wcsession - watchOS 后台任务在 setTaskCompleted 上崩溃
问题描述
在我的手表扩展委托init
函数中,我在以下位置设置了 KVO 观察者WCSession
:
if WCSession.isSupported() {
let defaultSession = WCSession.default
defaultSession.addObserver(self, forKeyPath: "activationState",
options: [.old, .new],
context: &ExtensionDelegate.wcSessionKVOcontext)
defaultSession.addObserver(self, forKeyPath: "hasContentPending",
options: [.old, .new],
context: &ExtensionDelegate.wcSessionKVOcontext)
}
为了完成所有的watch后台任务,这里调用了函数
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if context == &ExtensionDelegate.wcSessionKVOcontext {
printStatusChanges(keyPath: keyPath, change: change)
DispatchQueue.main.async {
self.completeAllTasksIfReady()
}
}
}
和
private func completeAllTasksIfReady() {
let session = WCSession.default
// the session's properties only have valid values if the session is activated, so check that first
if session.activationState == .activated && !session.hasContentPending {
if wcBackgroundTasks.isEmpty {
print("No background tasks")
} else {
wcBackgroundTasks.forEach { $0.setTaskCompleted() }
print("\(wcBackgroundTasks.count) connectivity background tasks completed")
}
wcBackgroundTasks.removeAll()
}
}
通常,这可以正常工作。
但是,我在以下日志中崩溃了:
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x1db2eda8 __abort_with_payload + 24
1 libsystem_kernel.dylib 0x1db2ae60 abort_with_payload_wrapper_internal + 60
2 libsystem_kernel.dylib 0x1db2ae24 abort_with_payload_wrapper_internal + 0
3 WatchKit 0x2ddfce86 -[WKRefreshBackgroundTask setTaskCompleted] + 414
4 Watch Extension 0x00037258 closure #1 in ExtensionDelegate.completeAllTasksIfReady() + 209496 (ExtensionDelegate.swift:196)
5 Watch Extension 0x000372b0 thunk for @callee_guaranteed (@owned WKRefreshBackgroundTask) -> (@error @owned Error) + 209584 (ExtensionDelegate.swift:0)
6 Watch Extension 0x0003af08 partial apply for thunk for @callee_guaranteed (@owned WKRefreshBackgroundTask) -> (@error @owned Error) + 225032 (ExtensionDelegate.swift:0)
7 libswiftCore.dylib 0x00525350 0x2fc000 + 2265936
8 libswiftCore.dylib 0x00433b7c 0x2fc000 + 1276796
9 libswiftCore.dylib 0x00304060 0x2fc000 + 32864
10 Watch Extension 0x00036eec ExtensionDelegate.completeAllTasksIfReady() + 208620 (ExtensionDelegate.swift:196)
11 Watch Extension 0x000350d4 closure #1 in ExtensionDelegate.observeValue(forKeyPath:of:change:context:) + 200916 (ExtensionDelegate.swift:108)
12 Watch Extension 0x0000993c _T0Ieg_IeyB_TR + 22844 (AlertManager.swift:0)
13 libdispatch.dylib 0x1d9d3456 _dispatch_call_block_and_release + 10
14 libdispatch.dylib 0x1d9d3432 _dispatch_client_callout + 6
15 libdispatch.dylib 0x1d9e3604 _dispatch_main_queue_callback_4CF$VARIANT$mp + 858
16 CoreFoundation 0x1df7db1e __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 10
17 CoreFoundation 0x1df7b73c __CFRunLoopRun + 932
18 CoreFoundation 0x1dec7660 CFRunLoopRunSpecific + 534
19 GraphicsServices 0x1fb7ab3e GSEventRunModal + 94
20 UIKit 0x24746604 UIApplicationMain + 156
21 libxpc.dylib 0x1dcf7b14 _xpc_objc_main + 586
22 libxpc.dylib 0x1dcf94a8 xpc_main + 154
23 Foundation 0x1e9b2cf2 service_connection_handler + 0
24 PlugInKit 0x2525c06e -[PKService run] + 676
25 WatchKit 0x2de1b036 main + 162
26 libdyld.dylib 0x1da2e782 start + 2
显然,在其中一项任务 setTaskCompleted
中调用时会发生崩溃。WKRefreshBackgroundTask
但是可能是什么原因,或者如何调试呢?
解决方案
我的错。Apple 回复了我的错误报告:
此问题的行为基于以下内容:
- 这是一个断言,以确保同一任务不会多次完成
- 这由“WKWatchConnectivityRefreshBackgroundTask: 0x16e7b230
已完成的调用”指示<br> - 这很可能指向项目代码中的一个(或多个)错误,而不是 SDK/API
因此,我仔细检查了我的代码中是否有可能多次调用WKWatchConnectivityRefreshBackgroundTask
函数。setTaskCompleted
确实是这样:
当我开始开发我的手表扩展时,我复制了Apple 演示代码。它包含以下功能:
func handle(_ backgroundTasks: Set<WKRefreshBackgroundTask>) {
for backgroundTask in backgroundTasks {
if let wcBackgroundTask = backgroundTask as? WKWatchConnectivityRefreshBackgroundTask {
// store a reference to the task objects as we might have to wait to complete them
self.wcBackgroundTasks.append(wcBackgroundTask)
} else {
// immediately complete all other task types as we have not added support for them
backgroundTask.setTaskCompleted()
}
}
completeAllTasksIfReady()
}
在这里,WKWatchConnectivityRefreshBackgroundTask
应该处理的 a 存储在一个数组wcBackgroundTasks
中。稍后在completeAllTasksIfReady()
这个数组中的所有任务都由wcBackgroundTasks.forEach { $0.setTaskCompleted() }
.
我的错是我将 my 存储WKWatchConnectivityRefreshBackgroundTask
在这个数组中(稍后调用setTaskCompleted
它)并立即处理它并设置setTaskCompleted
. 所以这被调用了两次。
感谢发现这个的苹果工程师。
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