iPhone call duration

For our iPhone application, we would like to call a particular phone number, then fetch the total duration of that call after it has 开发者_运维知识库completed. This is to manage the billing of that particular phone call.

How can we determine the duration of a call executed in this manner?

Well you can do this with CoreTelephony but this will only give you some guess work. You can't exactly time the call on the iPhone.

If I kill the app when calling the number there is no way for you to get the total time spend on the call. And CoreTelephony can only tell you that a call is started not wether your app started the call. Also you app will be suspended (Become inactive) when the call starts. Also when the call is finished the user will have to start your app again since the user isn't automatically returned to your app.

After the call when the user presses the home button you apps gets background, thus you really can't keep track of the call.