我已经在很长一段时间内一直在寻找这个问题的答案,所以我想我愿意冒一些downvotes来发布它。
基本上,我想让Apple提供的Apple Watch后台刷新示例代码实际工作(链接和代码如下)。
我已经在模拟器和带有Apple Watch Series 2的iPhone 6s上尝试过,后台任务从未成功完成到时间更新的地步。我已经尝试将手表应用程序固定到扩展坞上,并且我已经尝试将应用程序保留在前台并将其发送到后台,无论是在模拟器中还是在实际的手表上。我甚至尝试等待将近一年时间,看看Xcode或Apple Watch是否会收到更新,以使其正常工作。
是否有人成功修改了Apple提供的代码以使其正常工作?
您可以在此处下载整个可运行的示例项目:WatchBackgroundRefresh: Using WKRefreshBackgroundTask to update WatchKit apps in the background
/*
Copyright (C) 2016-2017 Apple Inc. All Rights Reserved.
See LICENSE.txt for this sample’s licensing information
Abstract:
The main interface controller.
*/
import WatchKit
import Foundation
class MainInterfaceController: WKInterfaceController, WKExtensionDelegate, URLSessionDownloadDelegate {
// MARK: Properties
let sampleDownloadURL = URL(string: "http://devstreaming.apple.com/videos/wwdc/2015/802mpzd3nzovlygpbg/802/802_designing_for_apple_watch.pdf?dl=1")!
@IBOutlet var timeDisplayLabel: WKInterfaceLabel!
private let dateFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .none
formatter.timeStyle = .long
return formatter
}()
// MARK: WKInterfaceController
override func awake(withContext context: Any?) {
super.awake(withContext: context)
// Configure interface objects here.
WKExtension.shared().delegate = self
updateDateLabel()
}
// MARK: WKExtensionDelegate
func handle(_ backgroundTasks: Set<WKRefreshBackgroundTask>) {
for task : WKRefreshBackgroundTask in backgroundTasks {
print("received background task: ", task)
// only handle these while running in the background
if (WKExtension.shared().applicationState == .background) {
if task is WKApplicationRefreshBackgroundTask {
// this task is completed below, our app will then suspend while the download session runs
print("application task received, start URL session")
scheduleURLSession()
}
}
else if let urlTask = task as? WKURLSessionRefreshBackgroundTask {
let backgroundConfigObject = URLSessionConfiguration.background(withIdentifier: urlTask.sessionIdentifier)
let backgroundSession = URLSession(configuration: backgroundConfigObject, delegate: self, delegateQueue: nil)
print("Rejoining session ", backgroundSession)
}
// make sure to complete all tasks, even ones you don't handle
task.setTaskCompleted()
}
}
// MARK: Snapshot and UI updating
func scheduleSnapshot() {
// fire now, we're ready
let fireDate = Date()
WKExtension.shared().scheduleSnapshotRefresh(withPreferredDate: fireDate, userInfo: nil) { error in
if (error == nil) {
print("successfully scheduled snapshot. All background work completed.")
}
}
}
func updateDateLabel() {
let currentDate = Date()
timeDisplayLabel.setText(dateFormatter.string(from: currentDate))
}
// MARK: URLSession handling
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
print("NSURLSession finished to url: ", location)
updateDateLabel()
scheduleSnapshot()
}
func scheduleURLSession() {
let backgroundConfigObject = URLSessionConfiguration.background(withIdentifier: NSUUID().uuidString)
backgroundConfigObject.sessionSendsLaunchEvents = true
let backgroundSession = URLSession(configuration: backgroundConfigObject)
let downloadTask = backgroundSession.downloadTask(with: sampleDownloadURL)
downloadTask.resume()
}
// MARK: IB actions
@IBAction func ScheduleRefreshButtonTapped() {
// fire in 20 seconds
let fireDate = Date(timeIntervalSinceNow: 20.0)
// optional, any SecureCoding compliant data can be passed here
let userInfo = ["reason" : "background update"] as NSDictionary
WKExtension.shared().scheduleBackgroundRefresh(withPreferredDate: fireDate, userInfo: userInfo) { (error) in
if (error == nil) {
print("successfully scheduled background task, use the crown to send the app to the background and wait for handle:BackgroundTasks to fire.")
}
}
}
}
在模拟器上运行时输出以下内容。在其他配置中运行时类似的输出(但不一定完全相同):
successfully scheduled background task, use the crown to send the app to the background and wait for handle:BackgroundTasks to fire.
received background task: <WKSnapshotRefreshBackgroundTask: 0x7b019030>
received background task: <WKApplicationRefreshBackgroundTask: 0x7a711290>
application task received, start URL session
答案 0 :(得分:6)
对于任何可能发现这一点的人来说,我看到了两个问题,都是使用URLSession调度。通过这些更改,我认为Apple示例代码实际上是可行的,至少在模拟器上是这样。
- sampleDownloadURL
需要安全,因此需要使用HTTPS的网址。这个有效:https://api.weather.gov/points/42.3584,-71.0598/forecast
- 我认为URLSession
的委托从未设置为self
,因此以下更改修复了该问题:
let backgroundSession = URLSession(configuration: backgroundConfigObject, delegate: self, delegateQueue: nil)
以下工作(虽然不太完整)代码非常有用:What's New in watchOS 3: Background Tasks
编辑:可能发生的另一个问题是任务在收到后立即完成。实际上,它们应该被保存(例如,在局部变量中),然后在完成该任务的所有处理之后完成。对于此代码,我认为这意味着挂在WKApplicationRefreshBackgroundTask
上,而不是在调用setTaskCompleted()
之后直接调用scheduleSnapshot
。