这是我在用户关闭应用程序时在后台执行的代码,但这是奇怪的行为,在执行 endBackgroundUpdateTask()
方法后,DispatchQueue
仍然没有停止...
我钢连续收到通知。
我做错了什么?
你可以尝试拿这段代码自己尝试一下,这真的很奇怪
var backgroundUpdateTask: UIBackgroundTaskIdentifier!
func beginBackgroundUpdateTask() {
print("beginBackgroundUpdateTask")
self.backgroundUpdateTask = UIApplication.shared.beginBackgroundTask(expirationHandler: {
self.endBackgroundUpdateTask()
})
}
func endBackgroundUpdateTask() {
print("endBackgroundUpdateTask")
UIApplication.shared.endBackgroundTask(self.backgroundUpdateTask)
self.backgroundUpdateTask = UIBackgroundTaskInvalid
}
func doBackgroundTask() {
print("Strart")
DispatchQueue.global().async {
self.beginBackgroundUpdateTask()
// Do something with the result.
let timer = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(AppDelegate.displayAlert), userInfo: nil, repeats: true)
RunLoop.current.add(timer, forMode: RunLoopMode.defaultRunLoopMode)
RunLoop.current.run()
// End the background task.
self.endBackgroundUpdateTask()
}
print("Finish")
}
func displayAlert() {
print("displayAlert")
let note = UILocalNotification()
note.alertBody = "As a test I'm hoping this will run in the background every X number of seconds..."
note.soundName = UILocalNotificationDefaultSoundName
UIApplication.shared.scheduleLocalNotification(note)
}
func applicationDidEnterBackground(_ application: UIApplication) {
log.debug("applicationDidEnterBackground")
self.doBackgroundTask()
}
编辑
var backgroundUpdateTask: UIBackgroundTaskIdentifier!
var timerr: Timer?
func beginBackgroundUpdateTask() {
appDeligate.log.debug("beginBackgroundUpdateTask")
self.backgroundUpdateTask = UIApplication.shared.beginBackgroundTask(expirationHandler: {
self.endBackgroundUpdateTask()
})
}
func endBackgroundUpdateTask() {
appDeligate.log.debug("endBackgroundUpdateTask")
UIApplication.shared.endBackgroundTask(self.backgroundUpdateTask)
self.backgroundUpdateTask = UIBackgroundTaskInvalid
timerr = nil
}
func doBackgroundTask() {
print("Strart")
DispatchQueue.global().async {
self.beginBackgroundUpdateTask()
// Do something with the result.
self.timerr = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(TestViewController.displayAlert), userInfo: nil, repeats: true)
RunLoop.current.add(self.timerr!, forMode: RunLoopMode.defaultRunLoopMode)
RunLoop.current.run()
// End the background task.
self.endBackgroundUpdateTask()
}
print("Finish")
}
func displayAlert() {
print("displayAlert")
let note = UILocalNotification()
note.alertBody = "As a test I'm hoping this will run in the background every X number of seconds..."
note.soundName = UILocalNotificationDefaultSoundName
UIApplication.shared.scheduleLocalNotification(note)
}
最佳答案
真正的问题是计时器,我需要放置这一行
timerr?.invalidate()
这里
func endBackgroundUpdateTask() {
appDeligate.log.debug("endBackgroundUpdateTask")
UIApplication.shared.endBackgroundTask(self.backgroundUpdateTask)
self.backgroundUpdateTask = UIBackgroundTaskInvalid
timerr?.invalidate()
}
但无论如何,这有点奇怪,因为我认为如果我停止 backgroundUpdate()
,里面的所有任务都必须自动失效和清除,但事实并非如此。
谢谢@matt
关于swift - 如何停止后台更新任务?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42050267/