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iosswiftvoipcallkit

CallKit CXCallController.request error com.apple.CallKit.error.requesttransaction Code=6 while app is in the background

This error only occurs in iOS 13.3.1. It does not occur on iOS 13.3.0 or earlier.

If the app is in the foreground and it calls CXCallController.request, it works fine. But once I background the app and execute 'CXCallController.request' (triggered by the headphone play button), I get the following error: 

Error requesting transaction: Error Domain=com.apple.CallKit.error.requesttransaction Code=6 "(null)"

Code 6 is CXErrorCodeRequestTransactionError.Code.invalidAction

Here's a snippet of the sample code

let uuid = UUID()
let handle = CXHandle(type: .emailAddress, value: "[email protected]")

let startCallAction = CXStartCallAction(call: uuid, handle: handle)

let transaction = CXTransaction(action: startCallAction)
callController.request(transaction) { error in
    if let error = error {
        print("Error requesting transaction: \(error)")
    } else {
        print("Requested transaction successfully")
    }
}

The same code works fine in iOS 13.3.0 and earlier regardless if the app is foreground or background. Maybe this is a 13.3.1 bug or maybe Apple implemented some security measure while apps is in the background? But I don't see it in the iOS 13.3.1 release notes.

Solution

  • I found a work around to my own question. It may only work to my specific condition. It may not solve the problem for all error code=6. Just so you know.

    The way to fix this is that you have to be playing audio before you call CXCallController.request(:) when your app is in the background. You can even play a silent sound for a second if you want. It doesn't have to be an audible sound.

    If it doesn't work, you can try using dispatch async with a 0.1 second delay to call CXCallController.request(:). The idea is that you need to make sure the audio engine is active when you call CXCallController.request(:).