ios - 拖动 UIView

Question

我需要一些帮助来拖动 UIView 以显示主视图下方的菜单 View 。

我有两个 UIView。menuView - 包括菜单按钮和标签 和 mainView - 位于 menuView 之上。

我想从左边缘拖动主视图以显示菜单项并将主视图对齐到特定位置。我可以向右拖动，但向左拖动时无法将其设置回原始位置。

这是我一直在尝试但没有成功的代码。我还想在将 mainView 向右拖动时使其变小。任何帮助将不胜感激。

注意:PanGesture 附加到 mainView。

@IBAction func dragMenu(_ sender: UIPanGestureRecognizer) {
    let mview = sender.view!
    let originalCenter = CGPoint(x: self.mainView.bounds.width/2, y: self.mainView.bounds.height/2)
    switch sender.state {

    case .changed:
        if let mview = sender.view {
            mview.center.x = mview.center.x + sender.translation(in: view).x
            sender.setTranslation(CGPoint.zero, in: view)
        }

    case .ended:


            let DraggedHalfWayRight = mview.center.x > view.center.x
            if DraggedHalfWayRight {
                //dragginToRight

                showMenu = !showMenu
                self.mainViewRight.constant = 200
                                    self.mainTop.constant = 50
                                    self.mainBottom.constant = 50
                                    self.mainLeft.constant = 200

            } else //dragging left and set it back to original position.
            {
                mview.center = originalCenter
                 showMenu = !showMenu
        }



    default:
        break
    }
}

Answer 1

我会提出一些建议:

1. 拖完菜单后，确保将其 alpha 设置为零(这样，如果您在纵向模式下转到横向模式，您不会突然看那里的菜单)。

2. 我个人只是调整拖动 View 的 transform 并避免一直将手势的平移重置为零。这是个人喜好问题。

3. 我会让 View Controller 成为手势的委托(delegate)并实现 gestureRecognizerShouldBegin(因为如果菜单被隐藏，您不想识别滑动以尝试再次隐藏它; 如果它没有隐藏，你不想识别滑动来显示它)。

4. 在确定是否完成手势时，我还会考虑手势的速度(例如，轻弹一下就会关闭/显示动画 View )。

因此:

class ViewController: UIViewController {

    @IBOutlet weak var menuView: UIView!

    var isMenuVisible = true

    @IBAction func dragMenu(_ gesture: UIPanGestureRecognizer) {
        let translationX = gesture.translation(in: gesture.view!).x

        switch gesture.state {
        case .began:
            // if the menu is not visible, make sure it's off screen and then make it visible

            if !isMenuVisible {
                menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width, y: 0)
                menuView.alpha = 1
            }
            fallthrough

        case .changed:
            if isMenuVisible {
                menuView.transform = CGAffineTransform(translationX: translationX, y: 0)
            } else {
                menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width + translationX, y: 0)
            }

        case .ended:
            let shouldComplete: Bool
            if isMenuVisible {
                shouldComplete = translationX > gesture.view!.bounds.width / 2 || gesture.velocity(in: gesture.view!).x > 0
            } else {
                shouldComplete = -translationX > gesture.view!.bounds.width / 2 || gesture.velocity(in: gesture.view!).x < 0
            }

            UIView.animate(withDuration: 0.25, animations: {
                if self.isMenuVisible && shouldComplete || !self.isMenuVisible && !shouldComplete {
                    self.menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width, y: 0)
                } else {
                    self.menuView.transform = .identity
                }

                if shouldComplete{
                    self.isMenuVisible = !self.isMenuVisible
                }
            }, completion: { _ in
                self.menuView.alpha = self.isMenuVisible ? 1 : 0
            })

        default:
            break
        }
    }

}

extension ViewController: UIGestureRecognizerDelegate {

    func gestureRecognizerShouldBegin(_ gesture: UIGestureRecognizer) -> Bool {
        guard let gesture = gesture as? UIPanGestureRecognizer else { return true }

        let translationX = gesture.translation(in: gesture.view!).x

        return isMenuVisible && translationX > 0 || !isMenuVisible && translationX < 0
    }

}

---

就个人而言，我更喜欢使用单独的屏幕边缘手势识别器将菜单拉回到屏幕上(你真的不希望它识别任何地方的手势，但只是在右边缘)。这种方法的另一个优点是通过在不同的函数中保留“显示”和“隐藏”，代码可读性更高(恕我直言):

class ViewController: UIViewController {

    @IBOutlet weak var menuView: UIView!

    var isMenuVisible = true

    @IBAction func handleScreenEdgeGesture(_ gesture: UIScreenEdgePanGestureRecognizer) {
        let translationX = gesture.translation(in: gesture.view!).x

        switch gesture.state {
        case .began:
            menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width, y: 0)
            menuView.alpha = 1
            fallthrough

        case .changed:
            menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width + translationX, y: 0)

        case .ended:
            let shouldComplete = -translationX > gesture.view!.bounds.width / 2 || gesture.velocity(in: gesture.view!).x < 0

            UIView.animate(withDuration: 0.25, delay:0, options: .curveEaseOut, animations: {
                if shouldComplete {
                    self.menuView.transform = .identity
                    self.isMenuVisible = !self.isMenuVisible
                } else {
                    self.menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width, y: 0)
                }
            }, completion: { _ in
                self.menuView.alpha = self.isMenuVisible ? 1 : 0
            })

        default:
            break
        }
    }

    @IBAction func dragMenu(_ gesture: UIPanGestureRecognizer) {
        let translationX = gesture.translation(in: gesture.view!).x

        switch gesture.state {
        case .began, .changed:
            menuView.transform = CGAffineTransform(translationX: translationX, y: 0)

        case .ended:
            let shouldComplete = translationX > gesture.view!.bounds.width / 2 || gesture.velocity(in: gesture.view!).x > 0

            UIView.animate(withDuration: 0.25, delay:0, options: .curveEaseOut, animations: {
                if shouldComplete {
                    self.menuView.transform = CGAffineTransform(translationX: gesture.view!.bounds.width, y: 0)
                    self.isMenuVisible = !self.isMenuVisible
                } else {
                    self.menuView.transform = .identity
                }
            }, completion: { _ in
                self.menuView.alpha = self.isMenuVisible ? 1 : 0
            })

        default:
            break
        }
    }

}

extension ViewController: UIGestureRecognizerDelegate {

    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        if gestureRecognizer is UIScreenEdgePanGestureRecognizer {
            return !isMenuVisible
        } else if let gesture = gestureRecognizer as? UIPanGestureRecognizer {
            let translationX = gesture.translation(in: gesture.view!).x
            return isMenuVisible && translationX > 0
        }

        return true
    }

}