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87 lines
3.1 KiB
Swift
87 lines
3.1 KiB
Swift
/*
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Copyright (C) 2015 Apple Inc. All Rights Reserved.
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See LICENSE.txt for this sample’s licensing information
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Abstract:
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Contains the code related to automatic background tasks
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*/
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import UIKit
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/**
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`BackgroundObserver` is an `EarthquakeOperationObserver` that will
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automatically begin and end a background task if the application transitions to the
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background. This would be useful if you had a vital `EarthquakeOperation`
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whose execution *must* complete, regardless of the activation state of the app.
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Some kinds network connections may fall in to this category, for example.
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*/
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class BackgroundObserver: NSObject, EarthquakeOperationObserver {
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// MARK: Properties
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private var identifier = UIBackgroundTaskIdentifier.invalid
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private var isInBackground = false
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override init() {
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super.init()
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// We need to know when the application moves to/from the background.
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NotificationCenter.default.addObserver(self, selector: #selector(BackgroundObserver.didEnterBackground(notification:)), name: UIApplication.didEnterBackgroundNotification, object: nil)
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NotificationCenter.default.addObserver(self, selector: #selector(BackgroundObserver.didEnterForeground(notification:)), name: UIApplication.didBecomeActiveNotification, object: nil)
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isInBackground = UIApplication.shared.applicationState == .background
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// If we're in the background already, immediately begin the background task.
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if isInBackground {
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startBackgroundTask()
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}
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}
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deinit {
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NotificationCenter.default.removeObserver(self)
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}
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@objc func didEnterBackground(notification: NSNotification) {
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if !isInBackground {
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isInBackground = true
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startBackgroundTask()
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}
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}
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@objc func didEnterForeground(notification: NSNotification) {
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if isInBackground {
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isInBackground = false
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endBackgroundTask()
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}
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}
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private func startBackgroundTask() {
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if identifier == UIBackgroundTaskIdentifier.invalid {
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identifier = UIApplication.shared.beginBackgroundTask(withName: "BackgroundObserver", expirationHandler: {
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self.endBackgroundTask()
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})
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}
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}
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private func endBackgroundTask() {
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if identifier != UIBackgroundTaskIdentifier.invalid {
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UIApplication.shared.endBackgroundTask(convertToUIBackgroundTaskIdentifier(identifier.rawValue))
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identifier = UIBackgroundTaskIdentifier.invalid
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}
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}
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// MARK: Operation Observer
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func operationDidStart(operation: EarthquakeOperation) { }
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func operation(operation: EarthquakeOperation, didProduceOperation newOperation: Operation) { }
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func operationDidFinish(operation: EarthquakeOperation, errors: [NSError]) {
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endBackgroundTask()
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}
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}
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// Helper function inserted by Swift 4.2 migrator.
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fileprivate func convertToUIBackgroundTaskIdentifier(_ input: Int) -> UIBackgroundTaskIdentifier {
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return UIBackgroundTaskIdentifier(rawValue: input)
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}
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