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Copyright 2013 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.
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Uses the Gravity sensor to count how many jumping jacks you have performed.
<template src="base-build"/>
<template src="Wear"/>
<common src="logger"/>
<common src="activities"/>
A basic sample showing how to use the Gravity sensor on the wearable device
by counting how many jumping jacks you have performed.
[SensorEventListener][1] offers you methods used for receiving notifications from the
[SensorManager][2] when sensor values have changed.
This example counts how many times Jumping Jakcs are performed by detecting the value
of the Gravity sensor by the following code:
public void onSensorChanged(SensorEvent event) {
detectJump(event.values[0], event.timestamp);
private void detectJump(float xValue, long timestamp) {
if ((Math.abs(xValue) > GRAVITY_THRESHOLD)) {
if(timestamp - mLastTime < TIME_THRESHOLD_NS && mUp != (xValue > 0)) {
mUp = xValue > 0;
mLastTime = timestamp;
The detectJump method above assumes that when a person is wearing the watch, the x-component of gravity
as measured by the Gravity Sensor is +9.8 when the hand is downward and -9.8 when the hand
is upward (signs are reversed if the watch is worn on the right hand). Since the upward or
downward may not be completely accurate, we leave some room and instead of 9.8, we use
GRAVITY_THRESHOLD (7.0f). We also consider the up <-> down movement successful if it takes less than
TIME_THRESHOLD_NS (2000000000 nanoseconds).