我正在尝试为标准 HC-SR04 超声波传感器创建一个 Android Things 驱动程序。我相信我的事件顺序是正确的：请参阅页脚，但无法将其注册为 UserSensor。
userSensor = UserSensor.Builder()
.setName("HC-SR04 Ultrasonic Distance Sensor")
.setVersion(1)
// If boolean "on face or not," should I use something linear like TYPE_LIGHT
.setType(Sensor.TYPE_PROXIMITY)
.setDriver(this) // UserSensorDriver
.build()
此时，将 UserSensor 注册到 UserDriverManager（完成）和将其注册到 SensorManager 有什么区别？是否有任何东西阻止它出现在传感器列表中？我是否需要像 sensorManager.registerDynamicSensorCallback 一样等到传感器“准备好”？
val sensorManager = context.getSystemService(Context.SENSOR_SERVICE) as SensorManager
sensorManager.registerListener(this, // SensorEventListener.onSensorChanged
sensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY),
SensorManager.SENSOR_DELAY_NORMAL)
无论我尝试什么，我都会得到“E/SensorManager: sensor or listener is null”（这在 Kotlin 中更令人惊讶，因为 null 不应该潜入太多）
我的传感器/也是一个要点：
/** Callback for when the distance changes "enough to care" */
interface SignificantDistanceChangeListener {
fun onDistanceChanged(distanceCm: Float)
}
/**
* User Sensor - Ultrasonic range finder
*/
class HCSR04(context: Context, val sdcl: SignificantDistanceChangeListener) : UserSensorDriver(), SensorEventListener, AutoCloseable {
private val LOG = Logger.getLogger(this.javaClass.name)
private val gpio = PeripheralManagerService().openGpio("BCM23")
private val distanceReading: BlockingQueue<Float> = ArrayBlockingQueue(1)
// Choreography of each ping
private val scheduler: ScheduledExecutorService = Executors.newScheduledThreadPool(1)
private val userSensor: UserSensor
init {
userSensor = UserSensor.Builder()
.setName("HC-SR04 Ultrasonic Distance Sensor")
.setVersion(1)
.setType(Sensor.TYPE_PROXIMITY) // Could this be something more linear like TYPE_LIGHT
.setDriver(this)
.build()
UserDriverManager.getManager().registerSensor(userSensor)
val sensorManager = context.getSystemService(Context.SENSOR_SERVICE) as SensorManager
LOG.info("ALL Sensors: ${sensorManager.getSensorList(Sensor.TYPE_ALL)}")
sensorManager.registerDynamicSensorCallback(object : SensorManager.DynamicSensorCallback() {
override fun onDynamicSensorConnected(sensor: Sensor) {
LOG.info("onDynamicSensorConnected")
if (sensor.type == Sensor.TYPE_PROXIMITY) {
sensorManager.registerListener(
this@HCSR04,
sensor,
SensorManager.SENSOR_DELAY_NORMAL
)
}
}
})
}
val gpioEdgeCallback = object : GpioCallback() {
// Track the reply rise/fall
private val startMs = AtomicLong()
private val startValid = AtomicBoolean(false)
private fun calculate() {
val elapsed = (System.nanoTime() / 1000) - startMs.get()
if (startValid.get() && elapsed > 0) {
distanceReading.put(elapsed * 34000 / 2f)
} else {
LOG.warning("Discarding edge callback ${startMs.get()} ${startValid.get()} $elapsed")
}
startValid.set(false)
}
override fun onGpioEdge(gpio: Gpio?): Boolean {
if (gpio != null) {
if (gpio.value) {
startMs.set(System.nanoTime() / 1000)
startValid.set(true)
} else {
calculate()
}
LOG.finer("GPIO input edge: ${System.nanoTime() / 1000} ${gpio.value}")
}
return true
}
override fun onGpioError(gpio: Gpio?, error: Int) = LOG.severe("$gpio Error event $error")
}
/** Launch a new thread to get the distance, then block until we have a result */
override fun read(): UserSensorReading {
distanceReading.clear()
gpio.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW)
gpio.setActiveType(Gpio.ACTIVE_HIGH)
gpio.value = false
scheduler.schedule({ gpio.value = true }, 1, TimeUnit.MICROSECONDS)
scheduler.schedule({ gpio.value = false }, 11, TimeUnit.MICROSECONDS)
scheduler.schedule({
gpio.setDirection(Gpio.DIRECTION_IN)
gpio.setActiveType(Gpio.ACTIVE_HIGH) // redundant?
gpio.setEdgeTriggerType(Gpio.EDGE_BOTH)
gpio.registerGpioCallback(gpioEdgeCallback)
}, 12, TimeUnit.MICROSECONDS)
val distanceCm = distanceReading.take()
gpio.unregisterGpioCallback(gpioEdgeCallback)
LOG.info("New distance reading: $distanceCm")
return UserSensorReading(floatArrayOf(distanceCm))
}
/** from @SensorEventListener */
override fun onAccuracyChanged(sensor: Sensor, accuracy: Int) = LOG.info("$sensor accuracy change: $accuracy")
/**
* from @SensorEventListener
*/
override fun onSensorChanged(event: SensorEvent) = sdcl.onDistanceChanged(event.values[0])
/** from @AutoCloseable */
override fun close() {
LOG.warning("Closing Sensor HCSR04")
UserDriverManager.getManager().unregisterSensor(userSensor)
gpio.close()
scheduler.shutdownNow()
}
}