在 Android 中，如何指定 BLE ScanCallback 在哪个线程上运行？

问：

人造人。科特林。

您好，我希望能帮助理解线程在这里的工作原理:)

我有一个 BLE 扫描仪类。它的方法使用 运行所有内容。我设法确认它的代码不在主线程上运行。在它里面我创造了一个，在里面我创造了一个.我假设回调的方法将在创建回调的同一线程上运行。但事实并非如此 - 它在主线程上运行，可能会阻塞 UI。scan()Dispatcher.IOsuspendCancellableCoroutineScanCallback

问题：有没有办法确保 s 方法与其余方法运行在同一线程上？ScanCallback'onScanResultonScanFailedFakeScaner.scan()

原因：在某些情况下，我需要停止扫描仪，休眠几秒钟，然后重新启动它。我设法做了一个解决方法，但我仍然想弄清楚为什么它有效，以及如何在可能的情况下更改它:)

class FakeScanner(
    private val context: Context,
    private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO) {

    private val bluetoothAdapter: BluetoothAdapter by lazy {
        val bluetoothManager = context.getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager
        requireNotNull(bluetoothManager.adapter)
    }

    suspend fun scan(timeout: Duration?): Map<MyDevice, SignalStrength> =
        withContext(ioDispatcher) {
            if (Looper.myLooper() == Looper.getMainLooper()) {
                Log.d(TAG, "This is running MAIN thread")
            } else {
                Log.d(TAG, "This is running NOT on MAIN thread")
            }

            /**
             * Some code here
             */

            suspendCancellableCoroutine { cont ->

                val bleDevices = mutableMapOf<BluetoothDevice, SignalStrength>()

                val scanCallback = object : ScanCallback() {

                    @Synchronized
                    override fun onScanResult(callbackType: Int, result: ScanResult?) {

                        if (Looper.myLooper() == Looper.getMainLooper()) {
                            Log.d(TAG, "This is running MAIN thread")
                        } else {
                            Log.d(TAG, "This is running NOT on MAIN thread")
                        }

                        try {
                            result?.device?.let {
                                bleDevices.put(it, SignalStrength(result.rssi))
                            }
                        } catch (t: Throwable) {
                            if (cont.isActive) { cont.resumeWithException(t) }
                        }
                    }

                    @Synchronized
                    override fun onScanFailed(errorCode: Int) {
                        try {
                            // Some logic about scan attempt limits..
                            when (errorCode) {
                                SCAN_FAILED_ALREADY_STARTED -> { /* Restart scanner after delay */ }
                                else -> { /* Logic about other error codes */ }
                            }
                        } catch (t: Throwable) {
                            if (cont.isActive) { cont.resumeWithException(t) }
                        }
                    }
                }

                try {
                    // Start scanning
                } catch (t: Throwable) {
                    if (cont.isActive) {
                        cont.resumeWithException(t)
                    }
                }

                cont.invokeOnCancellation {
                    try {
                        // Stop scanner here
                    } catch (t: SecurityException) {
                        // Nothing to do here
                    }
                }
            }
        }
}