如何在用户接听电话后保留本机手机用户界面,例如whatsapp吗？

此外,如何在开始拨出电话时显示本机电话用户界面？

这是我的providerDelegate代码：

func reportIncomingCall(uuid: UUID,handle: String,hasVideo: Bool = false,completion: ((NSError?) -> Void)? = nil) {
    // Construct a CXCallUpdate describing the incoming call,including     the caller.
    let update = CXCallUpdate()
    update.remoteHandle = CXHandle(type: .generic,value: handle)
    update.hasVideo = hasVideo

    // Report the incoming call to the system
    provider.reportNewIncomingCall(with: uuid,update: update) { error in
        /*
         Only add incoming call to the app's list of calls if the call was allowed (i.e. there was no error)
         since calls may be "denied" for varIoUs legitimate reasons. See CXErrorCodeIncomingCallError.
         */
        if error == nil {
            print("calling")

        }
    }
}

func provider(_ provider: CXProvider,perform action: CXStartCallAction) {
    let update = CXCallUpdate()
    update.remoteHandle = action.handle

    provider.reportOutgoingCall(with: action.uuid,startedConnectingAt: Date())
    NotificationCenter.default.post(name: NSNotification.Name(rawValue: "callStart"),object: self,userInfo: ["uuid":action.uuid])
    action.fulfill(withDateStarted: Date())

}

func provider(_ provider: CXProvider,perform action: CXAnswerCallAction) {
    NotificationCenter.default.post(name: NSNotification.Name(rawValue: "callStart"),userInfo: ["uuid":action.uuid])

    // ACCEPT CALL ON SIP MANAGER
    if let voiceCallManager = AppDelegate.voiceCallManager {
        voiceCallManager.acceptCall()
    }

    action.fulfill(withDateConnected: Date())

}