在WPF中使用MVVM拖动鼠标时绘制矩形 [英] Draw rectangle when mouse dragged using MVVM in WPF

问题描述

下面是我的xaml.我在画布中有一个图像.我想在图像上拖动鼠标时在图像上绘制矩形.我在 WPF 中成功做到了.但现在我想在 MVVM 中做到这一点.我希望在我的 ViewModel 中拥有它们，而不是在后面的代码中包含事件处理程序.我正在使用 MVVM Foundation 来实现 MVVM.以下是 MVVM 基金会的链接.http://mvvmfoundation.codeplex.com/

Below is my xaml. I have an image inside a canvas. I want to draw rectangle on the image when mouse is dragged on the image. I did it successfully in WPF. But now I want to do it in MVVM. Instead of having the event handlers in code behind I want to have them in my ViewModel. I am using MVVM Foundation for implementing MVVM. Below is a link to MVVM Foundation. http://mvvmfoundation.codeplex.com/

非常感谢任何帮助.

XAML

<Canvas Name="cnvImage">
        <Image Height="348" HorizontalAlignment="Left" Margin="12,39,0,0" Name="imgPreview" 
               Stretch="Fill" VerticalAlignment="Top" Width="443" 
               Source="/Images/CapturedImage.png" 
                MouseDown="imgCamera_MouseDown" MouseMove="imgCamera_MouseMove" MouseUp="imgCamera_MouseUp" />
    </Canvas>

代码写在后面

// This is the rectangle to be shown when mouse is dragged on camera image.
private Point startPoint;
private Rectangle rectSelectArea;


/// <summary>
/// 
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void imgCamera_MouseDown(object sender, MouseButtonEventArgs e)
{
    startPoint = e.GetPosition(cnvImage);

    // Remove the drawn rectanglke if any.
    // At a time only one rectangle should be there
    if (rectSelectArea != null)
        cnvImage.Children.Remove(rectSelectArea);

    // Initialize the rectangle.
    // Set border color and width
    rectSelectArea = new Rectangle
    {
        Stroke = Brushes.LightBlue,
        StrokeThickness = 2
    };

    Canvas.SetLeft(rectSelectArea, startPoint.X);
    Canvas.SetTop(rectSelectArea, startPoint.X);
    cnvImage.Children.Add(rectSelectArea);
}

/// <summary>
/// 
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void imgCamera_MouseMove(object sender, MouseEventArgs e)
{
    if (e.LeftButton == MouseButtonState.Released || rectSelectArea == null)
        return;

    var pos = e.GetPosition(cnvImage);

    // Set the position of rectangle
    var x = Math.Min(pos.X, startPoint.X);
    var y = Math.Min(pos.Y, startPoint.Y);

    // Set the dimenssion of the rectangle
    var w = Math.Max(pos.X, startPoint.X) - x;
    var h = Math.Max(pos.Y, startPoint.Y) - y;

    rectSelectArea.Width = w;
    rectSelectArea.Height = h;

    Canvas.SetLeft(rectSelectArea, x);
    Canvas.SetTop(rectSelectArea, y);
}

/// <summary>
/// 
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void imgCamera_MouseUp(object sender, MouseButtonEventArgs e)
{
    rectSelectArea = null;
}

我需要知道我需要在我的视图模型中写什么，以及相应地在 XAML 中需要哪些更改.

I need to know what do I need to write in my viewmodel and accordingly what changes are required in XAML.

提前致谢.

推荐答案

可以在 这篇文章/项目.如果您使用在那里实现的 DesignerItemStyle，您可以像这样添加绑定支持:

A very neat way of implementing resizing can be found in this article / project. If you use the DesignerItemStyle implemented there, you can add binding support like so :

<Rectangle Style="{StaticResource DesignerItemStyle}"
           Canvas.Left="{Binding Path=Leftoffset, Mode=TwoWay}"
           Canvas.Top="{Binding Path=Topoffset, Mode=TwoWay}"
           Width="{Binding Path=Width, Mode=TwoWay}"
           Height="{Binding Path=Height, Mode=TwoWay}">    

这留下了在纯 XAML 中调整内容大小的阻力，并使用标准 WPF 方法将值获取到基础 ViewModel.

That leaves the drag to resize stuff in pure XAML and uses standard WPF means to get the values to the underlying ViewModels.

这篇关于在WPF中使用MVVM拖动鼠标时绘制矩形的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！