objective-c - 是什么导致 iOS 中的 CBCentralManager State Unknown？

Question

为什么我在 iPad 2 上使用这个简单的代码时会得到 CBCentralManagerStateUnknown？

- (BOOL)viewDidLoad {

    bluetoothManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];

    if ([manager state] == CBCentralManagerStatePoweredOff) NSLog(@"CBCentralManagerStatePoweredOff");
    if ([manager state] == CBCentralManagerStatePoweredOn) NSLog(@"CBCentralManagerStatePoweredOn");
    if ([manager state] == CBCentralManagerStateResetting) NSLog(@"CBCentralManagerStateResetting");
    if ([manager state] == CBCentralManagerStateUnauthorized) NSLog(@"CBCentralManagerStateUnauthorized");
    if ([manager state] == CBCentralManagerStateUnknown) NSLog(@"CBCentralManagerStateUnknown");
    if ([manager state] == CBCentralManagerStateUnsupported) NSLog(@"CBCentralManagerStateUnsupported");

}

我不明白 CBCentralManagerStateUnknown 是什么意思。我该怎么办？ Apple docs就说:

State unknown, update imminent.

我在连接蓝牙设备时收到此响应，在蓝牙关闭时也收到此响应。如果我尝试运行类似 [manager retrieveConnectedPeripherals] 的程序，我还会在控制台中收到此消息:

CoreBluetooth[WARNING] <CBConcreteCentralManager: ...> is not powered on

Answer 1

我知道为什么从不调用委托(delegate)。因为对象从内存中删除了。就做一个强大的属性

@property (strong, nonatomic) DiscoverBluetoothDevices *btDevices;

在初始化

@implementation DiscoverBluetoothDevices
- (id) init
{
    self = [super init];
    if(self) {
        centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:dispatch_get_main_queue()];
        [centralManager scanForPeripheralsWithServices:nil options:@{CBCentralManagerScanOptionAllowDuplicatesKey: @YES}];

    }
    return self;
}

现在委托(delegate)被正确调用了。