ios - CBManager 状态始终未知

Question

我正在尝试检查设备的蓝牙是打开还是关闭。这是我到目前为止编写的代码

   CBCentralManager *cbManager = [[CBCentralManager alloc] initWithDelegate:self
                                                                       queue:nil
                                                                     options:
                                   [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:0]
                                                               forKey:CBCentralManagerOptionShowPowerAlertKey]];


    [cbManager scanForPeripheralsWithServices:nil options:
                                    [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:0]
                                                                forKey:CBCentralManagerOptionShowPowerAlertKey]];

    if (cbManager.state==CBCentralManagerStatePoweredOff)
    {
        //do stuff
    }

- (void)centralManagerDidUpdateState:(CBCentralManager *)central
{
    NSString *stateString = nil;
    switch(bluetoothManager.state)
    {
        case CBCentralManagerStateResetting: stateString = @"The connection with the system service was momentarily lost, update imminent."; break;
        case CBCentralManagerStateUnsupported: stateString = @"The platform doesn't support Bluetooth Low Energy."; break;
        case CBCentralManagerStateUnauthorized: stateString = @"The app is not authorized to use Bluetooth Low Energy."; break;
        case CBCentralManagerStatePoweredOff: stateString = @"Bluetooth is currently powered off."; break;
        case CBCentralManagerStatePoweredOn: stateString = @"Bluetooth is currently powered on and available to use."; break;
        default: stateString = @"State unknown, update imminent."; break;
    }
    UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Bluetooth state"
                                                     message:stateString
                                                    delegate:nil
                                           cancelButtonTitle:@"Okay" otherButtonTitleArray:nil] autorelease];
    [alert show];
}

问题是无论设备上的蓝牙是否打开，管理器的状态始终为未知。关于为什么会发生这种情况的任何想法？

Answer 1

两件事-

1. 您的CBCentralManager 应该是一个属性，否则它会在您初始化它的方法退出时立即释放

2. 在您处于开机状态之前，您不应该调用 scanForPeripheralsWithServices。

   @property (strong,nonatomic) CBCentralManager *cbManager;
   
   
   
   self.cbManager = [[CBCentralManager alloc] initWithDelegate:self
                                                                  queue:nil
                                                                options:
                              [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:0]
                                                                  forKey:CBCentralManagerOptionShowPowerAlertKey]];
   
   
   - (void)centralManagerDidUpdateState:(CBCentralManager *)central
    {
       NSString *stateString = nil;
       switch(central.state)
       {
           case CBCentralManagerStateResetting: 
              stateString = @"The connection with the system service was momentarily lost, update imminent."; 
              break;
           case CBCentralManagerStateUnsupported: 
              stateString = @"The platform doesn't support Bluetooth Low Energy."; 
              break;
           case CBCentralManagerStateUnauthorized: 
              stateString = @"The app is not authorized to use Bluetooth Low Energy."; 
              break;
           case CBCentralManagerStatePoweredOff: 
              stateString = @"Bluetooth is currently powered off."; 
              break;
           case CBCentralManagerStatePoweredOn: 
              stateString = @"Bluetooth is currently powered on and available to use.";
              [central scanForPeripheralsWithServices:nil options:
                               [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:0]
                                                           forKey:CBCentralManagerOptionShowPowerAlertKey]]; 
              break;
           default: 
              stateString = @"State unknown, update imminent."; 
              break;
       }
       UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Bluetooth state"
                                                        message:stateString
                                                       delegate:nil
                                              cancelButtonTitle:@"Okay" otherButtonTitleArray:nil] autorelease];
       [alert show];
   }