ios - 蓝牙 BLE 状态保存：CBCentralManager 在后台不会发现服务

Question

编辑： 在@RobertVaessen 评论之后，我实现了以下内容，但是我仍然无法发现连接的外围设备的服务。

-(void) centralManager:(CBCentralManager *)central willRestoreState:(NSDictionary<NSString *,id> *)dict{

    id tmpObj = [dict objectForKey:CBCentralManagerRestoredStatePeripheralsKey];

    NSArray * keys = [dict allKeys];
    NSString * message = @"";
    for (int i=0; i<[keys count]; i++) {
        NSString * stringTmp = keys[i];
        message = [message stringByAppendingString:@";"];
        message = [message stringByAppendingString:stringTmp];
    }

    // message contains "kCBRestoredScanServices and kCBRestoredPeripherals

    if ([tmpObj isKindOfClass:[NSArray class]]) {
        NSArray * peripheralsArray = (NSArray*)tmpObj;

        for (int i=0; i<[peripheralsArray count]; i++) {
            id objTmp = peripheralsArray[i];
            if ([objTmp isKindOfClass:[CBPeripheral class]]) {
                CBPeripheral * tmpPeripheral = (CBPeripheral*)objTmp;
                 tmpPeripheral.delegate = self;
                [tmpPeripheral discoverServices: self.bleServices];
                // It would reach this part of the code but not discover any services
            }
        }
     }
}

现在的疑问是：

当应用程序处于前台并首次连接到外围设备时，我已经发现了服务，这是否意味着一旦应用程序再次被唤醒，CBCentralManager 将无法发现服务？

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理论背景：

此处描述了蓝牙 LE 状态保存过程（请参阅“添加对状态保存和恢复的支持”部分）：

https://developer.apple.com/library/ios/documentation/NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/CoreBluetoothBackgroundProcessingForIOSApps/PerformingTasksWhileYourAppIsInTheBackground.html

我正在尝试做的事情：

我正在实现一个应用程序，它使用BLE 状态保存来保持与硬件附件的连接（在后台运行时）。

我遇到的问题是，每当iOS 在 BLE 状态保存事件之后唤醒我的应用程序时，我的 CBCentralManager 都无法发现这些服务。奇怪的是，硬件外围设备“看到”了连接，但 iOS 应用程序无法访问它。

换句话说： 实现 CBCentralManager 委托的类中的以下方法被正确调用，但作用不大（请参见下面的绿色注释）：

-(void) centralManager:(CBCentralManager *)central willRestoreState:(NSDictionary<NSString *,id> *)dict{  
    NSArray * peripherals = [self.central retrieveConnectedPeripheralsWithServices:self.bleServices];  

    for (int i=0; i < peripherals.count; i++) {  
        CBPeripheral * peripheral = (CBPeripheral*) peripherals[i];  

        if (peripheral == nil) {  
            // Never happens  
        }  
        else{  
            // Always happens - also hardware thinks that the peripheral is connected  
            peripheral.delegate = self;  
            [peripheral discoverServices:self.bleServices];  

            // Does not discover any services !  <------------- ERROR!  
        }  
} 





-(void) peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {  
// Only gets called when [peripheral discoverServices:self.bleServices] is called whilst app is running (either in background or foreground).  
}  

PS：我也在苹果开发者论坛上问过这个问题，但到目前为止还没有回复。

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PPS： 我还在 info.plist 文件中激活了后台模式：