WPF:如何画一个圆并拖动它?

“不管它是什么”很重要,因为WPF中元素的放置高度依赖于父容器。

有一篇代码项目文章描述了如何在Canvas中拖动元素: Dragging Elements in a Canvas

如果你只想移动那个圆圈,而不想移动现有画布/网格中的其他控件;我建议你使用DragCanvas(来自文章)作为普通Canvas/Grid的覆盖层。

<Canvas Background="White" Name="canvas" Width="950" Height="500" MouseDown="MouseMove">
    <Ellipse Name="bola" Canvas.Left="130" Canvas.Top="79" Width="50" Height="50" Fill="Green"  />
</Canvas>

MouseDown="MouseMoveFunction" 。每当您单击画布时,都会调用该事件处理程序。如果你想让它随着鼠标的移动而移动,请使用 MouseMove="MouseMoveFunction"

然后,每次移动鼠标时,只需更新椭圆的位置。以下代码位于鼠标事件时调用的函数中:

    private void MouseMove(object sender, MouseEventArgs e)
    {
        Point punto = e.GetPosition(canvas);
        int mouseX = (int)punto.X;
        int mouseY = (int)punto.Y;
        bola.SetValue(Canvas.LeftProperty, (double)mouseX); //set x
        bola.SetValue(Canvas.TopProperty, (double)mouseY); //set y

    }

我复制了下面的代码,所以你可以复制它。

<Window x:Class="WPFExample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WPFExample"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525" Background="LightGray">
    <Grid>
        <Canvas HorizontalAlignment="Left" Name="MainCanvas"
                Height="300" Width="500" Margin="5,5,5,5" VerticalAlignment="Top" Background="LightYellow" MouseDown="Canvas_MouseDown" MouseMove="MainCanvas_MouseMove"
                />
        <Ellipse Name="post" Width="50" Height="50" Fill="Red" Margin="5,5,5,5"  />

    </Grid>
</Window>

接下来,将代码添加到主窗体中:

       private void Draw(Point m)
        {
            MainCanvas.Children.Clear();

            int mX = (int)m.X;
            int mY = (int)m.Y;
            Ellipse el = new Ellipse();
            el.Width = 15;
            el.Height = 15;
            el.SetValue(Canvas.LeftProperty, (Double)mX);
            el.SetValue(Canvas.TopProperty, (Double)mY);
            el.Fill = Brushes.Black;

            MainCanvas.Children.Add(el);
        }

        private void Canvas_MouseDown(object sender, MouseButtonEventArgs e)
        {
            Draw(e.GetPosition(MainCanvas));
        }

        private void MainCanvas_MouseMove(object sender, MouseEventArgs e)
        {
            Draw(e.GetPosition(MainCanvas));
        }

这是该应用程序的快照——当你运行它并移动鼠标时,无论你在哪里移动鼠标,黑色圆圈都会被重新绘制,就像你在拖动它一样。

我有一篇关于在WPF环境中使用MVVM架构拖放矩形的示例博客文章。内容太长,无法在这里复制,但说明应该相当简单。

drag and drop rectangle in WPF / MVVM