我很乐意分享我的方法，因为所有其他方法都基于UIGestureRecognizerDelegate或子类化UIPanGestureRecognizer。
我的方法基于运行时和交换方法。我不确定这种方法是否完美，但你可以自己测试和改进它。
只需一行代码即可设置任何UIPanGestureRecognizer的方向：
UITableView().panGestureRecognizer.direction = UIPanGestureRecognizer.Direction.vertical
使用 pod 'UIPanGestureRecognizerDirection' 或以下代码：
public extension UIPanGestureRecognizer {
override open class func initialize() {
super.initialize()
guard self === UIPanGestureRecognizer.self else { return }
func replace(_ method: Selector, with anotherMethod: Selector, for clаss: AnyClass) {
let original = class_getInstanceMethod(clаss, method)
let swizzled = class_getInstanceMethod(clаss, anotherMethod)
switch class_addMethod(clаss, method, method_getImplementation(swizzled), method_getTypeEncoding(swizzled)) {
case true:
class_replaceMethod(clаss, anotherMethod, method_getImplementation(original), method_getTypeEncoding(original))
case false:
method_exchangeImplementations(original, swizzled)
}
}
let selector1 = #selector(UIPanGestureRecognizer.touchesBegan(_:with:))
let selector2 = #selector(UIPanGestureRecognizer.swizzling_touchesBegan(_:with:))
replace(selector1, with: selector2, for: self)
let selector3 = #selector(UIPanGestureRecognizer.touchesMoved(_:with:))
let selector4 = #selector(UIPanGestureRecognizer.swizzling_touchesMoved(_:with:))
replace(selector3, with: selector4, for: self)
}
@objc private func swizzling_touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
self.swizzling_touchesBegan(touches, with: event)
guard direction != nil else { return }
touchesBegan = true
}
@objc private func swizzling_touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
self.swizzling_touchesMoved(touches, with: event)
guard let direction = direction, touchesBegan == true else { return }
defer {
touchesBegan = false
}
let forbiddenDirectionsCount = touches
.flatMap({ ($0.location(in: $0.view) - $0.previousLocation(in: $0.view)).direction })
.filter({ $0 != direction })
.count
if forbiddenDirectionsCount > 0 {
state = .failed
}
}
}
public extension UIPanGestureRecognizer {
public enum Direction: Int {
case horizontal = 0
case vertical
}
private struct UIPanGestureRecognizerRuntimeKeys {
static var directions = "\(#file)+\(#line)"
static var touchesBegan = "\(#file)+\(#line)"
}
public var direction: UIPanGestureRecognizer.Direction? {
get {
let object = objc_getAssociatedObject(self, &UIPanGestureRecognizerRuntimeKeys.directions)
return object as? UIPanGestureRecognizer.Direction
}
set {
let policy = objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC
objc_setAssociatedObject(self, &UIPanGestureRecognizerRuntimeKeys.directions, newValue, policy)
}
}
fileprivate var touchesBegan: Bool {
get {
let object = objc_getAssociatedObject(self, &UIPanGestureRecognizerRuntimeKeys.touchesBegan)
return (object as? Bool) ?? false
}
set {
let policy = objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC
objc_setAssociatedObject(self, &UIPanGestureRecognizerRuntimeKeys.touchesBegan, newValue, policy)
}
}
}
fileprivate extension CGPoint {
var direction: UIPanGestureRecognizer.Direction? {
guard self != .zero else { return nil }
switch fabs(x) > fabs(y) {
case true: return .horizontal
case false: return .vertical
}
}
static func -(lhs: CGPoint, rhs: CGPoint) -> CGPoint {
return CGPoint(x: lhs.x - rhs.x, y: lhs.y - rhs.y)
}
}
