ios - 如何在平移手势事件期间转换一条线？

Question

我正在创建一个流程图，当用户拖动一个节点时，我想移动连接到它的线。在节点的 pan 处理程序事件中，我实现了 CGAffineTransform转换线，但它不会平滑移动线。知道其他流程图应用程序如何处理这个问题吗？

func panHandler(sender: UIPanGestureRecognizer) {

        else if (sender.state == .Changed)
        {
            let translation = sender.translationInView(self)
            sender.view!.center = CGPointMake(originalCenter.x + translation.x, originalCenter.y + translation.y)


           //rv is the connected line, created at an other place like:
           //let w = GraphViewController.calcLength(e.x, y0: e.y, x1: e2.x, y1: e2.y)
           //rv = UIView(frame: CGRectMake(0, 0, CGFloat(w), 1.0))
           //var angle = GraphViewController.calcAngle(e.x, y0: e.y, x1: e2.x, y1: e2.y)
           //rv.transform = CGAffineTransformMakeRotation(CGFloat(angle))

            var angle = GraphViewController.calcAngle(e!.x, y0: e!.y, x1: r.destination!.x, y1:r.destination!.y)
            rv!.transform = CGAffineTransformMakeRotation(CGFloat(angle))

        }
    }

Answer 1

因为您不需要在线上的任何触摸事件，我们可以使用简单的 CAShapeLayer并更新其在 pan 上的路径。我假设你想为这条线设置一些 anchor 。

为您的线定义一些 anchor

endOfLineAnchor = CGPoint(x: view.bounds.width / 2, y: view.bounds.height * 0.8)

创建一些 View 以将其附加到

ballView = createBallView()
ballView.center = CGPoint(x: view.bounds.width / 2, y: view.bounds.height / 2)

添加图层和 View

    lineLayer = CAShapeLayer()
    lineLayer.strokeColor = UIColor.blackColor().CGColor
    lineLayer.path = pathFromBallToAnchor()
    view.layer.addSublayer(lineLayer)
    view.addSubview(ballView)

在平移更新图层的路径

    else if (sender.state == .Changed)
    {
        let translation = sender.translationInView(self.view)
        sender.view!.center = CGPointMake(originalCenter.x + translation.x, originalCenter.y + translation.y)
        CATransaction.begin()
        CATransaction.setValue(kCFBooleanTrue, forKey: kCATransactionDisableActions)
        lineLayer.path = pathFromBallToAnchor()
        CATransaction.commit()
    }

CATransaction 的原因是我们要禁用隐式动画。

构建路径:

    func pathFromBallToAnchor() -> CGPathRef {
        var bazier = UIBezierPath()
        bazier.moveToPoint(ballView.center)
        bazier.addLineToPoint(endOfLineAnchor)
        return bazier.CGPath
    }

结果: