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()));
}];
来自Jameson Quave的教程
斯威夫特2
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
//All stuff here
})
Swift 3.0 +
在Swift 3.0中,很多东西都被现代化了。在后台队列上运行一些东西看起来像这样:
DispatchQueue.global(qos: .userInitiated).async {
print("This is run on a background queue")
DispatchQueue.main.async {
print("This is run on the main queue, after the previous code in outer block")
}
}
Swift 1.2到2.3
let qualityOfServiceClass = QOS_CLASS_USER_INITIATED
let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0)
dispatch_async(backgroundQueue, {
print("This is run on a background queue")
dispatch_async(dispatch_get_main_queue(), { () -> Void in
print("This is run on the main queue, after the previous code in outer block")
})
})
Pre Swift 1.2 -已知问题
从Swift 1.1开始,苹果在没有做一些修改的情况下不支持上述语法。传递qos_class_user_initialized实际上不起作用,而是使用Int(qos_class_user_initialized .value)。
有关更多信息,请参阅apple文档
最佳实践是定义一个可多次访问的可重用函数。
可重用的功能:
例如,AppDelegate.swift是一个全局函数。
func backgroundThread(_ delay: Double = 0.0, background: (() -> Void)? = nil, completion: (() -> Void)? = nil) {
dispatch_async(dispatch_get_global_queue(Int(QOS_CLASS_USER_INITIATED.value), 0)) {
background?()
let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
dispatch_after(popTime, dispatch_get_main_queue()) {
completion?()
}
}
}
注意:在Swift 2.0中替换QOS_CLASS_USER_INITIATED。使用QOS_CLASS_USER_INITIATED。rawValue相反
用法:
a .在后台运行一个进程,延迟3秒:
backgroundThread(3.0, background: {
// Your background function here
})
B.在后台运行一个进程,然后在前台运行一个补全:
backgroundThread(background: {
// Your function here to run in the background
},
completion: {
// A function to run in the foreground when the background thread is complete
})
C.延迟3秒-注意使用completion参数而不使用background参数:
backgroundThread(3.0, completion: {
// Your delayed function here to be run in the foreground
})
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
}
}
dispatch_async(dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0), {
// Conversion into base64 string
self.uploadImageString = uploadPhotoDataJPEG.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.EncodingEndLineWithCarriageReturn)
})
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
我真的很喜欢Dan Beaulieu的答案,但是它在Swift 2.2中不起作用,我认为我们可以避免那些讨厌的强制打开!
func backgroundThread(delay: Double = 0.0, background: (() -> Void)? = nil, completion: (() -> Void)? = nil) {
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) {
background?()
if let completion = completion{
let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
dispatch_after(popTime, dispatch_get_main_queue()) {
completion()
}
}
}
}
Swift 3版本
Swift 3利用新的DispatchQueue类来管理队列和线程。要在后台线程上运行一些东西,你可以使用:
let backgroundQueue = DispatchQueue(label: "com.app.queue", qos: .background)
backgroundQueue.async {
print("Run on background thread")
}
或者如果你想在两行代码中实现:
DispatchQueue.global(qos: .background).async {
print("Run on background thread")
DispatchQueue.main.async {
print("We finished that.")
// only back on the main thread, may you access UI:
label.text = "Done."
}
}
你也可以在本教程中获得一些关于Swift 3中GDC的深入信息。
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
})
由于OP问题已经在上面得到了回答,我只想添加一些速度方面的考虑:
我不建议使用.background线程优先级运行任务,尤其是在iPhone X上,因为任务似乎是分配在低功耗内核上的。
下面是一个计算密集型函数的一些真实数据,该函数从XML文件中读取(带缓冲)并执行数据插值:
设备名/ .background / .utility / .default / .userInitiated / .userInteractive
iPhone X: 18.7s / 6.3s / 1.8s / 1.8s iPhone 7: 4.6s / 3.1s / 3.0s / 2.8s / 2.6s iPhone 5s: 7.3s / 6.1s / 4.0s / 4.0s / 3.8s
注意,并不是所有设备的数据集都相同。iPhone X最大,iPhone 5s最小。
在我们的iOS应用中,中央调度是用来处理多任务的。
您可以使用此代码
// Using time interval
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now()+1) {
print("Hello World")
}
// Background thread
queue.sync {
for i in 0..<10 {
print("Hello", i)
}
}
// Main thread
for i in 20..<30 {
print("Hello", i)
}
更多信息请访问这个链接:https://www.programminghub.us/2018/07/integrate-dispatcher-in-swift.html
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)
}
}
在Swift 4.2中,这是可行的。
import Foundation
class myThread: Thread
{
override func main() {
while(true) {
print("Running in the Thread");
Thread.sleep(forTimeInterval: 4);
}
}
}
let t = myThread();
t.start();
while(true) {
print("Main Loop");
sleep(5);
}
多用途螺纹功能
public enum QueueType {
case Main
case Background
case LowPriority
case HighPriority
var queue: DispatchQueue {
switch self {
case .Main:
return DispatchQueue.main
case .Background:
return DispatchQueue(label: "com.app.queue",
qos: .background,
target: nil)
case .LowPriority:
return DispatchQueue.global(qos: .userInitiated)
case .HighPriority:
return DispatchQueue.global(qos: .userInitiated)
}
}
}
func performOn(_ queueType: QueueType, closure: @escaping () -> Void) {
queueType.queue.async(execute: closure)
}
像这样使用它:
performOn(.Background) {
//Code
}
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
}
}
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)
}
}
}