iOS-BLE后台扫描会随机冻结

更新14/08-3-找到了真正的解决方案：

您可以在下面的答案中查看解决方案

更新16/06-2-可能是解决方案：

正如Sandy Chapman在其回答中的评论中所建议的，我现在可以使用以下方法在扫描开始时检索外围设备：

- (NSArray<CBPeripheral *> * nonnull)retrievePeripheralsWithIdentifiers:(NSArray<NSUUID *> * nonnull)identifiers

是检查返回数组的大小。每次出现错误时，它总是0。如果我的设备在当前运行之前没有进行任何连接，也可能会发生此错误。我还能够看到我的设备广告，并在另一台设备出现错误时，用另一台设备触发命令

2006年10月更新：

• 我让我的应用程序运行了一整晚，以检查是否有任何内存泄漏或大量资源使用，以下是我在后台运行12-14小时后的结果。内存/CPU使用率与我离开时完全相同。这让我觉得我的应用程序没有任何漏洞，可能导致iOS关闭它以恢复内存/CPU使用

更新08/06:

• 请注意，这不是一个广告问题，因为我们的BLE设备始终通电，并且我们使用了我们能找到的最强的BLE电子卡
• 这也不是iOS在后台检测时间的问题。我等了很长时间（20~30分钟）才确定不是这个问题

原始问题

我目前正在开发一款应用程序，可以处理与可移动设备的通信。我的一个限制是，只有在必须发送命令或读取数据时，我才必须连接到此设备。完成后，我必须尽快断开连接，以允许其他潜在用户也这样做

该应用程序的一个功能如下：

• 用户可以在应用程序处于后台时启用自动命令。如果在10分钟内未检测到设备，则会触发此自动命令
• 我的应用程序会一直扫描，直到找到我的设备
• 为了在需要时让它保持清醒，我每次都会重新启动扫描，因为CBCentralManagerScanOptionAllowDuplicatesKey选项不存在
• 当它被检测到时，我正在检查最后一次检测是否是在10分钟前。如果是这样，我连接到设备，然后写入与我需要的服务对应的特征

目标是在用户进入范围时触发此设备。它可能发生在超出范围的几分钟后，例如几小时，这取决于我的用户习惯

通过这种方式，一切都很正常，但有时（似乎是在随机时间发生的），扫描有点“冻结”。我的过程做得很好，但几次之后，我看到我的应用程序正在扫描，但我的DidDiscoveryPeripheral:从未调用回拨，即使我的测试设备就在我的设备前面。有时可能需要一段时间才能检测到，但在这里，几分钟后什么也没有发生

我原以为iOS可能会关闭我的应用程序以收回内存，但当我关闭和打开蓝牙时，CentralManagerDipDateState:才是正确的方法。如果我的应用程序在哪里被杀了，它不应该是这样的，对吗？ 如果我打开我的应用程序，扫描将重新启动，它将恢复正常。 我还检查了iOS是否在180秒后关闭了我的应用程序，但事实并非如此，因为在这段时间后，它工作正常

我已将.plist设置为具有正确的设置（UIBackgroundModes中的bluetooth central）。管理所有BLE处理的我的类存储在我的AppDelegate中，作为可通过我的所有应用访问的单例。我还测试了切换创建此对象的位置。目前我正在应用程序中创建它：didFinishLaunchingWithOptions:方法。我试图将其放入我的AppDelegate初始化：，但如果我在后台这样做，每次扫描都会失败

我不知道我可以向您展示代码的哪一部分来帮助您更好地理解我的流程。以下是一些可能会有所帮助的示例。请注意，“AT_appDelegate”是一个maccro，用于访问我的appDelegate

// Init of my DeviceManager class that handles all BLE processing
- (id) init {
   self = [super init];

   // Flags creation
   self.autoConnectTriggered = NO;
   self.isDeviceReady = NO;
   self.connectionUncomplete = NO;
   self.currentCommand = NONE;
   self.currentCommand_index = 0;

   self.signalOkDetectionCount = 0; // Helps to find out if device is at a good range or too far
   self.connectionFailedCount = 0;  // Helps in a "try again" process if a command fails

   self.main_uuid = [CBUUID UUIDWithString:MAINSERVICE_UUID];
   self.peripheralsRetainer = [[NSMutableArray alloc] init];
   self.lastDeviceDetection = nil;

   // Ble items creation
   dispatch_queue_t queue = dispatch_queue_create("com.onset.corebluetooth.queue", DISPATCH_QUEUE_SERIAL);
   self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:queue];

[self startScanning];
return self;
}

   // The way i start the scan
- (void) startScanning {

   if (!self.isScanning && self.centralManager.state == CBCentralManagerStatePoweredOn) {

