我正在编写一个iOS应用程序，在用户添加新数据(条形码扫描仪、扫描码)后，该应用程序需要在后台定期发送更新。我找不到任何方法可以在后台通过SMTP和mailcore2发送邮件，而不会出现问题和限制。
我已经试过了：
-
尝试使用后台提取https://developer.apple.com/documentation/uikit/core_app/managing_your_app_s_life_cycle/preparing_your_app_to_run_in_the_background/updating_your_app_with_background_app_refresh但这是非常不规则的，需要一段时间才能触发。
-
在AppDelegate.swift中：
func applicationDidEnterBackground(_ application: UIApplication) {
BackgroundTask.run(application: application) { [...] }
}
但是，只有当我关闭/最小化应用程序时，才会发送数据，如果BackgroundTask没有完成，应用程序将冻结，我收到这个错误：XPC连接中断我也遇到了问题，因为我需要等待sendOperation返回，但由于这是异步的，我构建了一个变通方法来保持线程运行，并在之后处理我的"如果成功，其他…"。完整代码中的更多信息：
typealias CompletionHandler = (Error?) -> Void
/// Provides syncronous access to results returned by
/// asynchronous processes with completion handlers
class SyncMaker {
var result: Error? = nil
/// Generates a synchronous-compliant completion handler
func completion() -> CompletionHandler{
return {
(error: Error?) in
// Store result, return control
self.result = error
CFRunLoopStop(CFRunLoopGetCurrent())
}
}
// Perform task (that must use custom completion handler) and wait
func run(_ task: @escaping () -> Void) -> Error? {
task()
CFRunLoopRun()
return result
}
}
func applicationDidEnterBackground(_ application: UIApplication) {
BackgroundTask.run(application: application) { backgroundTask in
if (scanManager.hasDataToSend()) {
let smtpSession = MCOSMTPSession()
let settings: Settings = scanManager.getSettings()
smtpSession.hostname = settings.credMailServer
smtpSession.username = settings.credMailSource
print(settings.credMailSource)
smtpSession.password = settings.credMailPassword
smtpSession.port = UInt32(settings.credMailPort)
[…] Setting auth and connection typ
smtpSession.isCheckCertificateEnabled = false
smtpSession.timeout = 100
smtpSession.connectionLogger = {(connectionID, type, data) in
if data != nil {
if let string = NSString(data: data!, encoding: String.Encoding.utf8.rawValue){
NSLog("Connectionlogger: (string)")
}
}
}
let builder = MCOMessageBuilder()
builder.header.to = [MCOAddress(displayName: settings.credMailDest, mailbox: settings.credMailDest)!]
builder.header.from = MCOAddress(displayName: settings.credMailSource, mailbox: settings.credMailSource)
builder.header.subject = "ScanLMS"
builder.htmlBody = ""
guard let attachment = MCOAttachment(data: scanManager.getSendData().data(using: .ascii), filename: "scans.txt") else {
print("Cant init attachment!")
backgroundTask.end()
return
}
attachment.mimeType = "text/plain"
builder.addAttachment(attachment)
let rfc822Data = builder.data()
let sendOperation = smtpSession.sendOperation(with: rfc822Data!)
var sendingError: Bool = true
print("Trying to send mail...")
if (sendOperation != nil) {
print("Starting sendOperation...")
let syncMaker = SyncMaker() //full class on top of code
let result = syncMaker.run {
sendOperation?.start(
syncMaker.completion())
}
if (result != nil) {
print("Error sending email: (result!)")
} else {
sendingError = false
print("Successfully sent email!")
}
} else {
print("Cant init sendOperation")
sendingError = true
}
if (sendingError) {
print("Error, returning")
} else {
print("Send done")
print("Updating scanManager with send data...")
scanManager.updateSendData()
print("Done, returning")
}
} else {
print("No new send data")
}
backgroundTask.end()
}
}
我将smtpSession.timeout=100降低到3(秒)，现在它不再阻塞UI。与其说是破解，不如说是解决方案，但它确实有效。