如何使用线程在迅速?
dispatchOnMainThread:^{
NSLog(@"Block Executed On %s", dispatch_queue_get_label(dispatch_get_current_queue()));
}];
如何使用线程在迅速?
dispatchOnMainThread:^{
NSLog(@"Block Executed On %s", dispatch_queue_get_label(dispatch_get_current_queue()));
}];
当前回答
下面的代码是否有缺点(当需要启动前台屏幕之后)?
import Foundation
import UIKit
class TestTimeDelay {
static var connected:Bool = false
static var counter:Int = 0
static func showAfterDelayControl(uiViewController:UIViewController) {
NSLog("TestTimeDelay", "showAfterDelayControl")
}
static func tryReconnect() -> Bool {
counter += 1
NSLog("TestTimeDelay", "Counter:\(counter)")
return counter > 4
}
static func waitOnConnectWithDelay(milliseconds:Int, uiViewController: UIViewController) {
DispatchQueue.global(qos: .background).async {
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + DispatchTimeInterval.milliseconds(milliseconds), execute: {
waitOnConnect(uiViewController: uiViewController)
})
}
}
static func waitOnConnect(uiViewController:UIViewController) {
connected = tryReconnect()
if connected {
showAfterDelayControl(uiViewController: uiViewController)
}
else {
waitOnConnectWithDelay(milliseconds: 200, uiViewController:uiViewController)
}
}
}
其他回答
斯威夫特5
为了简化,创建一个“DispatchQueue+Extensions.swift”文件,内容如下:
import Foundation
typealias Dispatch = DispatchQueue
extension Dispatch {
static func background(_ task: @escaping () -> ()) {
Dispatch.global(qos: .background).async {
task()
}
}
static func main(_ task: @escaping () -> ()) {
Dispatch.main.async {
task()
}
}
}
用法:
Dispatch.background {
// do stuff
Dispatch.main {
// update UI
}
}
好的答案,无论如何,我想分享我的面向对象的解决方案,直到swift 5。
请查看它:AsyncTask
从概念上受到android的AsyncTask的启发,我用Swift写了自己的类
AsyncTask允许正确和简单地使用UI线程。该类允许执行后台操作并在UI线程上发布结果。
下面是一些用法示例
例1 -
AsyncTask(backgroundTask: {(p:String)->Void in//set BGParam to String and BGResult to Void
print(p);//print the value in background thread
}).execute("Hello async");//execute with value 'Hello async'
例2 -
let task2=AsyncTask(beforeTask: {
print("pre execution");//print 'pre execution' before backgroundTask
},backgroundTask:{(p:Int)->String in//set BGParam to Int & BGResult to String
if p>0{//check if execution value is bigger than zero
return "positive"//pass String "poitive" to afterTask
}
return "negative";//otherwise pass String "negative"
}, afterTask: {(p:String) in
print(p);//print background task result
});
task2.execute(1);//execute with value 1
它有两个泛型类型:
BGParam -执行时发送给任务的参数类型。 BGResult -后台计算结果的类型。 当你创建一个AsyncTask时,你可以将这些类型传递给任何你需要传入和传入后台任务的类型,但如果你不需要这些类型,你可以将其标记为未使用的,只需将其设置为:Void或使用更短的语法:()
当一个异步任务执行时,它经过3个步骤:
beforeTask:()->在任务执行之前在UI线程上调用的Void。 backgroundTask: (param:BGParam)->BGResult在后台线程立即调用 afterTask:(参数:BGResult)->在UI线程上调用后台任务结果的Void
Dan Beaulieu在swift5中给出了答案(从swift 3.0.1开始也可以工作)。
斯威夫特5.0.1
extension DispatchQueue {
static func background(delay: Double = 0.0, background: (()->Void)? = nil, completion: (() -> Void)? = nil) {
DispatchQueue.global(qos: .background).async {
background?()
if let completion = completion {
DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
completion()
})
}
}
}
}
使用
DispatchQueue.background(delay: 3.0, background: {
// do something in background
}, completion: {
// when background job finishes, wait 3 seconds and do something in main thread
})
DispatchQueue.background(background: {
// do something in background
}, completion:{
// when background job finished, do something in main thread
})
DispatchQueue.background(delay: 3.0, completion:{
// do something in main thread after 3 seconds
})
快4.倍
把这些放到文件中:
func background(work: @escaping () -> ()) {
DispatchQueue.global(qos: .userInitiated).async {
work()
}
}
func main(work: @escaping () -> ()) {
DispatchQueue.main.async {
work()
}
}
然后在需要的地方调用它:
background {
//background job
main {
//update UI (or what you need to do in main thread)
}
}
你必须将你想要在后台运行的更改与你想要在UI上运行的更新分开:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
// do your task
dispatch_async(dispatch_get_main_queue()) {
// update some UI
}
}