| /* |
| * Copyright (C) 2008 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.hardware; |
| |
| /** |
| * <p> |
| * This class represents a {@link android.hardware.Sensor Sensor} event and |
| * holds informations such as the sensor's type, the time-stamp, accuracy and of |
| * course the sensor's {@link SensorEvent#values data}. |
| * </p> |
| * |
| * <p> |
| * <u>Definition of the coordinate system used by the SensorEvent API.</u> |
| * </p> |
| * |
| * <p> |
| * The coordinate-system is defined relative to the screen of the phone in its |
| * default orientation. The axes are not swapped when the device's screen |
| * orientation changes. |
| * </p> |
| * |
| * <p> |
| * The X axis is horizontal and points to the right, the Y axis is vertical and |
| * points up and the Z axis points towards the outside of the front face of the |
| * screen. In this system, coordinates behind the screen have negative Z values. |
| * </p> |
| * |
| * <p> |
| * <center><img src="../../../images/axis_device.png" |
| * alt="Sensors coordinate-system diagram." border="0" /></center> |
| * </p> |
| * |
| * <p> |
| * <b>Note:</b> This coordinate system is different from the one used in the |
| * Android 2D APIs where the origin is in the top-left corner. |
| * </p> |
| * |
| * @see SensorManager |
| * @see SensorEvent |
| * @see Sensor |
| * |
| */ |
| |
| public class SensorEvent { |
| /** |
| * <p> |
| * The length and contents of the {@link #values values} array depends on |
| * which {@link android.hardware.Sensor sensor} type is being monitored (see |
| * also {@link SensorEvent} for a definition of the coordinate system used). |
| * </p> |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_ACCELEROMETER |
| * Sensor.TYPE_ACCELEROMETER}:</h4> All values are in SI units (m/s^2) |
| * |
| * <ul> |
| * <p> |
| * values[0]: Acceleration minus Gx on the x-axis |
| * </p> |
| * <p> |
| * values[1]: Acceleration minus Gy on the y-axis |
| * </p> |
| * <p> |
| * values[2]: Acceleration minus Gz on the z-axis |
| * </p> |
| * </ul> |
| * |
| * <p> |
| * A sensor of this type measures the acceleration applied to the device |
| * (<b>Ad</b>). Conceptually, it does so by measuring forces applied to the |
| * sensor itself (<b>Fs</b>) using the relation: |
| * </p> |
| * |
| * <b><center>Ad = - ∑Fs / mass</center></b> |
| * |
| * <p> |
| * In particular, the force of gravity is always influencing the measured |
| * acceleration: |
| * </p> |
| * |
| * <b><center>Ad = -g - ∑F / mass</center></b> |
| * |
| * <p> |
| * For this reason, when the device is sitting on a table (and obviously not |
| * accelerating), the accelerometer reads a magnitude of <b>g</b> = 9.81 |
| * m/s^2 |
| * </p> |
| * |
| * <p> |
| * Similarly, when the device is in free-fall and therefore dangerously |
| * accelerating towards to ground at 9.81 m/s^2, its accelerometer reads a |
| * magnitude of 0 m/s^2. |
| * </p> |
| * |
| * <p> |
| * It should be apparent that in order to measure the real acceleration of |
| * the device, the contribution of the force of gravity must be eliminated. |
| * 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> |
| * <p> |
| * <u>Examples</u>: |
| * <ul> |
| * <li>When the device lies flat on a table and is pushed on its left side |
| * toward the right, the x acceleration value is positive.</li> |
| * |
| * <li>When the device lies flat on a table, the acceleration value is |
| * +9.81, which correspond to the acceleration of the device (0 m/s^2) minus |
| * the force of gravity (-9.81 m/s^2).</li> |
| * |
| * <li>When the device lies flat on a table and is pushed toward the sky |
| * with an acceleration of A m/s^2, the acceleration value is equal to |
| * A+9.81 which correspond to the acceleration of the device (+A m/s^2) |
| * minus the force of gravity (-9.81 m/s^2).</li> |
| * </ul> |
| * |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_MAGNETIC_FIELD |
| * Sensor.TYPE_MAGNETIC_FIELD}:</h4> |
| * All values are in micro-Tesla (uT) and measure the ambient magnetic field |
| * in the X, Y and Z axis. |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_GYROSCOPE Sensor.TYPE_GYROSCOPE}:</h4> |
| * All values are in radians/second and measure the rate of rotation |
| * around the X, Y and Z axis. The coordinate system is the same as is |
| * used for the acceleration sensor. Rotation is positive in the counter-clockwise |
| * direction. That is, an observer looking from some positive location on the x, y. |
