        canvas.Children.Add(button);
    }

    void Unsubscribe(object _, RoutedEventArgs e)
    {
        canvas.MouseLeftButtonUp -= OnUp;
        canvas.Unloaded -= Unsubscribe;
    }
}

    添加了鼠标捕获，以便鼠标释放发生在同一上下文中。还添加了一个卸载 'a 的订阅Canvas，以防 UI 逻辑在释放鼠标之前卸载它。

    • 2 
  3. private void Grid_PreviewMouseDown(object sender, MouseButtonEventArgs e) {
    Mouse.Capture(sender as IInputElement);
}

private void Grid_PreviewMouseUp(object sender, MouseButtonEventArgs e) {

    Point upPoint = e.GetPosition(sender as Grid);

    if (upPoint.X < 0 || upPoint.X > mainGrid.ActualWidth ||
            upPoint.Y < 0 || upPoint.Y > mainGrid.ActualHeight)
        return;

    Mouse.Capture(null);

    Button button = new Button();
    button.Margin = new Thickness(upPoint.X, upPoint.Y, 0, 0);
    button.VerticalAlignment = VerticalAlignment.Top;
    button.HorizontalAlignment = HorizontalAlignment.Left;
    button.Background = new SolidColorBrush(Colors.Blue);
    button.Content = "Do not click me!";
    button.Width = 120;
    button.Height = 20;
    mainGrid.Children.Add(button);
}
    • 0

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