    CLS_LOG(@"### Start scanning ###");
    self.isScanning = YES;

    NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:!self.isBackground] forKey:CBCentralManagerScanOptionAllowDuplicatesKey];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    [self.centralManager scanForPeripheralsWithServices:@[self.main_uuid] options:options];

    });
  }
  }

  // The way i stop and restart the scan after i've found our device. Contains    some of foreground (UI update) process that you can ignore
  - (void) stopScanningAndRestart: (BOOL) restart {

  CLS_LOG(@"### Scanning terminated ###");
  if (self.isScanning) {

    self.isScanning = NO;
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    [self.centralManager stopScan];
  });

  // Avoid clearing the connection when waiting for notification (remote + learning)

     if (!self.isWaitingNotifiy && !self.isSynchronizing && self.currentCommand == NONE ) {
        // If no device found during scan, update view

        if (self.deviceToReach == nil && !self.isBackground) {

            // Check if any connected devices last
            if (![self isDeviceStillConnected]) {
               CLS_LOG(@"--- Device unreachable for view ---");

            } else {

                self.isDeviceInRange = YES;
                self.deviceToReach = AT_appDelegate.user.device.blePeripheral;
            }

            [self.delegate performSelectorOnMainThread:@selector(updateView) withObject:nil waitUntilDone:YES];       

        }

        // Reset var
        self.deviceToReach = nil;
        self.isDeviceInRange = NO;
        self.signalOkDetectionCount = 0;

        // Check if autotrigger needs to be done again - If time interval is higher enough,
        // reset autoConnectTriggered to NO. If user has been away for <AUTOTRIGGER_INTERVAL>
        // from the device, it will trigger again next time it will be detected.

        if ([[NSDate date] timeIntervalSinceReferenceDate] - [self.lastDeviceDetection timeIntervalSinceReferenceDate] > AUTOTRIGGER_INTERVAL) {

            CLS_LOG(@"### Auto trigger is enabled ###");
            self.autoConnectTriggered = NO;
        }
    }
}


   if (restart) {
    [self startScanning];
   }
  }

  // Here is my detection process, the flag "isInBackground" is set up each    time the app goes background
  - (void) centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {

CLS_LOG(@"### : %@ -- %@", peripheral.name, RSSI);
BOOL deviceAlreadyShown = [AT_appDelegate isDeviceAvailable];

// If current device has no UUID set, check if peripheral is the right one
// with its name, containing his serial number (macaddress) returned by
// the server on remote adding

NSString *p1 = [[[peripheral.name stringByReplacingOccurrencesOfString:@":" withString:@""] stringByReplacingOccurrencesOfString:@"Extel " withString:@""] uppercaseString];

NSString *p2 = [AT_appDelegate.user.device.serial uppercaseString];

if ([p1 isEqualToString:p2]) {
    AT_appDelegate.user.device.scanUUID = peripheral.identifier;
}

// Filter peripheral connection with uuid
if ([AT_appDelegate.user.device.scanUUID isEqual:peripheral.identifier]) {
    if (([RSSI intValue] > REQUIRED_SIGNAL_STRENGTH && [RSSI intValue] < 0) || self.isBackground) {
        self.signalOkDetectionCount++;
        self.deviceToReach = peripheral;
        self.isDeviceInRange = (self.signalOkDetectionCount >= REQUIRED_SIGNAL_OK_DETECTIONS);

        [peripheral setDelegate:self];
        // Reset blePeripheral if daughter board has been switched and there were
        // not enough time for the software to notice connection has been lost.
        // If that was the case, the device.blePeripheral has not been reset to nil,
        // and might be different than the new peripheral (from the new daugtherboard)

       if (AT_appDelegate.user.device.blePeripheral != nil) {
            if (![AT_appDelegate.user.device.blePeripheral.name isEqualToString:peripheral.name]) {
                AT_appDelegate.user.device.blePeripheral = nil;
            }
        }

        if (self.lastDeviceDetection == nil ||
            ([[NSDate date] timeIntervalSinceReferenceDate] - [self.lastDeviceDetection timeIntervalSinceReferenceDate] > AUTOTRIGGER_INTERVAL)) {
            self.autoConnectTriggered = NO;
        }

        [peripheral readRSSI];
        AT_appDelegate.user.device.blePeripheral = peripheral;
        self.lastDeviceDetection = [NSDate date];

        if (AT_appDelegate.user.device.autoconnect) {
            if (!self.autoConnectTriggered && !self.autoTriggerConnectionLaunched) {
                CLS_LOG(@"--- Perform trigger ! ---");

                self.autoTriggerConnectionLaunched = YES;
                [self executeCommand:W_TRIGGER onDevice:AT_appDelegate.user.device]; // trigger !
                return;
            }
        }
    }

    if (deviceAlreadyShown) {
        [self.delegate performSelectorOnMainThread:@selector(updateView) withObject:nil waitUntilDone:YES];
    }
}

if (self.isBackground && AT_appDelegate.user.device.autoconnect) {
    CLS_LOG(@"### Relaunch scan ###");
    [self stopScanningAndRestart:YES];
}
  }

