93 lines
3.2 KiB
Markdown
93 lines
3.2 KiB
Markdown
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Android JumpingJack Sample
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===================================
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A basic sample showing how to use the Gravity sensor on the wearable device
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by counting how many jumping jacks you have performed.
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Introduction
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------------
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[SensorEventListener][1] offers you methods used for receiving notifications from the
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[SensorManager][2] when sensor values have changed.
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This example counts how many times Jumping Jacks are performed by detecting the value
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of the Gravity sensor by the following code:
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```java
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@Override
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public void onSensorChanged(SensorEvent event) {
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detectJump(event.values[0], event.timestamp);
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}
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private void detectJump(float xValue, long timestamp) {
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if ((Math.abs(xValue) > GRAVITY_THRESHOLD)) {
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if(timestamp - mLastTime < TIME_THRESHOLD_NS && mUp != (xValue > 0)) {
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onJumpDetected(!mUp);
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}
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mUp = xValue > 0;
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mLastTime = timestamp;
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}
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}
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```
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The detectJump method above assumes that when a person is wearing the watch, the x-component of gravity
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as measured by the Gravity Sensor is +9.8 when the hand is downward and -9.8 when the hand
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is upward (signs are reversed if the watch is worn on the right hand). Since the upward or
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downward may not be completely accurate, we leave some room and instead of 9.8, we use
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GRAVITY_THRESHOLD (7.0f). We also consider the up <-> down movement successful if it takes less than
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TIME_THRESHOLD_NS (2000000000 nanoseconds).
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[1]: http://developer.android.com/reference/android/hardware/SensorEventListener.html
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[2]: http://developer.android.com/reference/android/hardware/SensorManager.html
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Pre-requisites
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--------------
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- Android SDK 27
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- Android Build Tools v27.0.2
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- Android Support Repository
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Screenshots
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-------------
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<img src="screenshots/jumping_jack.gif" height="400" alt="Screenshot"/>
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Getting Started
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---------------
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This sample uses the Gradle build system. To build this project, use the
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"gradlew build" command or use "Import Project" in Android Studio.
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Support
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-------
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- Google+ Community: https://plus.google.com/communities/105153134372062985968
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- Stack Overflow: http://stackoverflow.com/questions/tagged/android
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If you've found an error in this sample, please file an issue:
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https://github.com/googlesamples/android-JumpingJack
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Patches are encouraged, and may be submitted by forking this project and
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submitting a pull request through GitHub. Please see CONTRIBUTING.md for more details.
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License
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-------
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Copyright 2017 The Android Open Source Project, Inc.
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Licensed to the Apache Software Foundation (ASF) under one or more contributor
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license agreements. See the NOTICE file distributed with this work for
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additional information regarding copyright ownership. The ASF licenses this
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file to you under the Apache License, Version 2.0 (the "License"); you may not
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use this file except in compliance with the License. You may obtain a copy of
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the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations under
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the License.
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