| * or z axis at a device positioned on the origin would report positive rotation |
| * if the device appeared to be rotating counter clockwise. Note that this is the |
| * 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]: Ambient light level in SI lux units |
| * </ul> |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_PROXIMITY Sensor.TYPE_PROXIMITY}: |
| * </h4> |
| * |
| * <ul> |
| * <p> |
| * values[0]: Proximity sensor distance measured in centimeters |
| * </ul> |
| * |
| * <p> |
| * <b>Note:</b> Some proximity sensors only support a binary <i>near</i> or |
| * <i>far</i> measurement. In this case, the sensor should report its |
| * {@link android.hardware.Sensor#getMaximumRange() maximum range} value in |
| * the <i>far</i> state and a lesser value in the <i>near</i> state. |
| * </p> |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_GRAVITY Sensor.TYPE_GRAVITY}:</h4> |
| * A three dimensional vector indicating the direction and magnitude of gravity. Units |
| * are m/s^2. The coordinate system is the same as is used by the acceleration sensor. |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_LINEAR_ACCELERATION Sensor.TYPE_LINEAR_ACCELERATION}:</h4> |
| * A three dimensional vector indicating acceleration along each device axis, not including |
| * gravity. All values have units of m/s^2. The coordinate system is the same as is used by the |
| * acceleration sensor. |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_ROTATION_VECTOR Sensor.TYPE_ROTATION_VECTOR}:</h4> |
| * The rotation vector represents the orientation of the device as a combination of an angle |
| * and an axis, in which the device has rotated through an angle theta around an axis |
| * <x, y, z>. The three elements of the rotation vector are |
| * <x*sin(theta/2), y*sin(theta/2), z*sin(theta/2)>, such that the magnitude of the rotation |
| * vector is equal to sin(theta/2), and the direction of the rotation vector is equal to the |
| * direction of the axis of rotation. The three elements of the rotation vector are equal to |
| * the last three components of a unit quaternion |
| * <cos(theta/2), x*sin(theta/2), y*sin(theta/2), z*sin(theta/2)>. Elements of the rotation |
| * vector are unitless. The x,y, and z axis are defined in the same way as the acceleration |
| * sensor. |
| * |
| * <h4>{@link android.hardware.Sensor#TYPE_ORIENTATION |
| * Sensor.TYPE_ORIENTATION}:</h4> All values are angles in degrees. |
| * |
| * <ul> |
| * <p> |
| * values[0]: Azimuth, angle between the magnetic north direction and the |
| * y-axis, around the z-axis (0 to 359). 0=North, 90=East, 180=South, |
| * 270=West |
| * </p> |
| * |
| * <p> |
| * values[1]: Pitch, rotation around x-axis (-180 to 180), with positive |
| * values when the z-axis moves <b>toward</b> the y-axis. |
| * </p> |
| * |
| * <p> |
| * values[2]: Roll, rotation around y-axis (-90 to 90), with positive values |
| * when the x-axis moves <b>toward</b> the z-axis. |
| * </p> |
| * </ul> |
| * |
| * <p> |
| * <b>Note:</b> This definition is different from <b>yaw, pitch and roll</b> |
| * used in aviation where the X axis is along the long side of the plane |
| * (tail to nose). |
| * </p> |
| * |
| * <p> |
| * <b>Note:</b> This sensor type exists for legacy reasons, please use |
| * {@link android.hardware.SensorManager#getRotationMatrix |
| * getRotationMatrix()} in conjunction with |
| * {@link android.hardware.SensorManager#remapCoordinateSystem |
| * remapCoordinateSystem()} and |
| * {@link android.hardware.SensorManager#getOrientation getOrientation()} to |
| * compute these values instead. |
| * </p> |
| * |
| * <p> |
| * <b>Important note:</b> For historical reasons the roll angle is positive |
| * in the clockwise direction (mathematically speaking, it should be |
| * positive in the counter-clockwise direction). |
| * </p> |
| * |
| * @see SensorEvent |
| * @see GeomagneticField |
| */ |
| |
| public final float[] values; |
| |
| /** |
| * The sensor that generated this event. See |
| * {@link android.hardware.SensorManager SensorManager} for details. |
| */ |
| public Sensor sensor; |
| |
| /** |
| * The accuracy of this event. See {@link android.hardware.SensorManager |
| * SensorManager} for details. |
| */ |
| public int accuracy; |
| |
| |
| /** |
| * The time in nanosecond at which the event happened |
| */ |
| public long timestamp; |
| |
| |
| SensorEvent(int size) { |
| values = new float[size]; |
| } |
| } |