//我的DeviceManager类的Init，该类处理所有BLE处理
-（id）init{
self=[super init]；
//标志创建
self.autoConnectTriggered=否；
self.isdevicerady=否；
self.connectionUncomplete=否；
self.currentCommand=NONE；
self.currentCommand_index=0；
self.signalOkDetectionCount=0；//有助于确定设备是否处于良好范围内或距离过远
self.connectionFailedCount=0；//如果命令失败，将在“重试”过程中提供帮助
self.main_uuid=[CBUUID uuid withstring:MAINSERVICE_uuid]；
self.peripheralstainer=[[NSMutableArray alloc]init]；
self.lastDeviceDetection=nil；
//可编辑项目创建
dispatch\u queue\u t queue=dispatch\u queue\u create（“com.inition.corebooth.queue”，dispatch\u queue\u SERIAL）；
self.centralManager=[[CBCentralManager alloc]initWithDelegate:self-queue:queue]；
[自启动扫描]；
回归自我；
}
//我开始扫描的方式
-（无效）开始扫描{
如果（！self.isScanning&&self.centralManager.state==cbcentralmanager状态poweredon）{
CLS#U日志（@“####开始扫描###”）；
self.isScanning=是；
NSDictionary*options=[NSDictionary Dictionary WithObject:[NSNumber numberWithBool:！self.isBackground]forKey:CBCentralManager-CanOptionalLowDuplicateSkey]；
调度异步（调度获取全局队列（调度队列优先级默认为0）^{
[self.centralManager扫描外设服务：@[self.main_uuid]选项：选项]；
});
}
}
//找到设备后停止并重新启动扫描的方式。包含一些可以忽略的前台（UI更新）进程
-（无效）停止扫描和启动：（布尔）
// Init of my DeviceManager class that handles all BLE processing
- (id) init {
   self = [super init];

   // Flags creation
   self.autoConnectTriggered = NO;
   self.isDeviceReady = NO;
   self.connectionUncomplete = NO;
   self.currentCommand = NONE;
   self.currentCommand_index = 0;

   self.signalOkDetectionCount = 0; // Helps to find out if device is at a good range or too far
   self.connectionFailedCount = 0;  // Helps in a "try again" process if a command fails

   self.main_uuid = [CBUUID UUIDWithString:MAINSERVICE_UUID];
   self.peripheralsRetainer = [[NSMutableArray alloc] init];
   self.lastDeviceDetection = nil;

   // Ble items creation
   dispatch_queue_t queue = dispatch_queue_create("com.onset.corebluetooth.queue", DISPATCH_QUEUE_SERIAL);
   self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:queue];

[self startScanning];
return self;
}

   // The way i start the scan
- (void) startScanning {

   if (!self.isScanning && self.centralManager.state == CBCentralManagerStatePoweredOn) {

    CLS_LOG(@"### Start scanning ###");
    self.isScanning = YES;

    NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:!self.isBackground] forKey:CBCentralManagerScanOptionAllowDuplicatesKey];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    [self.centralManager scanForPeripheralsWithServices:@[self.main_uuid] options:options];

    });
  }
  }

  // The way i stop and restart the scan after i've found our device. Contains    some of foreground (UI update) process that you can ignore
  - (void) stopScanningAndRestart: (BOOL) restart {

  CLS_LOG(@"### Scanning terminated ###");
  if (self.isScanning) {

    self.isScanning = NO;
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    [self.centralManager stopScan];
  });

  // Avoid clearing the connection when waiting for notification (remote + learning)

     if (!self.isWaitingNotifiy && !self.isSynchronizing && self.currentCommand == NONE ) {
        // If no device found during scan, update view

        if (self.deviceToReach == nil && !self.isBackground) {

            // Check if any connected devices last
            if (![self isDeviceStillConnected]) {
               CLS_LOG(@"--- Device unreachable for view ---");

            } else {

                self.isDeviceInRange = YES;
                self.deviceToReach = AT_appDelegate.user.device.blePeripheral;
            }

            [self.delegate performSelectorOnMainThread:@selector(updateView) withObject:nil waitUntilDone:YES];       

        }

        // Reset var
        self.deviceToReach = nil;
        self.isDeviceInRange = NO;
        self.signalOkDetectionCount = 0;

