C＃WPF - 拖动图像

Question

我试图获得一些简单的功能，从文件中获取图像，将其添加到Canvas，然后允许用户左键单击（并保持）图像，然后将其拖动到Canvas（即更新图像的位置）

这是我到目前为止，我应该添加什么？

private void btnAddImage_Click(object sender, RoutedEventArgs e) {
    try {
        System.Windows.Forms.OpenFileDialog open = new System.Windows.Forms.OpenFileDialog();
        open.Filter = "Image Files(*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp";
        if (open.ShowDialog() == System.Windows.Forms.DialogResult.OK) {
            PictureBox PictureBox1 = new PictureBox();
            PictureBox1.Image = new Bitmap(open.FileName);
            myCanvas.children.add(PictureBox1);
        }
    }
    catch (Exception) { throw new ApplicationException("Failed loading image"); }
}

Answer 1

您可以将“ 图像”控件添加到“画布”，并在鼠标输入上修改其“ Left和“ Top属性。

XAML：

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <Canvas x:Name="canvas"
            MouseLeftButtonDown="CanvasMouseLeftButtonDown"
            MouseLeftButtonUp="CanvasMouseLeftButtonUp"
            MouseMove="CanvasMouseMove"/>
    <Button Grid.Row="1" Content="Add Image" Click="AddButtonClick"/>
</Grid>

代码背后：

private void AddButtonClick(object sender, RoutedEventArgs e)
{
    var dialog = new Microsoft.Win32.OpenFileDialog();
    dialog.Filter =
        "Image Files (*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp";

    if ((bool)dialog.ShowDialog())
    {
        var bitmap = new BitmapImage(new Uri(dialog.FileName));
        var image = new Image { Source = bitmap };
        Canvas.SetLeft(image, 0);
        Canvas.SetTop(image, 0);
        canvas.Children.Add(image);
    }
}

private Image draggedImage;
private Point mousePosition;

private void CanvasMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    var image = e.Source as Image;

    if (image != null && canvas.CaptureMouse())
    {
        mousePosition = e.GetPosition(canvas);
        draggedImage = image;
        Panel.SetZIndex(draggedImage, 1); // in case of multiple images
    }
}

private void CanvasMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    if (draggedImage != null)
    {
        canvas.ReleaseMouseCapture();
        Panel.SetZIndex(draggedImage, 0);
        draggedImage = null;
    }
}

private void CanvasMouseMove(object sender, MouseEventArgs e)
{
    if (draggedImage != null)
    {
        var position = e.GetPosition(canvas);
        var offset = position - mousePosition;
        mousePosition = position;
        Canvas.SetLeft(draggedImage, Canvas.GetLeft(draggedImage) + offset.X);
        Canvas.SetTop(draggedImage, Canvas.GetTop(draggedImage) + offset.Y);
    }
}

Answer 2

您需要在代码中添加拖放支持，方法是在您使用的WPF控件中处理拖放路由事件。

如果您使用的是.NET 4.0及更高版本（Visual Studio 2010及更高版本），请参阅此WPDN拖放概述的 MSDN库。

但请注意拖放的数据类型。