ios 关于通话状态监听

    _callCenter = [[CTCallCenter alloc] init];//定义为成员变量

    _callCenter.callEventHandler=^(CTCall* call){        if([call.callState isEqualToString:CTCallStateDisconnected])        {            NSLog(@"呼叫已断开连接");               }else if([call.callState isEqualToString:CTCallStateIncoming]){            NSLog(@"呼叫进来");                    }else if([call.callState isEqualToString:CTCallStateConnected]) {            NSLog(@"电话已连接");        }else if([call.callState isEqualToString:CTCallStateDialing]) {            NSLog(@"呼叫状态拨号");        }else{            NSLog(@"没有任何事情完成");        }    };