        // Check if autotrigger needs to be done again - If time interval is higher enough,
        // reset autoConnectTriggered to NO. If user has been away for <AUTOTRIGGER_INTERVAL>
        // from the device, it will trigger again next time it will be detected.

        if ([[NSDate date] timeIntervalSinceReferenceDate] - [self.lastDeviceDetection timeIntervalSinceReferenceDate] > AUTOTRIGGER_INTERVAL) {

            CLS_LOG(@"### Auto trigger is enabled ###");
            self.autoConnectTriggered = NO;
        }
    }
}


   if (restart) {
    [self startScanning];
   }
  }

  // Here is my detection process, the flag "isInBackground" is set up each    time the app goes background
  - (void) centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {

CLS_LOG(@"### : %@ -- %@", peripheral.name, RSSI);
BOOL deviceAlreadyShown = [AT_appDelegate isDeviceAvailable];

// If current device has no UUID set, check if peripheral is the right one
// with its name, containing his serial number (macaddress) returned by
// the server on remote adding

NSString *p1 = [[[peripheral.name stringByReplacingOccurrencesOfString:@":" withString:@""] stringByReplacingOccurrencesOfString:@"Extel " withString:@""] uppercaseString];

NSString *p2 = [AT_appDelegate.user.device.serial uppercaseString];

if ([p1 isEqualToString:p2]) {
    AT_appDelegate.user.device.scanUUID = peripheral.identifier;
}

// Filter peripheral connection with uuid
if ([AT_appDelegate.user.device.scanUUID isEqual:peripheral.identifier]) {
    if (([RSSI intValue] > REQUIRED_SIGNAL_STRENGTH && [RSSI intValue] < 0) || self.isBackground) {
        self.signalOkDetectionCount++;
        self.deviceToReach = peripheral;
        self.isDeviceInRange = (self.signalOkDetectionCount >= REQUIRED_SIGNAL_OK_DETECTIONS);

        [peripheral setDelegate:self];
        // Reset blePeripheral if daughter board has been switched and there were
        // not enough time for the software to notice connection has been lost.
        // If that was the case, the device.blePeripheral has not been reset to nil,
        // and might be different than the new peripheral (from the new daugtherboard)

       if (AT_appDelegate.user.device.blePeripheral != nil) {
            if (![AT_appDelegate.user.device.blePeripheral.name isEqualToString:peripheral.name]) {
                AT_appDelegate.user.device.blePeripheral = nil;
            }
        }

        if (self.lastDeviceDetection == nil ||
            ([[NSDate date] timeIntervalSinceReferenceDate] - [self.lastDeviceDetection timeIntervalSinceReferenceDate] > AUTOTRIGGER_INTERVAL)) {
            self.autoConnectTriggered = NO;
        }

        [peripheral readRSSI];
        AT_appDelegate.user.device.blePeripheral = peripheral;
        self.lastDeviceDetection = [NSDate date];

        if (AT_appDelegate.user.device.autoconnect) {
            if (!self.autoConnectTriggered && !self.autoTriggerConnectionLaunched) {
                CLS_LOG(@"--- Perform trigger ! ---");

                self.autoTriggerConnectionLaunched = YES;
                [self executeCommand:W_TRIGGER onDevice:AT_appDelegate.user.device]; // trigger !
                return;
            }
        }
    }

    if (deviceAlreadyShown) {
        [self.delegate performSelectorOnMainThread:@selector(updateView) withObject:nil waitUntilDone:YES];
    }
}

if (self.isBackground && AT_appDelegate.user.device.autoconnect) {
    CLS_LOG(@"### Relaunch scan ###");
    [self stopScanningAndRestart:YES];
}
  }

// Initialisation
dispatch_queue_t queue = dispatch_queue_create("com.onset.corebluetooth.queue", DISPATCH_QUEUE_SERIAL);
self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:queue options:@{CBCentralManagerOptionRestoreIdentifierKey:RESTORE_KEY}];

// Start scanning
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   [self.centralManager scanForPeripheralsWithServices:@[self.main_uuid] options:options];
});

// Stop scanning
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   [self.centralManager stopScan];
});

// Initialisation
self.bluetoothQueue = dispatch_queue_create("com.onset.corebluetooth.queue", DISPATCH_QUEUE_SERIAL);
    self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:self.bluetoothQueue options:@{CBCentralManagerOptionRestoreIdentifierKey:RESTORE_KEY}];

// Start scanning
dispatch_async(self.bluetoothQueue, ^{
   [self.centralManager scanForPeripheralsWithServices:@[self.main_uuid] options:options];
});

// Stop scanning
dispatch_async(self.bluetoothQueue, ^{
   [self.centralManager stopScan];
});

@property (atomic, strong) dispatch_queue_t bluetoothQueue;