ios - 带圆角的 UIView : how to clip subviews correctly?

Question

我创建了一个 UIView 的子类，它覆盖了 drawRect: 并使用 AddArcToPoint() 来绘制圆角。 (我不想使用图层的圆角半径属性，因为我需要定义哪些角必须圆角。)然而，我无法克服的问题是:如果我在 (0|0) 处添加一个 subview ，它会隐藏我的圆角。知道我该如何解决这个问题吗？我希望它能很好地剪裁。

下面是绘制圆角矩形的代码。它是 Monotouch，但任何开发人员都应该可以阅读。

(您可以在此处找到完整代码:https://github.com/Krumelur/RoundedRectView)

public override void Draw (RectangleF rect)
        {
            using (var oContext = UIGraphics.GetCurrentContext())
            {
                oContext.SetLineWidth (this.StrokeWidth);
                oContext.SetStrokeColor (this.oStrokeColor.CGColor);
                oContext.SetFillColor (this.oRectColor.CGColor);

                RectangleF oRect = this.Bounds;

                float fRadius = this.CornerRadius;
                float fWidth = oRect.Width;
                float fHeight = oRect.Height;

                // Make sure corner radius isn't larger than half the shorter side.
                if (fRadius > fWidth / 2.0f)
                {
                    fRadius = fWidth / 2.0f;
                }
                if (fRadius > fHeight / 2.0f)
                {
                    fRadius = fHeight / 2.0f;    
                }

                float fMinX = oRect.GetMinX ();
                float fMidX = oRect.GetMidX ();
                float fMaxX = oRect.GetMaxX ();
                float fMinY = oRect.GetMinY ();
                float fMidY = oRect.GetMidY ();
                float fMaxY = oRect.GetMaxY ();

                // Move to left middle.
                oContext.MoveTo (fMinX, fMidY);

                // Arc to top middle.
                oContext.AddArcToPoint (fMinX, fMinY, fMidX, fMinY, (this.RoundCorners & ROUND_CORNERS.TopLeft) == ROUND_CORNERS.TopLeft ? fRadius : 0);
                // Arc to right middle.
                oContext.AddArcToPoint (fMaxX, fMinY, fMaxX, fMidY, (this.RoundCorners & ROUND_CORNERS.TopRight) == ROUND_CORNERS.TopRight ? fRadius : 0);
                // Arc to bottom middle.
                oContext.AddArcToPoint (fMaxX, fMaxY, fMidX, fMaxY, (this.RoundCorners & ROUND_CORNERS.BottomRight) == ROUND_CORNERS.BottomRight ? fRadius : 0);
                // Arc to left middle.
                oContext.AddArcToPoint (fMinX, fMaxY, fMinX, fMidY, (this.RoundCorners & ROUND_CORNERS.BottomLeft) == ROUND_CORNERS.BottomLeft ? fRadius : 0);

                // Draw the path.
                oContext.ClosePath ();
                oContext.DrawPath (CGPathDrawingMode.FillStroke);
            }
        }

编辑:

这里有一段代码演示了如何使用 CALayer 解决它。

private void UpdateMask()
        {
            UIBezierPath oMaskPath = UIBezierPath.FromRoundedRect (this.Bounds, this.eRoundedCorners, new SizeF (this.fCornerRadius, this.fCornerRadius));

            CAShapeLayer oMaskLayer = new CAShapeLayer ();
            oMaskLayer.Frame = this.Bounds;
            oMaskLayer.Path = oMaskPath.CGPath;
            this.Layer.Mask = oMaskLayer;
        }

Answer 1

我还没有尝试过，但我认为你可以使用 CALayer 的 mask 属性来做到这一点。您必须将圆角矩形绘制到一个层中，该层被设置为 View 层的 mask 。