C# Xamarin iOS UIBezierPath将方向更改为底部

我想在图像上画一条路径，它表示Xamarin中的半进度条。然后它适用于顶部

但现在我想画底部。但是我试了又试，没有找到任何东西

这张图片会解释你。

守则：

public CircleGraph(UIImageView imageView, int lineWidth, float percentComplete) : base(imageView.Frame)
{
    Initialise(imageView, lineWidth, percentComplete);
}

void Initialise(UIImageView imageView, int lineWidth, float percentComplete)
{
    _lineWidth = lineWidth;
    _percentComplete = percentComplete;
    this.BackgroundColor = UIColor.Clear;

    this.backgroundImage = imageView;
    Add(backgroundImage);

    centerPoint = new CGPoint(Bounds.GetMidX(), Bounds.Height);
    maskLayer = new CAShapeLayer();
    maskLayer.FillColor = UIColor.Blue.CGColor;
    maskLayer.StrokeColor = UIColor.Black.ColorWithAlpha(.5f).CGColor;
    maskLayer.LineWidth = _lineWidth;
    maskLayer.LineCap = CAShapeLayer.CapButt;

    this.Layer.Mask = maskLayer;
}

public void SetClipping(float percentComplete) {
    _percentComplete = percentComplete;
    SetNeedsDisplay();
}

public override void Draw(CoreGraphics.CGRect rect)
{
    base.Draw(rect);

    using (CGContext g = UIGraphics.GetCurrentContext())
    {
        _radius = (int)(this.Bounds.Width / 2) - _lineWidth / 2;

        // Top
        var startAngle = -(float)Math.PI;
        var endAngle = startAngle + HALF_CIRCLE * _percentComplete;

        maskPath = new UIBezierPath();
        maskPath.AddArc(centerPoint, _radius, startAngle, endAngle, false);
        maskLayer.Path = maskPath.CGPath;
    };
}

非常感谢

我找到了

只需将你的高度中心点设置为0，然后使用startAngle、endAngle和顺时针进行游戏，就可以了