永远不会调用CTCallCenter callEventHandler

Question

我尝试使用CTCallCenter接收来自iPhone的来电。当应用程序处于活动状态时，我会调用设备，并且不会调用callEventHandler。

可能是什么原因？

我在iPhone 5和XCode7上安装了IOS9.0 beta3。

我的代码：

- (void)viewDidLoad {
[super viewDidLoad];

CTCallCenter *callCenter = [[CTCallCenter alloc] init];
callCenter.callEventHandler = ^(CTCall* call)
{
    if (call.callState == CTCallStateDisconnected)
    {
        NSLog(@"Call has been disconnected");
        [self ShowMessage:@"Call has been disconnected"];
    }
    else if (call.callState == CTCallStateConnected)
    {
        NSLog(@"Call has just been connected");
        [self ShowMessage:@"Call has just been connected"];
    }
    else if(call.callState == CTCallStateIncoming)
    {
        NSLog(@"Call is incoming");
        [self ShowMessage:@"Call is incoming"];
    }
    else
    {
        NSLog(@"None of the conditions");
        [self ShowMessage:@"None of the conditions"];
    }
  };
}