说明:
我使用核心蓝牙框架连接到BTLE外设，将外设标识符保存在数据库中，同时将外设保存在阵列中以处理与外设的重新连接。但是，当用户手动退出应用程序时，我的阵列变成空的。因此，我将无法再次重新连接这些外围设备。
现在，我的数据库中有外设标识符。我已阅读有关内容，发现有一个委托方法
- (NSArray<CBPeripheral *> *)retrievePeripheralsWithIdentifiers:(NSArray<NSUUID *> *)identifiers NS_AVAILABLE(NA, 7_0)
要获得外围设备，但它什么也没有返回。如何重新获得外围设备？
https://developer.apple.com/library/content/documentation//NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/BestPracticesForInteractingWithARemotePeripheralDevice/BestPracticesForInteractingWithA
我也检查了上述文件。他们提到了重新连接外围设备的方法
Retrieving a List of Known Peripherals
The first time you discover a peripheral, the system generates an identifier (a UUID, represented by an NSUUID object) to identify the peripheral. You can then store this identifier (using, for instance, the resources of the NSUserDefaults class), and later use it to try to reconnect to the peripheral using the retrievePeripheralsWithIdentifiers: method of the CBCentralManager class. The following describes one way to use this method to reconnect to a peripheral you’ve previously connected to.
When your app launches, call the retrievePeripheralsWithIdentifiers: method, passing in an array containing the identifiers of the peripherals you’ve previously discovered and connected to (and whose identifiers you have saved), like this:
knownPeripherals =
[myCentralManager retrievePeripheralsWithIdentifiers:savedIdentifiers];
The central manager tries to match the identifiers you provided to the identifiers of previously discovered peripherals and returns the results as an array of CBPeripheral objects. If no matches are found, the array is empty and you should try one of the other two reconnection options. If the array is not empty, let the user select (in the UI) which peripheral to try to reconnect to.
When the user selects a peripheral, try to connect to it by calling the connectPeripheral:options: method of the CBCentralManager class. If the peripheral device is still available to be connected to, the central manager calls the centralManager:didConnectPeripheral: method of its delegate object and the peripheral device is successfully reconnected.
Note: A peripheral device may not be available to be connected to for a few reasons. For instance, the device may not be in the vicinity of the central. In addition, some Bluetooth low energy devices use a random device address that changes periodically. Therefore, even if the device is nearby, the address of the device may have changed since the last time it was discovered by the system, in which case the CBPeripheral object you are trying to connect to doesn’t correspond to the actual peripheral device. If you cannot reconnect to the peripheral because its address has changed, you must rediscover it using the scanForPeripheralsWithServices:options: method.
最佳答案
在应用程序启动时，我只会发现所有外围设备，然后将发现的外围设备与数据库中存储的外围设备标识符进行比较。
在比较发现的外围设备和外围设备之后，可以进行所需外围设备的连接。
关于ios - 当用户从后台手动退出应用程序时，如何检索BLE外设？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/39930889/