蓝牙管理器组件侦听器函数中的问题处理异步函数

Question

我遇到问题运行蓝牙 RN 应用程序中的一些异步代码。

我正在尝试创建一个执行以下操作的侦听器函数：连接到设备（使用异步函数），记录我已连接，然后断开与设备的连接（使用异步函数）。

此侦听器函数作为参数提供给蓝牙低功耗 (ble) 设备扫描函数：

// Relevant Function Prototypes --------------------------------------------------

// startDeviceScan() -> This scans for devices and runs a listener function on each
//                      device it scans. 
bleManager.startDeviceScan(
  UUIDs: ?Array<UUID>,
  options: ?ScanOptions,
  listener: (error: ?Error, scannedDevice: ?Device) => void // <- this listener function
)
// connectToDevice() -> This connects to a device scanned by the bleManager in the 
//                      listener function given to startDeviceScan()
bleManager.connectToDevice(
  deviceIdentifier: DeviceId,
  options: ?ConnectionOptions,
): Promise<Device>

// My code ------------------------------------------------------------------------

// Scans nearby ble devices advertising and runs a listener function that has the 
//  connection error status and device id as given parameters.
// **This function triggers on a Button onPress
 const handleStartScanning = async () => {
        try {
            bleManager.startDeviceScan(
                ['00001200-0000-1000-8000-00805f9b34fb'], // the service UUID I am scanning for
                { allowDuplicates: true }, // I allow to duplicates to continuously reconnect to devices
                async (error, device) => {

                    // get services
                    let services = device.serviceUUIDs // get list of the service UUIDs on device

                    // make sure services not null and out service UUID is included
                    if (services && services.includes('00001200-0000-1000-8000-00805f9b34fb')) {

                        // log the scanned device's name, rssi, and its service UUIDs                        
                        console.log("Scanned a device with name: " + device.name + " | " + device.rssi)
                        console.log("Services:", services)
                        await bleManager.connectToDevice(device.id) // <- *****ISSUE HERE*****
                        console.log("Connected to device") // <- *****THIS NEVER PRINTS*****
                        // run some more async code here once i'm connected to the device
                        await bleManager.cancelDeviceConnection(device.id)
                    }
                }
            )
        } catch (error) {
            console.log('Could not start scanning for devices', { error })
        }
    }

我不明白为什么即使我使侦听器函数异步并等待侦听器中的 2 个异步函数调用，Connected to Device 日志也不会打印。这意味着侦听器永远不会在 await bleManager.connectToDevice(device.id) 异步函数调用

之后执行

这是我的控制台日志：

注意 Possible Unhandled Promise Rejection (id: 150): BleError: Operation was cancelled 在我发布下面的代码片段后重复输入错误日志。有时日志会返回到某些设备中的扫描，但总是会返回到承诺拒绝。 Connected to device console.log 从不打印。

[Thu Oct 01 2020 22:59:42.385]  LOG      Scanned a device with name: Android | -43
[Thu Oct 01 2020 22:59:42.387]  LOG      Services: ["00001200-0000-1000-8000-00805f9b34fb"]
[Thu Oct 01 2020 22:59:42.388]  LOG      Scanned a device with name: Android | -43
[Thu Oct 01 2020 22:59:42.388]  LOG      Services: ["00001200-0000-1000-8000-00805f9b34fb"]
[Thu Oct 01 2020 22:59:42.487]  LOG      Scanned a device with name: Android | -44
[Thu Oct 01 2020 22:59:42.491]  LOG      Services: ["00001200-0000-1000-8000-00805f9b34fb"]
[Thu Oct 01 2020 22:59:42.492]  LOG      Scanned a device with name: Android | -44
[Thu Oct 01 2020 22:59:42.492]  LOG      Services: ["00001200-0000-1000-8000-00805f9b34fb"]
[Thu Oct 01 2020 22:59:42.514]  WARN     Possible Unhandled Promise Rejection (id: 150):
BleError: Operation was cancelled
construct@[native code]
_construct@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:23889:28
Wrapper@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:23844:25
construct@[native code]
_createSuperInternal@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:117317:322
BleError@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:117330:26
parseBleError@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:117368:30
_callPromise$@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:117632:51
tryCatch@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:24712:23
invoke@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:24885:32
tryCatch@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:24712:23
invoke@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:24785:30
http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:24797:21
tryCallOne@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:26784:16
http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:26885:27
_callTimer@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:30324:17
_callImmediatesPass@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:30363:17
callImmediates@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:30580:33
__callImmediates@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:2630:35
http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:2416:34
__guard@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:2613:15
flushedQueue@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:2415:21
flushedQueue@[native code]
invokeCallbackAndReturnFlushedQueue@[native code]

解决方案更新：非常感谢 Jaromanda X 提供解决方案！

解决方法是在 connectToDevice() 和 cancelDeviceConnection() 异步函数周围添加尝试捕获，因为它们被拒绝并且侦听器会 return（因此 'Connected to Device' 日志从未打印过).

bleManager.startDeviceScan(
                ['00001200-0000-1000-8000-00805f9b34fb'],
                { allowDuplicates: true },
                async (error, device) => {
                    // get services
                    let services = device.serviceUUIDs
                    // check if there are services being advertised
                    if (services && services.includes('00001200-0000-1000-8000-00805f9b34fb')) {
                        console.log("Scanned a device with name: " + device.name + " | " + device.rssi)
                        console.log("Services:", services)
                        try {
                            await bleManager.connectToDevice(device.id)
                        } catch {
                            console.log("Could not connect")
                        }
                        console.log("Connected to device: ", device.name)
                        // run some more async code once i'm connected to the device
                        try {
                            await bleManager.cancelDeviceConnection(device.id)
                        } catch {
                            console.log("Could not disconnect")
                        }
                        // await bleManager.connectToDevice(device.id)
                        //console.log("Connected to device")
                        //await bleManager.cancelDeviceConnection(device.id)
                        //console.log("Disconnected from device")
                    }
                }
            )

Answer 1

@Jaromanda X 提供了解决方案：

解决方法是在 connectToDevice() 和 cancelDeviceConnection() 异步函数周围添加尝试捕获，因为它们被拒绝并且侦听器会 return（因此 'Connected to Device' 日志从未打印过).

bleManager.startDeviceScan(
                ['00001200-0000-1000-8000-00805f9b34fb'],
                { allowDuplicates: true },
                async (error, device) => {
                    // get services
                    let services = device.serviceUUIDs
                    // check if there are services being advertised
                    if (services && services.includes('00001200-0000-1000-8000-00805f9b34fb')) {
                        console.log("Scanned a device with name: " + device.name + " | " + device.rssi)
                        console.log("Services:", services)
                        try {
                            await bleManager.connectToDevice(device.id)
                        } catch {
                            console.log("Could not connect")
                        }
                        console.log("Connected to device: ", device.name)
                        // run some more async code once i'm connected to the device
                        try {
                            await bleManager.cancelDeviceConnection(device.id)
                        } catch {
                            console.log("Could not disconnect")
                        }
                        // await bleManager.connectToDevice(device.id)
                        //console.log("Connected to device")
                        //await bleManager.cancelDeviceConnection(device.id)
                        //console.log("Disconnected from device")
                    }
                }
            )

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