Javascript Bluetooth manager组件侦听器函数中的问题处理异步函数

我在蓝牙RN应用程序中运行一些异步代码时遇到问题

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

此侦听器功能作为蓝牙低能（ble）设备扫描功能的参数提供：

// 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 })
        }
    }

解决方案更新： 非常感谢Jaromanda X提供的解决方案

修复方法是在connectToDevice（）和cancelDeviceConnection（）异步函数被拒绝且侦听器将返回时，在其周围添加try捕获（因此，为什么从未打印“连接到设备”日志）

---

@Jaromanda X提供了解决方案：

修复方法是在connectToDevice（）和cancelDeviceConnection（）异步函数被拒绝且侦听器将返回时，在其周围添加try捕获（因此，为什么从未打印“连接到设备”日志）

---

如果console.log从未发生过，那么

bleManager.connectToDevice（device.id）

将永远不会解决（它可能会拒绝，您不会在那里处理错误）-可能会在

async（error，device）=>{

callback中添加try/catch。您完全正确，我在这两种方法上都添加了try-catch，现在就可以了！非常感谢您！

[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
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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
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_callImmediatesPass@http://10.0.0.122:8081/index.bundle?platform=ios&dev=true&minify=false:30363:17
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__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]

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")
                    }
                }
            )

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")
                    }
                }
            )