Xamarin 叠加视图中的椭圆形

Question

我按照这个Blog 在我的相机预览中添加了叠加视图。

在后台打开Camera Preview，在它的顶部有覆盖的外部矩形（紫红色）和内部的圆形。

有两种形状圆形和心形。我想添加椭圆形。

我添加了椭圆形，但没有用。

OverlayView.cs

public enum OverlayShape
    {
        Circle,
        Heart,
        Oval
    }

public static readonly BindableProperty ShapeProperty = BindableProperty.Create(
   propertyName: nameof(Shape),
   returnType: typeof(CameraOverlayShape),
   declaringType: typeof(CameraOverlayView),
   defaultValue: CameraOverlayShape.Oval,
   defaultBindingMode: BindingMode.TwoWay);

NativeOverlayView.cs

OverlayShape overlayShape = OverlayShape.Oval;

public OverlayShape Shape
{
    get { return overlayShape; }
    set
    {
        overlayShape = value;
        Redraw();

    }
}

Paint paint = new Paint(PaintFlags.AntiAlias)
{
    Color = OverlayBackgroundColor,
    Alpha = (int)(255 * Opacity)
};

RectF outerRectangle = new RectF(0, 0, width, height);

osCanvas.DrawRect(outerRectangle, paint);

switch (Shape)
{
    case OverlayShape.Oval:
        osCanvas.DrawOval(outerRectangle, paint);

        break;
    default:
    
    // Code
    
}

Answer 1

以下代码适用于我。

 case OverlayShape.Oval:
     shapeHeight = (float)(shapeHeight * 0.8);
     RectF rect = new RectF(width / 2- shapeWidth / 2, height / 2 - shapeHeight / 2, shapeWidth/2+ width/2 , shapeHeight/2+height/2);
     osCanvas.DrawOval(rect, paint);
     break;