CBManager状态始终未知

Question

我试图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”。关于为什么会这样的想法？

Answer 1

两件事情 -

1. 你的CBCentralManager应该是一个属性，否则它将在你退出时初始化它的方法被释放
2. 在处于通电状态之前，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];
   }

Answer 2

方法

- （无效）centralManagerDidUpdateState（CBCentralManager *）中央

叫做。试着实现这个

- (void)centralManagerDidUpdateState:(CBCentralManager *)central {
  // Possible states that the central manager can return.
  char *managerStrings[] = {"Unknown Error",            "Resetting",
                            "Unsupported Device",       "Unauthorized",
                            "Bluetooth is deactivated", "PoweredOn"};

  NSString *managerString =
      [NSString stringWithFormat:@"%s", managerStrings[central.state]];

  // the search is enabled if everything is ok
  if ([managerString isEqualToString:@"PoweredOn"]) {

      //Do something

  }
}

Answer 3

从Sierra，Xcode 8，Swift 3升级到High Sierra，Xcode 9，Swift 4后，我遇到了同样的问题。

• 解决方案1 ​​:(仅用于测试）在init和扫描开始之间等待第二位

  var scanner = BLESensorScanner(sensorName: sensorName);
  sleep(1);
  DispatchQueue.global(qos: .userInteractive).async {
      if (scanner.isPoweredOn()) {
          DBG("Bluetooth is powered on");
          scanner.startScan();
      }
      else {
          DBG("Bluetooth is not powered");
          exit(-1);
      }
  }

注意：BLESensorScanner实现NSObject，CBCentralManagerDelegate，CBPeripheralDelegate。 sensorName是蓝牙设备的名称

• 解决方案2：使用事件处理程序等待状态变为poweredOn

  public func centralManagerDidUpdateState(_ central: CBCentralManager) {
      DBG("CBCentralManager.centralManagerDidUpdateState");
      DBGI("state=\(toString(central.state))");
      if (state == CBManagerState.poweredOn) {
          scanner.startScan();
      }
  }