Question

此功能适用于iOS 11上的设备，但我的设备已更新至iOS 12，它不再起作用：

//the viewcontroller is initiated with UIGestureRecognizerDelegate

let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(longPress))

//in cellForRowAt:
longPressGesture.minimumPressDuration = 1.0
longPressGesture.delegate = self
longPressGesture.cancelsTouchesInView = false
cell.addGestureRecognizer(longPressGesture)

@objc func longPress(longPressGestureRecognizer: UILongPressGestureRecognizer) {
     //never called
}

我还尝试将手势识别器添加到viewDidLoad中的按钮，以确保它与tableview无关，并且longPress函数仍未调用。

Answer 1

//the viewcontroller is initiated with UIGestureRecognizerDelegate
let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(longPress))

似乎您正在尝试将longPressGesture设置为UIViewController的实例属性，同时为其提供目标和操作作为其初始化程序的一部分。那是行不通的，因为在初始化时，目标self不是实例。还没有实例；实例就是我们正在创建的过程！

相反，将该行移到cellForRowAt:中，如下所示：

//in cellForRowAt:
let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(longPress))
longPressGesture.minimumPressDuration = 1.0
longPressGesture.delegate = self
longPressGesture.cancelsTouchesInView = false
cell.addGestureRecognizer(longPressGesture)

UILongPressGestureRecognizer未调用其目标方法

1 个答案: