gpt4 book ai didi

Swift 以编程方式为带有闭包的按钮创建函数

转载 作者:搜寻专家 更新时间:2023-10-30 22:05:32 24 4
gpt4 key购买 nike

在 Swift 中,您可以像这样为按钮创建一个函数:

button.addTarget(self, action: #selector(buttonAction), forControlEvents: .TouchUpInside)

但是有没有办法我可以做这样的事情:

button.whenButtonIsClicked({Insert code here})

这样我什至不必为按钮声明一个显式函数。我知道我可以使用按钮标签,但我更愿意这样做。

最佳答案

创建您自己的 UIButton 子类来执行此操作:

class MyButton: UIButton {
var action: (() -> Void)?

func whenButtonIsClicked(action: @escaping () -> Void) {
self.action = action
self.addTarget(self, action: #selector(MyButton.clicked), for: .touchUpInside)
}

// Button Event Handler:
// I have not marked this as @IBAction because it is not intended to
// be hooked up to Interface Builder
@objc func clicked() {
action?()
}
}

当您以编程方式创建按钮时,将 MyButton 替换为 UIButton,然后调用 whenButtonIsClicked 来设置其功能。

您还可以将其与 Storyboard 中的 UIButton 一起使用(只需将其类更改为 MyButton),然后在 中调用 whenButtonIsClicked >viewDidLoad.

@IBOutlet weak var theButton: MyButton!

var count = 0

override func viewDidLoad() {
super.viewDidLoad()

// be sure to declare [unowned self] if you access
// properties or methods of the class so that you
// don't create a strong reference cycle
theButton.whenButtonIsClicked { [unowned self] in
self.count += 1
print("count = \(self.count)")
}

更强大的实现

认识到程序员可能想要处理比 .touchUpInside 更多的事件这一事实,我编写了这个功能更强大的版本,它支持每个 UIButton 多个闭包和每个事件多个闭包类型。

class ClosureButton: UIButton {
private var actions = [UInt : [((UIControl.Event) -> Void)]]()

private let funcDict: [UInt : Selector] = [
UIControl.Event.touchCancel.rawValue: #selector(eventTouchCancel),
UIControl.Event.touchDown.rawValue: #selector(eventTouchDown),
UIControl.Event.touchDownRepeat.rawValue: #selector(eventTouchDownRepeat),
UIControl.Event.touchUpInside.rawValue: #selector(eventTouchUpInside),
UIControl.Event.touchUpOutside.rawValue: #selector(eventTouchUpOutside),
UIControl.Event.touchDragEnter.rawValue: #selector(eventTouchDragEnter),
UIControl.Event.touchDragExit.rawValue: #selector(eventTouchDragExit),
UIControl.Event.touchDragInside.rawValue: #selector(eventTouchDragInside),
UIControl.Event.touchDragOutside.rawValue: #selector(eventTouchDragOutside)
]

func handle(events: [UIControl.Event], action: @escaping (UIControl.Event) -> Void) {
for event in events {
if var closures = actions[event.rawValue] {
closures.append(action)
actions[event.rawValue] = closures
} else {
guard let sel = funcDict[event.rawValue] else { continue }
self.addTarget(self, action: sel, for: event)
actions[event.rawValue] = [action]
}
}
}

private func callActions(for event: UIControl.Event) {
guard let actions = actions[event.rawValue] else { return }
for action in actions {
action(event)
}
}

@objc private func eventTouchCancel() { callActions(for: .touchCancel) }
@objc private func eventTouchDown() { callActions(for: .touchDown) }
@objc private func eventTouchDownRepeat() { callActions(for: .touchDownRepeat) }
@objc private func eventTouchUpInside() { callActions(for: .touchUpInside) }
@objc private func eventTouchUpOutside() { callActions(for: .touchUpOutside) }
@objc private func eventTouchDragEnter() { callActions(for: .touchDragEnter) }
@objc private func eventTouchDragExit() { callActions(for: .touchDragExit) }
@objc private func eventTouchDragInside() { callActions(for: .touchDragInside) }
@objc private func eventTouchDragOutside() { callActions(for: .touchDragOutside) }
}

演示

class ViewController: UIViewController {

var count = 0

override func viewDidLoad() {
super.viewDidLoad()

let button = ClosureButton(frame: CGRect(x: 50, y: 100, width: 60, height: 40))
button.setTitle("press me", for: .normal)
button.setTitleColor(.blue, for: .normal)

// Demonstration of handling a single UIControl.Event type.
// If your closure accesses self, be sure to declare [unowned self]
// to prevent a strong reference cycle
button.handle(events: [.touchUpInside]) { [unowned self] _ in
self.count += 1
print("count = \(self.count)")
}

// Define a second handler for touchUpInside:
button.handle(events: [.touchUpInside]) { _ in
print("I'll be called on touchUpInside too")
}

let manyEvents: [UIControl.Event] = [.touchCancel, .touchUpInside, .touchDown, .touchDownRepeat, .touchUpOutside, .touchDragEnter,
.touchDragExit, .touchDragInside, .touchDragOutside]

// Demonstration of handling multiple events
button.handle(events: manyEvents) { event in
switch event {
case .touchCancel:
print("touchCancel")
case .touchDown:
print("touchDown")
case .touchDownRepeat:
print("touchDownRepeat")
case .touchUpInside:
print("touchUpInside")
case .touchUpOutside:
print("touchUpOutside")
case .touchDragEnter:
print("touchDragEnter")
case .touchDragExit:
print("touchDragExit")
case .touchDragInside:
print("touchDragInside")
case .touchDragOutside:
print("touchDragOutside")
default:
break
}
}

self.view.addSubview(button)
}
}

关于Swift 以编程方式为带有闭包的按钮创建函数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/37903243/

24 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com