ios - 当用户从后台手动退出应用程序时如何检索 BLE 外设？

Question

解释:

我正在使用核心蓝牙框架连接到 BTLE 外围设备，将外围设备标识符保存在数据库中。
同时，我将外围设备保存在一个数组中以处理与外围设备的重新连接。
但是，当用户手动退出应用程序时，我的数组变为空。
因此我将无法再次重新连接这些外围设备。

现在，我的数据库中有外围设备标识符。
我已经阅读了它，发现有一个委托(delegate)方法

- (NSArray<CBPeripheral *> *)retrievePeripheralsWithIdentifiers:(NSArray<NSUUID *> *)identifiers NS_AVAILABLE(NA, 7_0)

要获取外围设备，但它没有任何返回。

我如何才能再次获取外围设备？

https://developer.apple.com/library/content/documentation//NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/BestPracticesForInteractingWithARemotePeripheralDevice/BestPracticesForInteractingWithA

我也检查了上面的文件。因为他们提到了重新连接到外围设备的方法

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.

Answer 1

在应用程序启动时，我会发现所有外围设备，然后将发现的外围设备与存储在数据库中的外围设备标识符进行比较。

将发现的外设与外设进行比对后，即可进行所需外设的连接。