为什么我在iPad2上使用这个简单的代码时会得到CBCentralManagerStateUnknown？-(BOOL)viewDidLoad{bluetoothManager=[[CBCentralManageralloc]initWithDelegate:selfqueue:nil];if([managerstate]==CBCentralManagerStatePoweredOff)NSLog(@"CBCentralManagerStatePoweredOff");if([managerstate]==CBCentralManagerStatePoweredOn)NSLog(@"