How to detect the bluetooth turn off in control center?

Bluetooth turn off from control center does not really close.
But I try to use "CoreBluetooth Framework" check the state.
When I turn off from the control center, the state still show "CBManagerStatePoweredOff".
Is it the bug? how can I distinguish between the turn off from control center and turn off from setting page.
I am use "CBCentralManagerDelegate":

• (void) centralManagerDidUpdateState:(CBCentralManager *)central{

switch (central.state) {
        case CBManagerStateUnknown:
            break;
        case CBManagerStateResetting:
            break;
        case CBManagerStateUnsupported:
            break;
        case CBManagerStateUnauthorized:
break;
        case CBManagerStatePoweredOff:
            break;
        case CBManagerStatePoweredOn:
            break;
        default:
            break;
    }
}