我制作了Apple Watch Complication以查看回历日期，因此必须每天刷新一次，才能在ComplicationController.swift中做到这一点，我制作了时间表背景，如下所示：
WKExtension.shared().scheduleBackgroundRefresh(withPreferredDate: date, userInfo: nil) { _ in
}
然后在ExtensionDelegate.swift中，我像这样处理后台任务：
func handle(_ backgroundTasks: Set<WKRefreshBackgroundTask>) {
// Sent when the system needs to launch the application in the background to process tasks. Tasks arrive in a set, so loop through and process each one.
for task in backgroundTasks {
// Use a switch statement to check the task type
switch task {
case let backgroundTask as WKApplicationRefreshBackgroundTask:
// Be sure to complete the background task once you’re done.
ComplicationController().updateComplications()
backgroundTask.setTaskCompletedWithSnapshot(false)
case let snapshotTask as WKSnapshotRefreshBackgroundTask:
// Snapshot tasks have a unique completion call, make sure to set your expiration date
snapshotTask.setTaskCompleted(restoredDefaultState: true, estimatedSnapshotExpiration: Date.distantFuture, userInfo: nil)
case let connectivityTask as WKWatchConnectivityRefreshBackgroundTask:
// Be sure to complete the connectivity task once you’re done.
connectivityTask.setTaskCompletedWithSnapshot(false)
case let urlSessionTask as WKURLSessionRefreshBackgroundTask:
// Be sure to complete the URL session task once you’re done.
urlSessionTask.setTaskCompletedWithSnapshot(false)
case let relevantShortcutTask as WKRelevantShortcutRefreshBackgroundTask:
// Be sure to complete the relevant-shortcut task once you're done.
relevantShortcutTask.setTaskCompletedWithSnapshot(false)
case let intentDidRunTask as WKIntentDidRunRefreshBackgroundTask:
// Be sure to complete the intent-did-run task once you're done.
intentDidRunTask.setTaskCompletedWithSnapshot(false)
default:
// make sure to complete unhandled task types
task.setTaskCompletedWithSnapshot(false)
}
}
}
所有这些在模拟器中都可以正常工作，但在实际设备中却不行！ 发生另一件事-我不知道是否相关-：App运行后收到此消息：libMobileGestalt MGIOKitHelper.m：239：无法检索数据