向MKPolyline

Question

我试图将方向箭头添加到MKPolyline，我几乎得到了它，但由于某种原因，一些箭头被切断（见下面的屏幕截图）。我在使用Core Graphics进行绘图方面表现不佳，所以我的猜测就是它的内容。任何人都有关于如何处理剪切箭头的任何指示？

以下代码使用子类化MKPolylineRenderer的drawMapRect:zoomScale:inContext:方法绘制图形：

  MKMapPoint prevMapPoint = mapPoints[0];
  MKMapPoint mapPoint = mapPoints[1];
  for (NSUInteger i = 1; i < pointCount; i++) {
    mapPoint = _mapPoints[i];
    CGPoint prevCGPt = [self pointForMapPoint:prevMapPoint];
    CGPoint cgPoint = [self pointForMapPoint:mapPoint];
    CGFloat bearing = atan2(cgPoint.y - prevCGPt.y, cgPoint.x - prevCGPt.x) - M_PI;

    //Get other two corners of triangle
    CGFloat arrowAngle = degreesToRadians(40.0);
    CGPoint pt2 = PointAtBearingFromPoint(cgPoint, bearing+arrowAngle/2, arrowLength);
    CGPoint pt3 = PointAtBearingFromPoint(cgPoint, bearing-arrowAngle/2, arrowLength);

    //Draw triangle and fill
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, cgPoint.x, cgPoint.y); //go to tip of triangle
    CGContextAddLineToPoint(context, pt2.x, pt2.y);
    CGContextAddLineToPoint(context, pt3.x, pt3.y);
    CGContextClosePath(context);
    CGContextFillPath(context);
  }

  prevMapPoint = mapPoint;

（同样在drawMapRect:zoomScale:inContext:方法中是一个For循环来决定放置每个箭头的位置并填充mapPoints数组，但我假设这不是问题）。