Canvas DBSignatureView中的双线

Question

我正在使用Objective c在我的应用程序中实现数字签名，但是当我点击屏幕并拖动手指时，该行被切成两半。

这是代码：

UIScrollView *contenido = [[UIScrollView alloc] init];
contenido.bounces = NO;

DBSignatureView *vistaFirma = [[DBSignatureView alloc] initWithFrame:CGRectMake(0, y, (margen-5) , tamCelda=tamCanvas)];
    [
  [![enter image description here][1]][1]vistaFirma addGestureRecognizer:gestureRecognizer];
    vistaFirma.userInteractionEnabled = NO;
    vistaFirma.layer.borderColor = [UIColor colorWithWhite:1.0f alpha:1.0f].CGColor;
    vistaFirma.layer.borderWidth = 1.0f;

    [contenido insertSubview:vistaFirma atIndex:contenido.subviews.count-(contenido.subviews.count > 1 ? 1 : 0)];

我应该实施哪个属性？