是否有一种方法可以在延迟后用一个基本参数调用块,就像使用performSelector:withObject:afterDelay:但是使用int/double/float这样的参数?
当前回答
您可以使用dispatch_after稍后调用一个块。在Xcode中,开始输入dispatch_after并按Enter键自动完成如下内容:
下面是一个使用两个浮点数作为“参数”的示例。你不需要依赖任何类型的宏,代码的意图是非常清楚的:
斯威夫特3,斯威夫特4
let time1 = 8.23
let time2 = 3.42
// Delay 2 seconds
DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
print("Sum of times: \(time1 + time2)")
}
斯威夫特2
let time1 = 8.23
let time2 = 3.42
// Delay 2 seconds
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(2.0 * Double(NSEC_PER_SEC))), dispatch_get_main_queue()) { () -> Void in
println("Sum of times: \(time1 + time2)")
}
Objective - C
CGFloat time1 = 3.49;
CGFloat time2 = 8.13;
// Delay 2 seconds
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
CGFloat newTime = time1 + time2;
NSLog(@"New time: %f", newTime);
});
其他回答
PerformSelector:WithObject总是接受一个对象,因此为了传递诸如int/double/float等参数.....你可以用这样的东西。
//NSNumber是一个对象
[self performSelector:@selector(setUserAlphaNumber:)
withObject: [NSNumber numberWithFloat: 1.0f]
afterDelay:1.5];
-(void) setUserAlphaNumber: (NSNumber*) number{
[txtUsername setAlpha: [number floatValue] ];
}
同样的方式,你可以使用[NSNumber numberWithInt:]等....在接收方法中,您可以将数字转换为[数字int]或[数字double]的格式。
这里有一个方便的帮手来防止烦人的GCD调用一遍又一遍:
public func delay(bySeconds seconds: Double, dispatchLevel: DispatchLevel = .main, closure: @escaping () -> Void) {
let dispatchTime = DispatchTime.now() + seconds
dispatchLevel.dispatchQueue.asyncAfter(deadline: dispatchTime, execute: closure)
}
public enum DispatchLevel {
case main, userInteractive, userInitiated, utility, background
var dispatchQueue: DispatchQueue {
switch self {
case .main: return DispatchQueue.main
case .userInteractive: return DispatchQueue.global(qos: .userInteractive)
case .userInitiated: return DispatchQueue.global(qos: .userInitiated)
case .utility: return DispatchQueue.global(qos: .utility)
case .background: return DispatchQueue.global(qos: .background)
}
}
}
现在你只需在主线程上延迟你的代码,就像这样:
delay(bySeconds: 1.5) {
// delayed code
}
如果你想延迟你的代码到不同的线程:
delay(bySeconds: 1.5, dispatchLevel: .background) {
// delayed code that will run on background thread
}
如果你喜欢一个框架,也有一些更方便的功能,然后签出handysswift。你可以通过Carthage将它添加到你的项目中,然后像上面的例子一样使用它:
import HandySwift
delay(bySeconds: 1.5) {
// delayed code
}
如何使用Xcode内置代码片段库?
Swift更新:
许多向上的投票激励我更新这个答案。
内置的Xcode代码片段库只针对objective-c语言有dispatch_after。人们也可以为Swift创建自己的自定义代码片段。
用Xcode写。
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(<#delayInSeconds#> * Double(NSEC_PER_SEC))), dispatch_get_main_queue(), {
<#code to be executed after a specified delay#>
})
拖动此代码并将其放入代码片段库区域。
在代码段列表的底部,将有一个名为My code snippet的新实体。编辑这个标题。在输入Xcode时,请填写完成快捷方式。
有关更多信息,请参阅creatingcustomcodesnippet。
更新Swift 3
拖动此代码并将其放入代码片段库区域。
DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(<#delayInSeconds#>)) {
<#code to be executed after a specified delay#>
}
以下是在Swift中延迟后触发阻塞的方法:
runThisAfterDelay(seconds: 2) { () -> () in
print("Prints this 2 seconds later in main queue")
}
/// EZSwiftExtensions
func runThisAfterDelay(seconds seconds: Double, after: () -> ()) {
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(seconds * Double(NSEC_PER_SEC)))
dispatch_after(time, dispatch_get_main_queue(), after)
}
它包括作为一个标准函数在我的回购。
Swift 3和Xcode 8.3.2
这段代码将帮助你,我也添加了一个解释
// Create custom class, this will make your life easier
class CustomDelay {
static let cd = CustomDelay()
// This is your custom delay function
func runAfterDelay(_ delay:Double, closure:@escaping ()->()) {
let when = DispatchTime.now() + delay
DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
}
}
// here how to use it (Example 1)
class YourViewController: UIViewController {
// example delay time 2 second
let delayTime = 2.0
override func viewDidLoad() {
super.viewDidLoad()
CustomDelay.cd.runAfterDelay(delayTime) {
// This func will run after 2 second
// Update your UI here, u don't need to worry to bring this to the main thread because your CustomDelay already make this to main thread automatically :)
self.runFunc()
}
}
// example function 1
func runFunc() {
// do your method 1 here
}
}
// here how to use it (Example 2)
class YourSecondViewController: UIViewController {
// let say you want to user run function shoot after 3 second they tap a button
// Create a button (This is programatically, you can create with storyboard too)
let shootButton: UIButton = {
let button = UIButton(type: .system)
button.frame = CGRect(x: 15, y: 15, width: 40, height: 40) // Customize where do you want to put your button inside your ui
button.setTitle("Shoot", for: .normal)
button.translatesAutoresizingMaskIntoConstraints = false
return button
}()
override func viewDidLoad() {
super.viewDidLoad()
// create an action selector when user tap shoot button
shootButton.addTarget(self, action: #selector(shoot), for: .touchUpInside)
}
// example shoot function
func shoot() {
// example delay time 3 second then shoot
let delayTime = 3.0
// delay a shoot after 3 second
CustomDelay.cd.runAfterDelay(delayTime) {
// your shoot method here
// Update your UI here, u don't need to worry to bring this to the main thread because your CustomDelay already make this to main thread automatically :)
}
}
}
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