SensorDirectChannel

class SensorDirectChannel : Channel

RATE_FAST

static val RATE_FAST: Int

Sensor operates at nominal rate of 200Hz. The actual rate is expected to be between 55% to 220% of nominal rate, thus between 110Hz to 440Hz.

Value: 2

RATE_NORMAL

static val RATE_NORMAL: Int

Sensor operates at nominal rate of 50Hz. The actual rate is expected to be between 55% to 220% of nominal rate, thus between 27.5Hz to 110Hz.

Value: 1

RATE_STOP

static val RATE_STOP: Int

Sensor stopped (no event output).

Value: 0

RATE_VERY_FAST

static val RATE_VERY_FAST: Int

Sensor operates at nominal rate of 800Hz. The actual rate is expected to be between 55% to 220% of nominal rate, thus between 440Hz to 1760Hz.

Value: 3

TYPE_HARDWARE_BUFFER

static val TYPE_HARDWARE_BUFFER: Int

Shared memory type wrapped by HardwareBuffer object.

Value: 2

TYPE_MEMORY_FILE

static val TYPE_MEMORY_FILE: Int

Shared memory type ashmem, wrapped in MemoryFile object.

Value: 1

close

fun close(): Unit

Close sensor direct channel. Stop all active sensor in the channel and free sensor system resource related to channel. Shared memory used for creating the direct channel need to be closed or freed separately.

Exceptions
java.lang.Exception	if this resource cannot be closed
java.io.IOException	If an I/O error occurs

configure

fun configure(
    sensor: Sensor!, 
    rateLevel: Int
): Int

Configure sensor rate or stop sensor report. To start event report of a sensor, or change rate of existing report, call this function with rateLevel other than android.hardware.SensorDirectChannel#RATE_STOP. Sensor events will be added into a queue formed by the shared memory used in creation of direction channel. Each element of the queue has size of 104 bytes and represents a sensor event. Data structure of an element (all fields in little-endian):

offset   type                    name
  ------------------------------------------------------------------------
    0x0000   int32_t                 size (always 104)
    0x0004   int32_t                 sensor report token
    0x0008   int32_t                 type (see SensorType)
    0x000C   uint32_t                atomic counter
    0x0010   int64_t                 timestamp (see Event)
    0x0018   float[16]/int64_t[8]    data (data type depends on sensor type)
    0x0058   int32_t[4]              reserved (set to zero)
  

There are no head or tail pointers. The sequence and frontier of new sensor events is determined by the atomic counter, which counts from 1 after creation of direct channel and increments 1 for each new event. Atomic counter will wrap back to 1 after it reaches UINT32_MAX, skipping value 0 to avoid confusion with uninitialized memory. The writer in sensor system will wrap around from the start of shared memory region when it reaches the end. If size of memory region is not a multiple of size of element (104 bytes), the residual is not used at the end. Function returns a positive sensor report token on success. This token can be used to differentiate sensor events from multiple sensor of the same type. For example, if there are two accelerometers in the system A and B, it is guaranteed different report tokens will be returned when starting sensor A and B. To stop a sensor, call this function with rateLevel equal android.hardware.SensorDirectChannel#RATE_STOP. If the sensor parameter is left to be null, this will stop all active sensor report associated with the direct channel specified. Function return 1 on success or 0 on failure.

Parameters
sensor	Sensor!: A android.hardware.Sensor object to denote sensor to be operated.
rateLevel	Int: rate level defined in android.hardware.SensorDirectChannel. Value is android.hardware.SensorDirectChannel#RATE_STOP, android.hardware.SensorDirectChannel#RATE_NORMAL, android.hardware.SensorDirectChannel#RATE_FAST, or android.hardware.SensorDirectChannel#RATE_VERY_FAST

Return
Int	* starting report or changing rate: positive sensor report token on success, 0 on failure; * stopping report: 1 on success, 0 on failure.

Exceptions
java.lang.NullPointerException	when channel is null.

isOpen

fun isOpen(): Boolean

Determine if a channel is still valid. A channel is invalidated after #close() is called.

Return
Boolean	true if channel is valid.

finalize

protected fun finalize(): Unit

Exceptions
java.lang.Throwable	the Exception raised by this method