WPF Thumb控件移动缩放旋转 mvvmlight

WPF Thumb控件是一个非常有用的控件，可以用于实现拖拽、缩放、旋转等功能。在使用mvvmlight框架时，可以将Thumb控件与ViewModel绑定，实现更加优雅的MVVM架构。以下是实现拖拽、缩放、旋转功能的示例代码：

1. 首先，定义一个Thumb控件，并将其与ViewModel绑定：

<Thumb Width="50" Height="50" Canvas.Left="{Binding X}" Canvas.Top="{Binding Y}" 
       Canvas.ZIndex="{Binding ZIndex}" 
       RenderTransformOrigin="0.5,0.5" 
       RenderTransform="{Binding Transform}">
    <!-- 控件内容 -->
</Thumb>

2. 在ViewModel中，定义X、Y、ZIndex、Transform等属性，并在构造函数中初始化：

public class MyViewModel : ViewModelBase
{
    private double x;
    public double X
    {
        get { return x; }
        set { Set(ref x, value); }
    }

    private double y;
    public double Y
    {
        get { return y; }
        set { Set(ref y, value); }
    }

    private int zIndex;
    public int ZIndex
    {
        get { return zIndex; }
        set { Set(ref zIndex, value); }
    }

    private Transform transform;
    public Transform Transform
    {
        get { return transform; }
        set { Set(ref transform, value); }
    }

    public MyViewModel()
    {
        X = 100;
        Y = 100;
        ZIndex = 1;
        Transform = new RotateTransform(0);
    }
}

3. 实现拖拽功能：

private Point startPoint;

public void OnThumbDragStarted(object sender, DragStartedEventArgs e)
{
    startPoint = e.GetPosition(null);
}

public void OnThumbDragDelta(object sender, DragDeltaEventArgs e)
{
    double left = X + e.HorizontalChange;
    double top = Y + e.VerticalChange;

    X = left;
    Y = top;
}

4. 实现缩放功能：

public void OnThumbResizeStarted(object sender, DragStartedEventArgs e)
{
    startPoint = e.GetPosition(null);
}

public void OnThumbResizeDelta(object sender, DragDeltaEventArgs e)
{
    double scaleX = 1 + e.HorizontalChange / Width;
    double scaleY = 1 + e.VerticalChange / Height;

    Transform = new ScaleTransform(scaleX * Transform.Value.M11, scaleY * Transform.Value.M22);
}

5. 实现旋转功能：

public void OnThumbRotateStarted(object sender, DragStartedEventArgs e)
{
    startPoint = e.GetPosition(null);
}

public void OnThumbRotateDelta(object sender, DragDeltaEventArgs e)
{
    Point currentPoint = e.GetPosition(null);
    Vector vector = startPoint - currentPoint;
    double angle = Math.Atan2(vector.Y, vector.X) * 180 / Math.PI;

    Transform = new RotateTransform(angle + Transform.Value.Angle);
}

通过以上代码实现Thumb控件的移动、缩放、旋转功能，可以在WPF应用程序中实现更加优雅的用户界面交互。