am b48189cc: Merge "Improve gyro and accelerometer java doc" into gingerbread (0e438287) · Commits · e / os / android_frameworks_base

core/java/android/hardware/SensorEvent.java

+55 −1

Original line number	Diff line number	Diff line
		@@ -111,6 +111,27 @@ public class SensorEvent {
		* This can be achieved by applying a <i>high-pass</i> filter. Conversely, a
		* <i>low-pass</i> filter can be used to isolate the force of gravity.
		* </p>
		*
		* <pre class="prettyprint">
		*
		* public void onSensorChanged(SensorEvent event)
		* {
		* // alpha is calculated as t / (t + dT)
		* // with t, the low-pass filter's time-constant
		* // and dT, the event delivery rate
		*
		* final float alpha = 0.8;
		*
		* gravity[0] = alpha * gravity[0] + (1 - alpha) * event.data[0];
		* gravity[1] = alpha * gravity[1] + (1 - alpha) * event.data[1];
		* gravity[2] = alpha * gravity[2] + (1 - alpha) * event.data[2];
		*
		* linear_acceleration[0] = event.data[0] - gravity[0];
		* linear_acceleration[1] = event.data[1] - gravity[1];
		* linear_acceleration[2] = event.data[2] - gravity[2];
		* }
		* </pre>
		*
		* <p>
		* <u>Examples</u>:
		* <ul>
		@@ -143,8 +164,41 @@ public class SensorEvent {
		* standard mathematical definition of positive rotation and does not agree with the
		* definition of roll given earlier.
		*
		* <h4>{@link android.hardware.Sensor#TYPE_LIGHT Sensor.TYPE_LIGHT}:</h4>
		* <ul>
		* <p>
		* values[0]: Angular speed around the x-axis
		* </p>
		* <p>
		* values[1]: Angular speed around the y-axis
		* </p>
		* <p>
		* values[2]: Angular speed around the z-axis
		* </p>
		* </ul>
		* <p>
		* Typically the output of the gyroscope is integrated over time to calculate
		* an angle, for example:
		* </p>
		* <pre class="prettyprint">
		* private static final float NS2S = 1.0f / 1000000000.0f;
		* private float timestamp;
		* public void onSensorChanged(SensorEvent event)
		* {
		* if (timestamp != 0) {
		* final float dT = (event.timestamp - timestamp) * NS2S;
		* angle[0] += event.data[0] * dT;
		* angle[1] += event.data[1] * dT;
		* angle[2] += event.data[2] * dT;
		* }
		* timestamp = event.timestamp;
		* }
		* </pre>
		*
		* <p>In practice, the gyroscope noise and offset will introduce some errors which need
		* to be compensated for. This is usually done using the information from other
		* sensors, but is beyond the scope of this document.</p>
		*
		* <h4>{@link android.hardware.Sensor#TYPE_LIGHT Sensor.TYPE_LIGHT}:</h4>
		* <ul>
		* <p>
		* values[0]: Ambient light level in SI lux units