wpf mvvmlight 实现鼠标拖拽改变rectangle大小以及旋转

要实现鼠标拖拽改变Rectangle大小以及旋转，可以使用WPF的MVVMLight框架来实现。

首先，在ViewModel中定义Rectangle的位置、大小和角度等属性，以及鼠标拖拽的事件处理函数。

public class MainViewModel : ViewModelBase
{
    private double _left;
    private double _top;
    private double _width;
    private double _height;
    private double _angle;

    public double Left
    {
        get { return _left; }
        set { Set(ref _left, value); }
    }

    public double Top
    {
        get { return _top; }
        set { Set(ref _top, value); }
    }

    public double Width
    {
        get { return _width; }
        set { Set(ref _width, value); }
    }

    public double Height
    {
        get { return _height; }
        set { Set(ref _height, value); }
    }

    public double Angle
    {
        get { return _angle; }
        set { Set(ref _angle, value); }
    }

    public void OnMouseDown(object sender, MouseButtonEventArgs e)
    {
        // 鼠标按下时记录鼠标位置
    }

    public void OnMouseMove(object sender, MouseEventArgs e)
    {
        // 鼠标移动时根据鼠标位置计算Rectangle的位置、大小和角度
    }

    public void OnMouseUp(object sender, MouseButtonEventArgs e)
    {
        // 鼠标抬起时清空鼠标位置记录
    }
}

接着，在View中使用MVVMLight框架提供的Binding绑定属性和事件处理函数。

<Window.DataContext>
    <vm:MainViewModel />
</Window.DataContext>
<Grid>
    <Rectangle Fill="Blue" Width="{Binding Width}" Height="{Binding Height}"
               Canvas.Left="{Binding Left}" Canvas.Top="{Binding Top}"
               RenderTransformOrigin="0.5,0.5">
        <Rectangle.RenderTransform>
            <RotateTransform Angle="{Binding Angle}" />
        </Rectangle.RenderTransform>
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="MouseDown">
                <i:InvokeCommandAction Command="{Binding MouseDownCommand}" />
            </i:EventTrigger>
            <i:EventTrigger EventName="MouseMove">
                <i:InvokeCommandAction Command="{Binding MouseMoveCommand}" />
            </i:EventTrigger>
            <i:EventTrigger EventName="MouseUp">
                <i:InvokeCommandAction Command="{Binding MouseUpCommand}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </Rectangle>
</Grid>

最后，在ViewModel中实现鼠标拖拽事件处理函数，计算Rectangle的位置、大小和角度。

public RelayCommand MouseDownCommand { get; private set; }
public RelayCommand MouseMoveCommand { get; private set; }
public RelayCommand MouseUpCommand { get; private set; }

public MainViewModel()
{
    MouseDownCommand = new RelayCommand(OnMouseDown);
    MouseMoveCommand = new RelayCommand(OnMouseMove);
    MouseUpCommand = new RelayCommand(OnMouseUp);
}

private Point _lastMousePosition;

public void OnMouseDown()
{
    _lastMousePosition = Mouse.GetPosition(Application.Current.MainWindow);
}

public void OnMouseMove()
{
    if (Mouse.LeftButton == MouseButtonState.Pressed)
    {
        var currentMousePosition = Mouse.GetPosition(Application.Current.MainWindow);
        var delta = currentMousePosition - _lastMousePosition;
        _lastMousePosition = currentMousePosition;

        // 计算Rectangle的位置、大小和角度
    }
}

public void OnMouseUp()
{
    _lastMousePosition = new Point();
}

这样就可以通过MVVMLight框架实现鼠标拖拽改变Rectangle大小以及旋转了。