ios监听电话事件

self.callCenter = [[CTCallCenter alloc] init];
self.callCenter.callEventHandler=^(CTCall* call)
{
    if (call.callState == CTCallStateDisconnected)
    {
        NSLog(@"挂断电话Call has been disconnected");     
    }
    else if (call.callState == CTCallStateConnected)
    {
         NSLog(@"电话通了Call has just been connected");  
    }
    else if(call.callState == CTCallStateIncoming)
    {
        NSLog(@"来电话了Call is incoming");  
    }
    else if (call.callState ==CTCallStateDialing)
    {
        NSLog(@"正在播电话call is dialing");  
    }
    else
    {
        NSLog(@"Nothing is done");  
    }
};