Question

我想制作一个用鼠标移动和缩放儿童的观察器。所以，我创建了类TransformViewer : UserControl并覆盖了一个事件方法。但是OnMouseMove有问题。当我翻译RenderTransform时，即使我不移动鼠标，也会连续调用OnMouseMove。并且RenderTransform震动。

protected override void OnMouseMove(MouseEventArgs e) {
        Point mouse = e.GetPosition( this );
        Vector delta = Point.Subtract( mouse, oldMouse );
        oldMouse = mouse;

        if(Keyboard.IsKeyDown( Key.LeftShift ) &&
            (e.LeftButton == MouseButtonState.Pressed || e.RightButton == MouseButtonState.Pressed)) {
            Matrix matrix = transform.Matrix;
            matrix.Translate( delta.X, delta.Y );
            transform.Matrix = matrix;

            e.Handled = true;
            RenderTransform = transform;
        }

    }

为什么会这样？

Answer 1

最好更改孩子的RenderTransform。

public class TransformViewer : UserControl {

    private readonly MatrixTransform transform = new MatrixTransform();
    private Point pressedMouse;


    protected override void OnMouseDown(MouseButtonEventArgs e) {
        pressedMouse = transform.Inverse.Transform( e.GetPosition( this ) );
    }


    protected override void OnMouseMove(MouseEventArgs e) {
        if(e.MiddleButton == MouseButtonState.Pressed) {
            Point mouse = transform.Inverse.Transform( e.GetPosition( this ) );
            Vector delta = Point.Subtract( mouse, pressedMouse ); // delta from old mouse to current mouse
            var translate = new TranslateTransform( delta.X, delta.Y );
            transform.Matrix = translate.Value * transform.Matrix;

            ((UIElement) Content).RenderTransform = transform;
            e.Handled = true;
        }
    }


    protected override void OnMouseWheel(MouseWheelEventArgs e) {
            float scale = 1.1f;
            if(e.Delta < 0) scale = 1f / scale;
            Point mouse = e.GetPosition( this );

            Matrix matrix = transform.Matrix;
            matrix.ScaleAt( scale, scale, mouse.X, mouse.Y );
            transform.Matrix = matrix;

            ((UIElement) Content).RenderTransform = transform;
            e.Handled = true;
    }

}

如何在WPF中使用鼠标拖动RenderTransform？

1 个答案: