在WPF中使用MVVM拖動鼠標時繪制矩形

Question

下面是我的xaml。 我在畫布里面有一個圖像。 我想在圖像上拖動鼠標時在圖像上繪制矩形。 我在WPF中成功完成了它。 但現在我想在MVVM中做到這一點。 我沒有在代碼中使用事件處理程序，而是希望將它們放在我的ViewModel中。 我正在使用MVVM Foundation來實現MVVM。 以下是MVVM Foundation的鏈接。 http://mvvmfoundation.codeplex.com/

任何幫助都非常感謝。

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>

用代碼寫的代碼

// 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;
}

我需要知道在viewmodel中需要寫什么，因此需要在XAML中進行哪些更改。

提前致謝。

Answer 1

請參閱以下鏈接訪問代碼項目！

http://www.codeproject.com/Articles/148503/Simple-Drag-Selection-in-WPF ？

Answer 2

可以在本文/項目中找到實現調整大小的非常簡潔的方法。 如果您使用那里實現的DesignerItemStyle，您可以像這樣添加綁定支持：

<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}">    

這樣就可以在純XAML中調整大小，並使用標准的WPF方法將值傳遞給底層的ViewModel。